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- Network Working Group S. Andersen
- Request for Comments: 3951 Aalborg University
- Category: Experimental A. Duric
- Telio
- H. Astrom
- R. Hagen
- W. Kleijn
- J. Linden
- Global IP Sound
- December 2004
- Internet Low Bit Rate Codec (iLBC)
- Status of this Memo
- This memo defines an Experimental Protocol for the Internet
- community. It does not specify an Internet standard of any kind.
- Discussion and suggestions for improvement are requested.
- Distribution of this memo is unlimited.
- Copyright Notice
- Copyright (C) The Internet Society (2004).
- Abstract
- This document specifies a speech codec suitable for robust voice
- communication over IP. The codec is developed by Global IP Sound
- (GIPS). It is designed for narrow band speech and results in a
- payload bit rate of 13.33 kbit/s for 30 ms frames and 15.20 kbit/s
- for 20 ms frames. The codec enables graceful speech quality
- degradation in the case of lost frames, which occurs in connection
- with lost or delayed IP packets.
- Andersen, et al. Experimental [Page 1]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Table of Contents
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
- 2. Outline of the Codec . . . . . . . . . . . . . . . . . . . . . 5
- 2.1. Encoder. . . . . . . . . . . . . . . . . . . . . . . . . 5
- 2.2. Decoder. . . . . . . . . . . . . . . . . . . . . . . . . 7
- 3. Encoder Principles . . . . . . . . . . . . . . . . . . . . . . 7
- 3.1. Pre-processing . . . . . . . . . . . . . . . . . . . . . 9
- 3.2. LPC Analysis and Quantization. . . . . . . . . . . . . . 9
- 3.2.1. Computation of Autocorrelation Coefficients. . . 10
- 3.2.2. Computation of LPC Coefficients. . . . . . . . . 11
- 3.2.3. Computation of LSF Coefficients from LPC
- Coefficients . . . . . . . . . . . . . . . . . . 11
- 3.2.4. Quantization of LSF Coefficients . . . . . . . . 12
- 3.2.5. Stability Check of LSF Coefficients. . . . . . . 13
- 3.2.6. Interpolation of LSF Coefficients. . . . . . . . 13
- 3.2.7. LPC Analysis and Quantization for 20 ms Frames . 14
- 3.3. Calculation of the Residual. . . . . . . . . . . . . . . 15
- 3.4. Perceptual Weighting Filter. . . . . . . . . . . . . . . 15
- 3.5. Start State Encoder. . . . . . . . . . . . . . . . . . . 15
- 3.5.1. Start State Estimation . . . . . . . . . . . . . 16
- 3.5.2. All-Pass Filtering and Scale Quantization. . . . 17
- 3.5.3. Scalar Quantization. . . . . . . . . . . . . . . 18
- 3.6. Encoding the Remaining Samples . . . . . . . . . . . . . 19
- 3.6.1. Codebook Memory. . . . . . . . . . . . . . . . . 20
- 3.6.2. Perceptual Weighting of Codebook Memory
- and Target . . . . . . . . . . . . . . . . . . . 22
- 3.6.3. Codebook Creation. . . . . . . . . . . . . . . . 23
- 3.6.3.1. Creation of a Base Codebook . . . . . . 23
- 3.6.3.2. Codebook Expansion. . . . . . . . . . . 24
- 3.6.3.3. Codebook Augmentation . . . . . . . . . 24
- 3.6.4. Codebook Search. . . . . . . . . . . . . . . . . 26
- 3.6.4.1. Codebook Search at Each Stage . . . . . 26
- 3.6.4.2. Gain Quantization at Each Stage . . . . 27
- 3.6.4.3. Preparation of Target for Next Stage. . 28
- 3.7. Gain Correction Encoding . . . . . . . . . . . . . . . . 28
- 3.8. Bitstream Definition . . . . . . . . . . . . . . . . . . 29
- 4. Decoder Principles . . . . . . . . . . . . . . . . . . . . . . 32
- 4.1. LPC Filter Reconstruction. . . . . . . . . . . . . . . . 33
- 4.2. Start State Reconstruction . . . . . . . . . . . . . . . 33
- 4.3. Excitation Decoding Loop . . . . . . . . . . . . . . . . 34
- 4.4. Multistage Adaptive Codebook Decoding. . . . . . . . . . 35
- 4.4.1. Construction of the Decoded Excitation Signal. . 35
- 4.5. Packet Loss Concealment. . . . . . . . . . . . . . . . . 35
- 4.5.1. Block Received Correctly and Previous Block
- Also Received. . . . . . . . . . . . . . . . . . 35
- 4.5.2. Block Not Received . . . . . . . . . . . . . . . 36
- Andersen, et al. Experimental [Page 2]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4.5.3. Block Received Correctly When Previous Block
- Not Received . . . . . . . . . . . . . . . . . . 36
- 4.6. Enhancement. . . . . . . . . . . . . . . . . . . . . . . 37
- 4.6.1. Estimating the Pitch . . . . . . . . . . . . . . 39
- 4.6.2. Determination of the Pitch-Synchronous
- Sequences. . . . . . . . . . . . . . . . . . . . 39
- 4.6.3. Calculation of the Smoothed Excitation . . . . . 41
- 4.6.4. Enhancer Criterion . . . . . . . . . . . . . . . 41
- 4.6.5. Enhancing the Excitation . . . . . . . . . . . . 42
- 4.7. Synthesis Filtering. . . . . . . . . . . . . . . . . . . 43
- 4.8. Post Filtering . . . . . . . . . . . . . . . . . . . . . 43
- 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 43
- 6. Evaluation of the iLBC Implementations . . . . . . . . . . . . 43
- 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
- 7.1. Normative References . . . . . . . . . . . . . . . . . . 43
- 7.2. Informative References . . . . . . . . . . . . . . . . . 44
- 8. ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . 44
- APPENDIX A: Reference Implementation . . . . . . . . . . . . . . . 45
- A.1. iLBC_test.c. . . . . . . . . . . . . . . . . . . . . . . 46
- A.2 iLBC_encode.h. . . . . . . . . . . . . . . . . . . . . . 52
- A.3. iLBC_encode.c. . . . . . . . . . . . . . . . . . . . . . 53
- A.4. iLBC_decode.h. . . . . . . . . . . . . . . . . . . . . . 63
- A.5. iLBC_decode.c. . . . . . . . . . . . . . . . . . . . . . 64
- A.6. iLBC_define.h. . . . . . . . . . . . . . . . . . . . . . 76
- A.7. constants.h. . . . . . . . . . . . . . . . . . . . . . . 80
- A.8. constants.c. . . . . . . . . . . . . . . . . . . . . . . 82
- A.9. anaFilter.h. . . . . . . . . . . . . . . . . . . . . . . 96
- A.10. anaFilter.c. . . . . . . . . . . . . . . . . . . . . . . 97
- A.11. createCB.h . . . . . . . . . . . . . . . . . . . . . . . 98
- A.12. createCB.c . . . . . . . . . . . . . . . . . . . . . . . 99
- A.13. doCPLC.h . . . . . . . . . . . . . . . . . . . . . . . .104
- A.14. doCPLC.c . . . . . . . . . . . . . . . . . . . . . . . .104
- A.15. enhancer.h . . . . . . . . . . . . . . . . . . . . . . .109
- A.16. enhancer.c . . . . . . . . . . . . . . . . . . . . . . .110
- A.17. filter.h . . . . . . . . . . . . . . . . . . . . . . . .123
- A.18. filter.c . . . . . . . . . . . . . . . . . . . . . . . .125
- A.19. FrameClassify.h. . . . . . . . . . . . . . . . . . . . .128
- A.20. FrameClassify.c. . . . . . . . . . . . . . . . . . . . .129
- A.21. gainquant.h. . . . . . . . . . . . . . . . . . . . . . .131
- A.22. gainquant.c. . . . . . . . . . . . . . . . . . . . . . .131
- A.23. getCBvec.h . . . . . . . . . . . . . . . . . . . . . . .134
- A.24. getCBvec.c . . . . . . . . . . . . . . . . . . . . . . .134
- A.25. helpfun.h. . . . . . . . . . . . . . . . . . . . . . . .138
- A.26. helpfun.c. . . . . . . . . . . . . . . . . . . . . . . .140
- A.27. hpInput.h. . . . . . . . . . . . . . . . . . . . . . . .146
- A.28. hpInput.c. . . . . . . . . . . . . . . . . . . . . . . .146
- A.29. hpOutput.h . . . . . . . . . . . . . . . . . . . . . . .148
- A.30. hpOutput.c . . . . . . . . . . . . . . . . . . . . . . .148
- Andersen, et al. Experimental [Page 3]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.31. iCBConstruct.h . . . . . . . . . . . . . . . . . . . . .149
- A.32. iCBConstruct.c . . . . . . . . . . . . . . . . . . . . .150
- A.33. iCBSearch.h. . . . . . . . . . . . . . . . . . . . . . .152
- A.34. iCBSearch.c. . . . . . . . . . . . . . . . . . . . . . .153
- A.35. LPCdecode.h. . . . . . . . . . . . . . . . . . . . . . .163
- A.36. LPCdecode.c. . . . . . . . . . . . . . . . . . . . . . .164
- A.37. LPCencode.h. . . . . . . . . . . . . . . . . . . . . . .167
- A.38. LPCencode.c. . . . . . . . . . . . . . . . . . . . . . .167
- A.39. lsf.h. . . . . . . . . . . . . . . . . . . . . . . . . .172
- A.40. lsf.c. . . . . . . . . . . . . . . . . . . . . . . . . .172
- A.41. packing.h. . . . . . . . . . . . . . . . . . . . . . . .178
- A.42. packing.c. . . . . . . . . . . . . . . . . . . . . . . .179
- A.43. StateConstructW.h. . . . . . . . . . . . . . . . . . . .182
- A.44. StateConstructW.c. . . . . . . . . . . . . . . . . . . .183
- A.45. StateSearchW.h . . . . . . . . . . . . . . . . . . . . .185
- A.46. StateSearchW.c . . . . . . . . . . . . . . . . . . . . .186
- A.47. syntFilter.h . . . . . . . . . . . . . . . . . . . . . .190
- A.48. syntFilter.c . . . . . . . . . . . . . . . . . . . . . .190
- Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .192
- Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .194
- 1. Introduction
- This document contains the description of an algorithm for the coding
- of speech signals sampled at 8 kHz. The algorithm, called iLBC, uses
- a block-independent linear-predictive coding (LPC) algorithm and has
- support for two basic frame lengths: 20 ms at 15.2 kbit/s and 30 ms
- at 13.33 kbit/s. When the codec operates at block lengths of 20 ms,
- it produces 304 bits per block, which SHOULD be packetized as in [1].
- Similarly, for block lengths of 30 ms it produces 400 bits per block,
- which SHOULD be packetized as in [1]. The two modes for the
- different frame sizes operate in a very similar way. When they
- differ it is explicitly stated in the text, usually with the notation
- x/y, where x refers to the 20 ms mode and y refers to the 30 ms mode.
- The described algorithm results in a speech coding system with a
- controlled response to packet losses similar to what is known from
- pulse code modulation (PCM) with packet loss concealment (PLC), such
- as the ITU-T G.711 standard [4], which operates at a fixed bit rate
- of 64 kbit/s. At the same time, the described algorithm enables
- fixed bit rate coding with a quality-versus-bit rate tradeoff close
- to state-of-the-art. A suitable RTP payload format for the iLBC
- codec is specified in [1].
- Some of the applications for which this coder is suitable are real
- time communications such as telephony and videoconferencing,
- streaming audio, archival, and messaging.
- Andersen, et al. Experimental [Page 4]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Cable Television Laboratories (CableLabs(R)) has adopted iLBC as a
- mandatory PacketCable(TM) audio codec standard for VoIP over Cable
- applications [3].
- This document is organized as follows. Section 2 gives a brief
- outline of the codec. The specific encoder and decoder algorithms
- are explained in sections 3 and 4, respectively. Appendix A provides
- a c-code reference implementation.
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in BCP 14, RFC 2119 [2].
- 2. Outline of the Codec
- The codec consists of an encoder and a decoder as described in
- sections 2.1 and 2.2, respectively.
- The essence of the codec is LPC and block-based coding of the LPC
- residual signal. For each 160/240 (20 ms/30 ms) sample block, the
- following major steps are performed: A set of LPC filters are
- computed, and the speech signal is filtered through them to produce
- the residual signal. The codec uses scalar quantization of the
- dominant part, in terms of energy, of the residual signal for the
- block. The dominant state is of length 57/58 (20 ms/30 ms) samples
- and forms a start state for dynamic codebooks constructed from the
- already coded parts of the residual signal. These dynamic codebooks
- are used to code the remaining parts of the residual signal. By this
- method, coding independence between blocks is achieved, resulting in
- elimination of propagation of perceptual degradations due to packet
- loss. The method facilitates high-quality packet loss concealment
- (PLC).
- 2.1. Encoder
- The input to the encoder SHOULD be 16 bit uniform PCM sampled at 8
- kHz. It SHOULD be partitioned into blocks of BLOCKL=160/240 samples
- for the 20/30 ms frame size. Each block is divided into NSUB=4/6
- consecutive sub-blocks of SUBL=40 samples each. For 30 ms frame
- size, the encoder performs two LPC_FILTERORDER=10 linear-predictive
- coding (LPC) analyses. The first analysis applies a smooth window
- centered over the second sub-block and extending to the middle of the
- fifth sub-block. The second LPC analysis applies a smooth asymmetric
- window centered over the fifth sub-block and extending to the end of
- the sixth sub-block. For 20 ms frame size, one LPC_FILTERORDER=10
- linear-predictive coding (LPC) analysis is performed with a smooth
- window centered over the third sub-frame.
- Andersen, et al. Experimental [Page 5]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- For each of the LPC analyses, a set of line-spectral frequencies
- (LSFs) are obtained, quantized, and interpolated to obtain LSF
- coefficients for each sub-block. Subsequently, the LPC residual is
- computed by using the quantized and interpolated LPC analysis
- filters.
- The two consecutive sub-blocks of the residual exhibiting the maximal
- weighted energy are identified. Within these two sub-blocks, the
- start state (segment) is selected from two choices: the first 57/58
- samples or the last 57/58 samples of the two consecutive sub-blocks.
- The selected segment is the one of higher energy. The start state is
- encoded with scalar quantization.
- A dynamic codebook encoding procedure is used to encode 1) the 23/22
- (20 ms/30 ms) remaining samples in the two sub-blocks containing the
- start state; 2) the sub-blocks after the start state in time; and 3)
- the sub-blocks before the start state in time. Thus, the encoding
- target can be either the 23/22 samples remaining of the two sub-
- blocks containing the start state or a 40-sample sub-block. This
- target can consist of samples indexed forward in time or backward in
- time, depending on the location of the start state.
- The codebook coding is based on an adaptive codebook built from a
- codebook memory that contains decoded LPC excitation samples from the
- already encoded part of the block. These samples are indexed in the
- same time direction as the target vector, ending at the sample
- instant prior to the first sample instant represented in the target
- vector. The codebook is used in CB_NSTAGES=3 stages in a successive
- refinement approach, and the resulting three code vector gains are
- encoded with 5-, 4-, and 3-bit scalar quantization, respectively.
- The codebook search method employs noise shaping derived from the LPC
- filters, and the main decision criterion is to minimize the squared
- error between the target vector and the code vectors. Each code
- vector in this codebook comes from one of CB_EXPAND=2 codebook
- sections. The first section is filled with delayed, already encoded
- residual vectors. The code vectors of the second codebook section
- are constructed by predefined linear combinations of vectors in the
- first section of the codebook.
- As codebook encoding with squared-error matching is known to produce
- a coded signal of less power than does the scalar quantized start
- state signal, a gain re-scaling method is implemented by a refined
- search for a better set of codebook gains in terms of power matching
- after encoding. This is done by searching for a higher value of the
- gain factor for the first stage codebook, as the subsequent stage
- codebook gains are scaled by the first stage gain.
- Andersen, et al. Experimental [Page 6]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 2.2. Decoder
- Typically for packet communications, a jitter buffer placed at the
- receiving end decides whether the packet containing an encoded signal
- block has been received or lost. This logic is not part of the codec
- described here. For each encoded signal block received the decoder
- performs a decoding. For each lost signal block, the decoder
- performs a PLC operation.
- The decoding for each block starts by decoding and interpolating the
- LPC coefficients. Subsequently the start state is decoded.
- For codebook-encoded segments, each segment is decoded by
- constructing the three code vectors given by the received codebook
- indices in the same way that the code vectors were constructed in the
- encoder. The three gain factors are also decoded and the resulting
- decoded signal is given by the sum of the three codebook vectors
- scaled with respective gain.
- An enhancement algorithm is applied to the reconstructed excitation
- signal. This enhancement augments the periodicity of voiced speech
- regions. The enhancement is optimized under the constraint that the
- modification signal (defined as the difference between the enhanced
- excitation and the excitation signal prior to enhancement) has a
- short-time energy that does not exceed a preset fraction of the
- short-time energy of the excitation signal prior to enhancement.
- A packet loss concealment (PLC) operation is easily embedded in the
- decoder. The PLC operation can, e.g., be based on repeating LPC
- filters and obtaining the LPC residual signal by using a long-term
- prediction estimate from previous residual blocks.
- 3. Encoder Principles
- The following block diagram is an overview of all the components of
- the iLBC encoding procedure. The description of the blocks contains
- references to the section where that particular procedure is further
- described.
- Andersen, et al. Experimental [Page 7]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- +-----------+ +---------+ +---------+
- speech -> | 1. Pre P | -> | 2. LPC | -> | 3. Ana | ->
- +-----------+ +---------+ +---------+
- +---------------+ +--------------+
- -> | 4. Start Sel | ->| 5. Scalar Qu | ->
- +---------------+ +--------------+
- +--------------+ +---------------+
- -> |6. CB Search | -> | 7. Packetize | -> payload
- | +--------------+ | +---------------+
- ----<---------<------
- sub-frame 0..2/4 (20 ms/30 ms)
- Figure 3.1. Flow chart of the iLBC encoder
- 1. Pre-process speech with a HP filter, if needed (section 3.1).
- 2. Compute LPC parameters, quantize, and interpolate (section 3.2).
- 3. Use analysis filters on speech to compute residual (section 3.3).
- 4. Select position of 57/58-sample start state (section 3.5).
- 5. Quantize the 57/58-sample start state with scalar quantization
- (section 3.5).
- 6. Search the codebook for each sub-frame. Start with 23/22 sample
- block, then encode sub-blocks forward in time, and then encode
- sub-blocks backward in time. For each block, the steps in Figure
- 3.4 are performed (section 3.6).
- 7. Packetize the bits into the payload specified in Table 3.2.
- The input to the encoder SHOULD be 16-bit uniform PCM sampled at 8
- kHz. Also it SHOULD be partitioned into blocks of BLOCKL=160/240
- samples. Each block input to the encoder is divided into NSUB=4/6
- consecutive sub-blocks of SUBL=40 samples each.
- Andersen, et al. Experimental [Page 8]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 0 39 79 119 159
- +---------------------------------------+
- | 1 | 2 | 3 | 4 |
- +---------------------------------------+
- 20 ms frame
- 0 39 79 119 159 199 239
- +-----------------------------------------------------------+
- | 1 | 2 | 3 | 4 | 5 | 6 |
- +-----------------------------------------------------------+
- 30 ms frame
- Figure 3.2. One input block to the encoder for 20 ms (with four sub-
- frames) and 30 ms (with six sub-frames).
- 3.1. Pre-processing
- In some applications, the recorded speech signal contains DC level
- and/or 50/60 Hz noise. If these components have not been removed
- prior to the encoder call, they should be removed by a high-pass
- filter. A reference implementation of this, using a filter with a
- cutoff frequency of 90 Hz, can be found in Appendix A.28.
- 3.2. LPC Analysis and Quantization
- The input to the LPC analysis module is a possibly high-pass filtered
- speech buffer, speech_hp, that contains 240/300 (LPC_LOOKBACK +
- BLOCKL = 80/60 + 160/240 = 240/300) speech samples, where samples 0
- through 79/59 are from the previous block and samples 80/60 through
- 239/299 are from the current block. No look-ahead into the next
- block is used. For the very first block processed, the look-back
- samples are assumed to be zeros.
- For each input block, the LPC analysis calculates one/two set(s) of
- LPC_FILTERORDER=10 LPC filter coefficients using the autocorrelation
- method and the Levinson-Durbin recursion. These coefficients are
- converted to the Line Spectrum Frequency representation. In the 20
- ms case, the single lsf set represents the spectral characteristics
- as measured at the center of the third sub-block. For 30 ms frames,
- the first set, lsf1, represents the spectral properties of the input
- signal at the center of the second sub-block, and the other set,
- lsf2, represents the spectral characteristics as measured at the
- center of the fifth sub-block. The details of the computation for 30
- ms frames are described in sections 3.2.1 through 3.2.6. Section
- 3.2.7 explains how the LPC Analysis and Quantization differs for 20
- ms frames.
- Andersen, et al. Experimental [Page 9]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 3.2.1. Computation of Autocorrelation Coefficients
- The first step in the LPC analysis procedure is to calculate
- autocorrelation coefficients by using windowed speech samples. This
- windowing is the only difference in the LPC analysis procedure for
- the two sets of coefficients. For the first set, a 240-sample-long
- standard symmetric Hanning window is applied to samples 0 through 239
- of the input data. The first window, lpc_winTbl, is defined as
- lpc_winTbl[i]= 0.5 * (1.0 - cos((2*PI*(i+1))/(BLOCKL+1)));
- i=0,...,119
- lpc_winTbl[i] = winTbl[BLOCKL - i - 1]; i=120,...,239
- The windowed speech speech_hp_win1 is then obtained by multiplying
- the first 240 samples of the input speech buffer with the window
- coefficients:
- speech_hp_win1[i] = speech_hp[i] * lpc_winTbl[i];
- i=0,...,BLOCKL-1
- From these 240 windowed speech samples, 11 (LPC_FILTERORDER + 1)
- autocorrelation coefficients, acf1, are calculated:
- acf1[lag] += speech_hp_win1[n] * speech_hp_win1[n + lag];
- lag=0,...,LPC_FILTERORDER; n=0,...,BLOCKL-lag-1
- In order to make the analysis more robust against numerical precision
- problems, a spectral smoothing procedure is applied by windowing the
- autocorrelation coefficients before the LPC coefficients are
- computed. Also, a white noise floor is added to the autocorrelation
- function by multiplying coefficient zero by 1.0001 (40dB below the
- energy of the windowed speech signal). These two steps are
- implemented by multiplying the autocorrelation coefficients with the
- following window:
- lpc_lagwinTbl[0] = 1.0001;
- lpc_lagwinTbl[i] = exp(-0.5 * ((2 * PI * 60.0 * i) /FS)^2);
- i=1,...,LPC_FILTERORDER
- where FS=8000 is the sampling frequency
- Then, the windowed acf function acf1_win is obtained by
- acf1_win[i] = acf1[i] * lpc_lagwinTbl[i];
- i=0,...,LPC_FILTERORDER
- The second set of autocorrelation coefficients, acf2_win, are
- obtained in a similar manner. The window, lpc_asymwinTbl, is applied
- to samples 60 through 299, i.e., the entire current block. The
- Andersen, et al. Experimental [Page 10]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- window consists of two segments, the first (samples 0 to 219) being
- half a Hanning window with length 440 and the second a quarter of a
- cycle of a cosine wave. By using this asymmetric window, an LPC
- analysis centered in the fifth sub-block is obtained without the need
- for any look-ahead, which would add delay. The asymmetric window is
- defined as
- lpc_asymwinTbl[i] = (sin(PI * (i + 1) / 441))^2; i=0,...,219
- lpc_asymwinTbl[i] = cos((i - 220) * PI / 40); i=220,...,239
- and the windowed speech is computed by
- speech_hp_win2[i] = speech_hp[i + LPC_LOOKBACK] *
- lpc_asymwinTbl[i]; i=0,....BLOCKL-1
- The windowed autocorrelation coefficients are then obtained in
- exactly the same way as for the first analysis instance.
- The generation of the windows lpc_winTbl, lpc_asymwinTbl, and
- lpc_lagwinTbl are typically done in advance, and the arrays are
- stored in ROM rather than repeating the calculation for every block.
- 3.2.2. Computation of LPC Coefficients
- From the 2 x 11 smoothed autocorrelation coefficients, acf1_win and
- acf2_win, the 2 x 11 LPC coefficients, lp1 and lp2, are calculated
- in the same way for both analysis locations by using the well known
- Levinson-Durbin recursion. The first LPC coefficient is always 1.0,
- resulting in ten unique coefficients.
- After determining the LPC coefficients, a bandwidth expansion
- procedure is applied to smooth the spectral peaks in the
- short-term spectrum. The bandwidth addition is obtained by the
- following modification of the LPC coefficients:
- lp1_bw[i] = lp1[i] * chirp^i; i=0,...,LPC_FILTERORDER
- lp2_bw[i] = lp2[i] * chirp^i; i=0,...,LPC_FILTERORDER
- where "chirp" is a real number between 0 and 1. It is RECOMMENDED to
- use a value of 0.9.
- 3.2.3. Computation of LSF Coefficients from LPC Coefficients
- Thus far, two sets of LPC coefficients that represent the short-term
- spectral characteristics of the speech signal for two different time
- locations within the current block have been determined. These
- coefficients SHOULD be quantized and interpolated. Before this is
- Andersen, et al. Experimental [Page 11]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- done, it is advantageous to convert the LPC parameters into another
- type of representation called Line Spectral Frequencies (LSF). The
- LSF parameters are used because they are better suited for
- quantization and interpolation than the regular LPC coefficients.
- Many computationally efficient methods for calculating the LSFs from
- the LPC coefficients have been proposed in the literature. The
- detailed implementation of one applicable method can be found in
- Appendix A.26. The two arrays of LSF coefficients obtained, lsf1 and
- lsf2, are of dimension 10 (LPC_FILTERORDER).
- 3.2.4. Quantization of LSF Coefficients
- Because the LPC filters defined by the two sets of LSFs are also
- needed in the decoder, the LSF parameters need to be quantized and
- transmitted as side information. The total number of bits required
- to represent the quantization of the two LSF representations for one
- block of speech is 40, with 20 bits used for each of lsf1 and lsf2.
- For computational and storage reasons, the LSF vectors are quantized
- using three-split vector quantization (VQ). That is, the LSF vectors
- are split into three sub-vectors that are each quantized with a
- regular VQ. The quantized versions of lsf1 and lsf2, qlsf1 and
- qlsf2, are obtained by using the same memoryless split VQ. The
- length of each of these two LSF vectors is 10, and they are split
- into three sub-vectors containing 3, 3, and 4 values, respectively.
- For each of the sub-vectors, a separate codebook of quantized values
- has been designed with a standard VQ training method for a large
- database containing speech from a large number of speakers recorded
- under various conditions. The size of each of the three codebooks
- associated with the split definitions above is
- int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128};
- The actual values of the vector quantization codebook that must be
- used can be found in the reference code of Appendix A. Both sets of
- LSF coefficients, lsf1 and lsf2, are quantized with a standard
- memoryless split vector quantization (VQ) structure using the squared
- error criterion in the LSF domain. The split VQ quantization
- consists of the following steps:
- 1) Quantize the first three LSF coefficients (1 - 3) with a VQ
- codebook of size 64.
- 2) Quantize the next three LSF coefficients 4 - 6 with VQ a codebook
- of size 128.
- 3) Quantize the last four LSF coefficients (7 - 10) with a VQ
- codebook of size 128.
- Andersen, et al. Experimental [Page 12]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- This procedure, repeated for lsf1 and lsf2, gives six quantization
- indices and the quantized sets of LSF coefficients qlsf1 and qlsf2.
- Each set of three indices is encoded with 6 + 7 + 7 = 20 bits. The
- total number of bits used for LSF quantization in a block is thus 40
- bits.
- 3.2.5. Stability Check of LSF Coefficients
- The LSF representation of the LPC filter has the convenient property
- that the coefficients are ordered by increasing value, i.e., lsf(n-1)
- < lsf(n), 0 < n < 10, if the corresponding synthesis filter is
- stable. As we are employing a split VQ scheme, it is possible that
- at the split boundaries the LSF coefficients are not ordered
- correctly and hence that the corresponding LP filter is unstable. To
- ensure that the filter used is stable, a stability check is performed
- for the quantized LSF vectors. If it turns out that the coefficients
- are not ordered appropriately (with a safety margin of 50 Hz to
- ensure that formant peaks are not too narrow), they will be moved
- apart. The detailed method for this can be found in Appendix A.40.
- The same procedure is performed in the decoder. This ensures that
- exactly the same LSF representations are used in both encoder and
- decoder.
- 3.2.6. Interpolation of LSF Coefficients
- From the two sets of LSF coefficients that are computed for each
- block of speech, different LSFs are obtained for each sub-block by
- means of interpolation. This procedure is performed for the original
- LSFs (lsf1 and lsf2), as well as the quantized versions qlsf1 and
- qlsf2, as both versions are used in the encoder. Here follows a
- brief summary of the interpolation scheme; the details are found in
- the c-code of Appendix A. In the first sub-block, the average of the
- second LSF vector from the previous block and the first LSF vector in
- the current block is used. For sub-blocks two through five, the LSFs
- used are obtained by linear interpolation from lsf1 (and qlsf1) to
- lsf2 (and qlsf2), with lsf1 used in sub-block two and lsf2 in sub-
- block five. In the last sub-block, lsf2 is used. For the very first
- block it is assumed that the last LSF vector of the previous block is
- equal to a predefined vector, lsfmeanTbl, obtained by calculating the
- mean LSF vector of the LSF design database.
- lsfmeanTbl[LPC_FILTERORDER] = {0.281738, 0.445801, 0.663330,
- 0.962524, 1.251831, 1.533081, 1.850586, 2.137817,
- 2.481445, 2.777344}
- Andersen, et al. Experimental [Page 13]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- The interpolation method is standard linear interpolation in the LSF
- domain. The interpolated LSF values are converted to LPC
- coefficients for each sub-block. The unquantized and quantized LPC
- coefficients form two sets of filters respectively. The unquantized
- analysis filter for sub-block k is defined as follows
- ___
- \
- Ak(z)= 1 + > ak(i)*z^(-i)
- /__
- i=1...LPC_FILTERORDER
- The quantized analysis filter for sub-block k is defined as follows
- ___
- \
- A~k(z)= 1 + > a~k(i)*z^(-i)
- /__
- i=1...LPC_FILTERORDER
- A reference implementation of the lsf encoding is given in Appendix
- A.38. A reference implementation of the corresponding decoding can
- be found in Appendix A.36.
- 3.2.7. LPC Analysis and Quantization for 20 ms Frames
- As previously stated, the codec only calculates one set of LPC
- parameters for the 20 ms frame size as opposed to two sets for 30 ms
- frames. A single set of autocorrelation coefficients is calculated
- on the LPC_LOOKBACK + BLOCKL = 80 + 160 = 240 samples. These samples
- are windowed with the asymmetric window lpc_asymwinTbl, centered over
- the third sub-frame, to form speech_hp_win. Autocorrelation
- coefficients, acf, are calculated on the 240 samples in speech_hp_win
- and then windowed exactly as in section 3.2.1 (resulting in
- acf_win).
- This single set of windowed autocorrelation coefficients is used to
- calculate LPC coefficients, LSF coefficients, and quantized LSF
- coefficients in exactly the same manner as in sections 3.2.3 through
- 3.2.4. As for the 30 ms frame size, the ten LSF coefficients are
- divided into three sub-vectors of size 3, 3, and 4 and quantized by
- using the same scheme and codebook as in section 3.2.4 to finally get
- 3 quantization indices. The quantized LSF coefficients are
- stabilized with the algorithm described in section 3.2.5.
- From the set of LSF coefficients computed for this block and those
- from the previous block, different LSFs are obtained for each sub-
- block by means of interpolation. The interpolation is done linearly
- in the LSF domain over the four sub-blocks, so that the n-th sub-
- Andersen, et al. Experimental [Page 14]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- frame uses the weight (4-n)/4 for the LSF from old frame and the
- weight n/4 of the LSF from the current frame. For the very first
- block the mean LSF, lsfmeanTbl, is used as the LSF from the previous
- block. Similarly as seen in section 3.2.6, both unquantized, A(z),
- and quantized, A~(z), analysis filters are calculated for each of the
- four sub-blocks.
- 3.3. Calculation of the Residual
- The block of speech samples is filtered by the quantized and
- interpolated LPC analysis filters to yield the residual signal. In
- particular, the corresponding LPC analysis filter for each 40 sample
- sub-block is used to filter the speech samples for the same sub-
- block. The filter memory at the end of each sub-block is carried
- over to the LPC filter of the next sub-block. The signal at the
- output of each LP analysis filter constitutes the residual signal for
- the corresponding sub-block.
- A reference implementation of the LPC analysis filters is given in
- Appendix A.10.
- 3.4. Perceptual Weighting Filter
- In principle any good design of a perceptual weighting filter can be
- applied in the encoder without compromising this codec definition.
- However, it is RECOMMENDED to use the perceptual weighting filter Wk
- for sub-block k specified below:
- Wk(z)=1/Ak(z/LPC_CHIRP_WEIGHTDENUM), where
- LPC_CHIRP_WEIGHTDENUM = 0.4222
- This is a simple design with low complexity that is applied in the
- LPC residual domain. Here Ak(z) is the filter obtained for sub-block
- k from unquantized but interpolated LSF coefficients.
- 3.5. Start State Encoder
- The start state is quantized by using a common 6-bit scalar quantizer
- for the block and a 3-bit scalar quantizer operating on scaled
- samples in the weighted speech domain. In the following we describe
- the state encoding in greater detail.
- Andersen, et al. Experimental [Page 15]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 3.5.1. Start State Estimation
- The two sub-blocks containing the start state are determined by
- finding the two consecutive sub-blocks in the block having the
- highest power. Advantageously, down-weighting is used in the
- beginning and end of the sub-frames, i.e., the following measure is
- computed (NSUB=4/6 for 20/30 ms frame size):
- nsub=1,...,NSUB-1
- ssqn[nsub] = 0.0;
- for (i=(nsub-1)*SUBL; i<(nsub-1)*SUBL+5; i++)
- ssqn[nsub] += sampEn_win[i-(nsub-1)*SUBL]*
- residual[i]*residual[i];
- for (i=(nsub-1)*SUBL+5; i<(nsub+1)*SUBL-5; i++)
- ssqn[nsub] += residual[i]*residual[i];
- for (i=(nsub+1)*SUBL-5; i<(nsub+1)*SUBL; i++)
- ssqn[nsub] += sampEn_win[(nsub+1)*SUBL-i-1]*
- residual[i]*residual[i];
- where sampEn_win[5]={1/6, 2/6, 3/6, 4/6, 5/6}; MAY be used. The
- sub-frame number corresponding to the maximum value of
- ssqEn_win[nsub-1]*ssqn[nsub] is selected as the start state
- indicator. A weighting of ssqEn_win[]={0.8,0.9,1.0,0.9,0.8} for 30
- ms frames and ssqEn_win[]={0.9,1.0,0.9} for 20 ms frames; MAY
- advantageously be used to bias the start state towards the middle of
- the frame.
- For 20 ms frames there are three possible positions for the two-sub-
- block length maximum power segment; the start state position is
- encoded with 2 bits. The start state position, start, MUST be
- encoded as
- start=1: start state in sub-frame 0 and 1
- start=2: start state in sub-frame 1 and 2
- start=3: start state in sub-frame 2 and 3
- For 30 ms frames there are five possible positions of the two-sub-
- block length maximum power segment, the start state position is
- encoded with 3 bits. The start state position, start, MUST be
- encoded as
- start=1: start state in sub-frame 0 and 1
- start=2: start state in sub-frame 1 and 2
- start=3: start state in sub-frame 2 and 3
- start=4: start state in sub-frame 3 and 4
- start=5: start state in sub-frame 4 and 5
- Andersen, et al. Experimental [Page 16]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Hence, in both cases, index 0 is not used. In order to shorten the
- start state for bit rate efficiency, the start state is brought down
- to STATE_SHORT_LEN=57 samples for 20 ms frames and STATE_SHORT_LEN=58
- samples for 30 ms frames. The power of the first 23/22 and last
- 23/22 samples of the two sub-frame blocks identified above is
- computed as the sum of the squared signal sample values, and the
- 23/22-sample segment with the lowest power is excluded from the start
- state. One bit is transmitted to indicate which of the two possible
- 57/58 sample segments is used. The start state position within the
- two sub-frames determined above, state_first, MUST be encoded as
- state_first=1: start state is first STATE_SHORT_LEN samples
- state_first=0: start state is last STATE_SHORT_LEN samples
- 3.5.2. All-Pass Filtering and Scale Quantization
- The block of residual samples in the start state is first filtered by
- an all-pass filter with the quantized LPC coefficients as denominator
- and reversed quantized LPC coefficients as numerator. The purpose of
- this phase-dispersion filter is to get a more even distribution of
- the sample values in the residual signal. The filtering is performed
- by circular convolution, where the initial filter memory is set to
- zero.
- res(0..(STATE_SHORT_LEN-1)) = uncoded start state residual
- res((STATE_SHORT_LEN)..(2*STATE_SHORT_LEN-1)) = 0
- Pk(z) = A~rk(z)/A~k(z), where
- ___
- \
- A~rk(z)= z^(-LPC_FILTERORDER)+>a~k(i+1)*z^(i-(LPC_FILTERORDER-1))
- /__
- i=0...(LPC_FILTERORDER-1)
- and A~k(z) is taken from the block where the start state begins
- res -> Pk(z) -> filtered
- ccres(k) = filtered(k) + filtered(k+STATE_SHORT_LEN),
- k=0..(STATE_SHORT_LEN-1)
- The all-pass filtered block is searched for its largest magnitude
- sample. The 10-logarithm of this magnitude is quantized with a 6-bit
- quantizer, state_frgqTbl, by finding the nearest representation.
- Andersen, et al. Experimental [Page 17]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- This results in an index, idxForMax, corresponding to a quantized
- value, qmax. The all-pass filtered residual samples in the block are
- then multiplied with a scaling factor scal=4.5/(10^qmax) to yield
- normalized samples.
- state_frgqTbl[64] = {1.000085, 1.071695, 1.140395, 1.206868,
- 1.277188, 1.351503, 1.429380, 1.500727, 1.569049,
- 1.639599, 1.707071, 1.781531, 1.840799, 1.901550,
- 1.956695, 2.006750, 2.055474, 2.102787, 2.142819,
- 2.183592, 2.217962, 2.257177, 2.295739, 2.332967,
- 2.369248, 2.402792, 2.435080, 2.468598, 2.503394,
- 2.539284, 2.572944, 2.605036, 2.636331, 2.668939,
- 2.698780, 2.729101, 2.759786, 2.789834, 2.818679,
- 2.848074, 2.877470, 2.906899, 2.936655, 2.967804,
- 3.000115, 3.033367, 3.066355, 3.104231, 3.141499,
- 3.183012, 3.222952, 3.265433, 3.308441, 3.350823,
- 3.395275, 3.442793, 3.490801, 3.542514, 3.604064,
- 3.666050, 3.740994, 3.830749, 3.938770, 4.101764}
- 3.5.3. Scalar Quantization
- The normalized samples are quantized in the perceptually weighted
- speech domain by a sample-by-sample scalar DPCM quantization as
- depicted in Figure 3.3. Each sample in the block is filtered by a
- weighting filter Wk(z), specified in section 3.4, to form a weighted
- speech sample x[n]. The target sample d[n] is formed by subtracting
- a predicted sample y[n], where the prediction filter is given by
- Pk(z) = 1 - 1 / Wk(z).
- +-------+ x[n] + d[n] +-----------+ u[n]
- residual -->| Wk(z) |-------->(+)---->| Quantizer |------> quantized
- +-------+ - /|\ +-----------+ | residual
- | \|/
- y[n] +--------------------->(+)
- | |
- | +------+ |
- +--------| Pk(z)|<------+
- +------+
- Figure 3.3. Quantization of start state samples by DPCM in weighted
- speech domain.
- The coded state sample u[n] is obtained by quantizing d[n] with a 3-
- bit quantizer with quantization table state_sq3Tbl.
- state_sq3Tbl[8] = {-3.719849, -2.177490, -1.130005, -0.309692,
- 0.444214, 1.329712, 2.436279, 3.983887}
- Andersen, et al. Experimental [Page 18]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- The quantized samples are transformed back to the residual domain by
- 1) scaling with 1/scal; 2) time-reversing the scaled samples; 3)
- filtering the time-reversed samples by the same all-pass filter, as
- in section 3.5.2, by using circular convolution; and 4) time-
- reversing the filtered samples. (More detail is in section 4.2.)
- A reference implementation of the start-state encoding can be found
- in Appendix A.46.
- 3.6. Encoding the Remaining Samples
- A dynamic codebook is used to encode 1) the 23/22 remaining samples
- in the two sub-blocks containing the start state; 2) the sub-blocks
- after the start state in time; and 3) the sub-blocks before the start
- state in time. Thus, the encoding target can be either the 23/22
- samples remaining of the 2 sub-blocks containing the start state, or
- a 40-sample sub-block. This target can consist of samples that are
- indexed forward in time or backward in time, depending on the
- location of the start state. The length of the target is denoted by
- lTarget.
- The coding is based on an adaptive codebook that is built from a
- codebook memory that contains decoded LPC excitation samples from the
- already encoded part of the block. These samples are indexed in the
- same time direction as is the target vector and end at the sample
- instant prior to the first sample instant represented in the target
- vector. The codebook memory has length lMem, which is equal to
- CB_MEML=147 for the two/four 40-sample sub-blocks and 85 for the
- 23/22-sample sub-block.
- The following figure shows an overview of the encoding procedure.
- +------------+ +---------------+ +-------------+
- -> | 1. Decode | -> | 2. Mem setup | -> | 3. Perc. W. | ->
- +------------+ +---------------+ +-------------+
- +------------+ +-----------------+
- -> | 4. Search | -> | 5. Upd. Target | ------------------>
- | +------------+ +------------------ |
- ----<-------------<-----------<----------
- stage=0..2
- +----------------+
- -> | 6. Recalc G[0] | ---------------> gains and CB indices
- +----------------+
- Figure 3.4. Flow chart of the codebook search in the iLBC encoder.
- Andersen, et al. Experimental [Page 19]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 1. Decode the part of the residual that has been encoded so far,
- using the codebook without perceptual weighting.
- 2. Set up the memory by taking data from the decoded residual. This
- memory is used to construct codebooks. For blocks preceding the
- start state, both the decoded residual and the target are time
- reversed (section 3.6.1).
- 3. Filter the memory + target with the perceptual weighting filter
- (section 3.6.2).
- 4. Search for the best match between the target and the codebook
- vector. Compute the optimal gain for this match and quantize that
- gain (section 3.6.4).
- 5. Update the perceptually weighted target by subtracting the
- contribution from the selected codebook vector from the
- perceptually weighted memory (quantized gain times selected
- vector). Repeat 4 and 5 for the two additional stages.
- 6. Calculate the energy loss due to encoding of the residual. If
- needed, compensate for this loss by an upscaling and
- requantization of the gain for the first stage (section 3.7).
- The following sections provide an in-depth description of the
- different blocks of Figure 3.4.
- 3.6.1. Codebook Memory
- The codebook memory is based on the already encoded sub-blocks, so
- the available data for encoding increases for each new sub-block that
- has been encoded. Until enough sub-blocks have been encoded to fill
- the codebook memory with data, it is padded with zeros. The
- following figure shows an example of the order in which the sub-
- blocks are encoded for the 30 ms frame size if the start state is
- located in the last 58 samples of sub-block 2 and 3.
- +-----------------------------------------------------+
- | 5 | 1 |///|////////| 2 | 3 | 4 |
- +-----------------------------------------------------+
- Figure 3.5. The order from 1 to 5 in which the sub-blocks are
- encoded. The slashed area is the start state.
- Andersen, et al. Experimental [Page 20]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- The first target sub-block to be encoded is number 1, and the
- corresponding codebook memory is shown in the following figure. As
- the target vector comes before the start state in time, the codebook
- memory and target vector are time reversed; thus, after the block has
- been time reversed the search algorithm can be reused. As only the
- start state has been encoded so far, the last samples of the codebook
- memory are padded with zeros.
- +-------------------------
- |zeros|\\\\\\\\|\\\\| 1 |
- +-------------------------
- Figure 3.6. The codebook memory, length lMem=85 samples, and the
- target vector 1, length 22 samples.
- The next step is to encode sub-block 2 by using the memory that now
- has increased since sub-block 1 has been encoded. The following
- figure shows the codebook memory for encoding of sub-block 2.
- +-----------------------------------
- | zeros | 1 |///|////////| 2 |
- +-----------------------------------
- Figure 3.7. The codebook memory, length lMem=147 samples, and the
- target vector 2, length 40 samples.
- The next step is to encode sub-block 3 by using the memory which has
- been increased yet again since sub-blocks 1 and 2 have been encoded,
- but the sub-block still has to be padded with a few zeros. The
- following figure shows the codebook memory for encoding of sub-block
- 3.
- +------------------------------------------
- |zeros| 1 |///|////////| 2 | 3 |
- +------------------------------------------
- Figure 3.8. The codebook memory, length lMem=147 samples, and the
- target vector 3, length 40 samples.
- The next step is to encode sub-block 4 by using the memory which now
- has increased yet again since sub-blocks 1, 2, and 3 have been
- encoded. This time, the memory does not have to be padded with
- zeros. The following figure shows the codebook memory for encoding
- of sub-block 4.
- Andersen, et al. Experimental [Page 21]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- +------------------------------------------
- |1|///|////////| 2 | 3 | 4 |
- +------------------------------------------
- Figure 3.9. The codebook memory, length lMem=147 samples, and the
- target vector 4, length 40 samples.
- The final target sub-block to be encoded is number 5, and the
- following figure shows the corresponding codebook memory. As the
- target vector comes before the start state in time, the codebook
- memory and target vector are time reversed.
- +-------------------------------------------
- | 3 | 2 |\\\\\\\\|\\\\| 1 | 5 |
- +-------------------------------------------
- Figure 3.10. The codebook memory, length lMem=147 samples, and the
- target vector 5, length 40 samples.
- For the case of 20 ms frames, the encoding procedure looks almost
- exactly the same. The only difference is that the size of the start
- state is 57 samples and that there are only three sub-blocks to be
- encoded. The encoding order is the same as above, starting with the
- 23-sample target and then encoding the two remaining 40-sample sub-
- blocks, first going forward in time and then going backward in time
- relative to the start state.
- 3.6.2. Perceptual Weighting of Codebook Memory and Target
- To provide a perceptual weighting of the coding error, a
- concatenation of the codebook memory and the target to be coded is
- all-pole filtered with the perceptual weighting filter specified in
- section 3.4. The filter state of the weighting filter is set to
- zero.
- in(0..(lMem-1)) = unweighted codebook memory
- in(lMem..(lMem+lTarget-1)) = unweighted target signal
- in -> Wk(z) -> filtered,
- where Wk(z) is taken from the sub-block of the target
- weighted codebook memory = filtered(0..(lMem-1))
- weighted target signal = filtered(lMem..(lMem+lTarget-1))
- The codebook search is done with the weighted codebook memory and the
- weighted target, whereas the decoding and the codebook memory update
- uses the unweighted codebook memory.
- Andersen, et al. Experimental [Page 22]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 3.6.3. Codebook Creation
- The codebook for the search is created from the perceptually weighted
- codebook memory. It consists of two sections, where the first is
- referred to as the base codebook and the second as the expanded
- codebook, as it is created by linear combinations of the first. Each
- of these two sections also has a subsection referred to as the
- augmented codebook. The augmented codebook is only created and used
- for the coding of the 40-sample sub-blocks and not for the 23/22-
- sample sub-block case. The codebook size used for the different
- sub-blocks and different stages are summarized in the table below.
- Stage
- 1 2 & 3
- --------------------------------------------
- 22 128 (64+0)*2 128 (64+0)*2
- Sub- 1:st 40 256 (108+20)*2 128 (44+20)*2
- Blocks 2:nd 40 256 (108+20)*2 256 (108+20)*2
- 3:rd 40 256 (108+20)*2 256 (108+20)*2
- 4:th 40 256 (108+20)*2 256 (108+20)*2
- Table 3.1. Codebook sizes for the 30 ms mode.
- Table 3.1 shows the codebook size for the different sub-blocks and
- stages for 30 ms frames. Inside the parentheses it shows how the
- number of codebook vectors is distributed, within the two sections,
- between the base/expanded codebook and the augmented base/expanded
- codebook. It should be interpreted in the following way:
- (base/expanded cb + augmented base/expanded cb). The total number of
- codebook vectors for a specific sub-block and stage is given by the
- following formula:
- Tot. cb vectors = base cb + aug. base cb + exp. cb + aug. exp. cb
- The corresponding values to Figure 3.1 for 20 ms frames are only
- slightly modified. The short sub-block is 23 instead of 22 samples,
- and the 3:rd and 4:th sub-frame are not present.
- 3.6.3.1. Creation of a Base Codebook
- The base codebook is given by the perceptually weighted codebook
- memory that is mentioned in section 3.5.3. The different codebook
- vectors are given by sliding a window of length 23/22 or 40, given by
- variable lTarget, over the lMem-long perceptually weighted codebook
- memory. The indices are ordered so that the codebook vector
- containing sample (lMem-lTarget-n) to (lMem-n-1) of the codebook
- Andersen, et al. Experimental [Page 23]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- memory vector has index n, where n=0..lMem-lTarget. Thus the total
- number of base codebook vectors is lMem-lTarget+1, and the indices
- are ordered from sample delay lTarget (23/22 or 40) to lMem+1 (86 or
- 148).
- 3.6.3.2. Codebook Expansion
- The base codebook is expanded by a factor of 2, creating an
- additional section in the codebook. This new section is obtained by
- filtering the base codebook, base_cb, with a FIR filter with filter
- length CB_FILTERLEN=8. The construction of the expanded codebook
- compensates for the delay of four samples introduced by the FIR
- filter.
- cbfiltersTbl[CB_FILTERLEN]={-0.033691, 0.083740, -0.144043,
- 0.713379, 0.806152, -0.184326,
- 0.108887, -0.034180};
- ___
- \
- exp_cb(k)= + > cbfiltersTbl(i)*x(k-i+4)
- /__
- i=0...(LPC_FILTERORDER-1)
- where x(j) = base_cb(j) for j=0..lMem-1 and 0 otherwise
- The individual codebook vectors of the new filtered codebook, exp_cb,
- and their indices are obtained in the same fashion as described above
- for the base codebook.
- 3.6.3.3. Codebook Augmentation
- For cases where encoding entire sub-blocks, i.e., cbveclen=40, the
- base and expanded codebooks are augmented to increase codebook
- richness. The codebooks are augmented by vectors produced by
- interpolation of segments. The base and expanded codebook,
- constructed above, consists of vectors corresponding to sample delays
- in the range from cbveclen to lMem. The codebook augmentation
- attempts to augment these codebooks with vectors corresponding to
- sample delays from 20 to 39. However, not all of these samples are
- present in the base codebook and expanded codebook, respectively.
- Therefore, the augmentation vectors are constructed as linear
- combinations between samples corresponding to sample delays in the
- range 20 to 39. The general idea of this procedure is presented in
- the following figures and text. The procedure is performed for both
- the base codebook and the expanded codebook.
- Andersen, et al. Experimental [Page 24]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- - - ------------------------|
- codebook memory |
- - - ------------------------|
- |-5-|---15---|-5-|
- pi pp po
- | | Codebook vector
- |---15---|-5-|-----20-----| <- corresponding to
- i ii iii sample delay 20
- Figure 3.11. Generation of the first augmented codebook.
- Figure 3.11 shows the codebook memory with pointers pi, pp, and po,
- where pi points to sample 25, pp to sample 20, and po to sample 5.
- Below the codebook memory, the augmented codebook vector
- corresponding to sample delay 20 is drawn. Segment i consists of
- fifteen samples from pointer pp and forward in time. Segment ii
- consists of five interpolated samples from pi and forward and from po
- and forward. The samples are linearly interpolated with weights
- [0.0, 0.2, 0.4, 0.6, 0.8] for pi and weights [1.0, 0.8, 0.6, 0.4,
- 0.2] for po. Segment iii consists of twenty samples from pp and
- forward. The augmented codebook vector corresponding to sample delay
- 21 is produced by moving pointers pp and pi one sample backward in
- time. This gives us the following figure.
- - - ------------------------|
- codebook memory |
- - - ------------------------|
- |-5-|---16---|-5-|
- pi pp po
- | | Codebook vector
- |---16---|-5-|-----19-----| <- corresponding to
- i ii iii sample delay 21
- Figure 3.12. Generation of the second augmented codebook.
- Figure 3.12 shows the codebook memory with pointers pi, pp and po
- where pi points to sample 26, pp to sample 21, and po to sample 5.
- Below the codebook memory, the augmented codebook vector
- corresponding to sample delay 21 is drawn. Segment i now consists of
- sixteen samples from pp and forward. Segment ii consists of five
- interpolated samples from pi and forward and from po and forward, and
- the interpolation weights are the same throughout the procedure.
- Segment iii consists of nineteen samples from pp and forward. The
- same procedure of moving the two pointers is continued until the last
- augmented vector corresponding to sample delay 39 has been created.
- This gives a total of twenty new codebook vectors to each of the two
- Andersen, et al. Experimental [Page 25]
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- sections. Thus the total number of codebook vectors for each of the
- two sections, when including the augmented codebook, becomes lMem-
- SUBL+1+SUBL/2. This is provided that augmentation is evoked, i.e.,
- that lTarget=SUBL.
- 3.6.4. Codebook Search
- The codebook search uses the codebooks described in the sections
- above to find the best match of the perceptually weighted target, see
- section 3.6.2. The search method is a multi-stage gain-shape
- matching performed as follows. At each stage the best shape vector
- is identified, then the gain is calculated and quantized, and finally
- the target is updated in preparation for the next codebook search
- stage. The number of stages is CB_NSTAGES=3.
- If the target is the 23/22-sample vector the codebooks are indexed so
- that the base codebook is followed by the expanded codebook. If the
- target is 40 samples the order is as follows: base codebook,
- augmented base codebook, expanded codebook, and augmented expanded
- codebook. The size of each codebook section and its corresponding
- augmented section is given by Table 3.1 in section 3.6.3.
- For example, when the second 40-sample sub-block is coded, indices 0
- - 107 correspond to the base codebook, 108 - 127 correspond to the
- augmented base codebook, 128 - 235 correspond to the expanded
- codebook, and indices 236 - 255 correspond to the augmented expanded
- codebook. The indices are divided in the same fashion for all stages
- in the example. Only in the case of coding the first 40-sample sub-
- block is there a difference between stages (see Table 3.1).
- 3.6.4.1. Codebook Search at Each Stage
- The codebooks are searched to find the best match to the target at
- each stage. When the best match is found, the target is updated and
- the next-stage search is started. The three chosen codebook vectors
- and their corresponding gains constitute the encoded sub-block. The
- best match is decided by the following three criteria:
- 1. Compute the measure
- (target*cbvec)^2 / ||cbvec||^2
- for all codebook vectors, cbvec, and choose the codebook vector
- maximizing the measure. The expression (target*cbvec) is the dot
- product between the target vector to be coded and the codebook vector
- for which we compute the measure. The norm, ||x||, is defined as the
- square root of (x*x).
- Andersen, et al. Experimental [Page 26]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 2. The absolute value of the gain, corresponding to the chosen
- codebook vector, cbvec, must be smaller than a fixed limit,
- CB_MAXGAIN=1.3:
- |gain| < CB_MAXGAIN
- where the gain is computed in the following way:
- gain = (target*cbvec) / ||cbvec||^2
- 3. For the first stage, the dot product of the chosen codebook vector
- and target must be positive:
- target*cbvec > 0
- In practice the above criteria are used in a sequential search
- through all codebook vectors. The best match is found by registering
- a new max measure and index whenever the previously registered max
- measure is surpassed and all other criteria are fulfilled. If none
- of the codebook vectors fulfill (2) and (3), the first codebook
- vector is selected.
- 3.6.4.2. Gain Quantization at Each Stage
- The gain follows as a result of the computation
- gain = (target*cbvec) / ||cbvec||^2
- for the optimal codebook vector found by the procedure in section
- 3.6.4.1.
- The three stages quantize the gain, using 5, 4, and 3 bits,
- respectively. In the first stage, the gain is limited to positive
- values. This gain is quantized by finding the nearest value in the
- quantization table gain_sq5Tbl.
- gain_sq5Tbl[32]={0.037476, 0.075012, 0.112488, 0.150024, 0.187500,
- 0.224976, 0.262512, 0.299988, 0.337524, 0.375000,
- 0.412476, 0.450012, 0.487488, 0.525024, 0.562500,
- 0.599976, 0.637512, 0.674988, 0.712524, 0.750000,
- 0.787476, 0.825012, 0.862488, 0.900024, 0.937500,
- 0.974976, 1.012512, 1.049988, 1.087524, 1.125000,
- 1.162476, 1.200012}
- The gains of the subsequent two stages can be either positive or
- negative. The gains are quantized by using a quantization table
- times a scale factor. The second stage uses the table gain_sq4Tbl,
- and the third stage uses gain_sq3Tbl. The scale factor equates 0.1
- Andersen, et al. Experimental [Page 27]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- or the absolute value of the quantized gain representation value
- obtained in the previous stage, whichever is larger. Again, the
- resulting gain index is the index to the nearest value of the
- quantization table times the scale factor.
- gainQ = scaleFact * gain_sqXTbl[index]
- gain_sq4Tbl[16]={-1.049988, -0.900024, -0.750000, -0.599976,
- -0.450012, -0.299988, -0.150024, 0.000000, 0.150024,
- 0.299988, 0.450012, 0.599976, 0.750000, 0.900024,
- 1.049988, 1.200012}
- gain_sq3Tbl[8]={-1.000000, -0.659973, -0.330017,0.000000,
- 0.250000, 0.500000, 0.750000, 1.00000}
- 3.6.4.3. Preparation of Target for Next Stage
- Before performing the search for the next stage, the perceptually
- weighted target vector is updated by subtracting from it the selected
- codebook vector (from the perceptually weighted codebook) times the
- corresponding quantized gain.
- target[i] = target[i] - gainQ * selected_vec[i];
- A reference implementation of the codebook encoding is found in
- Appendix A.34.
- 3.7. Gain Correction Encoding
- The start state is quantized in a relatively model independent manner
- using 3 bits per sample. In contrast, the remaining parts of the
- block are encoded by using an adaptive codebook. This codebook will
- produce high matching accuracy whenever there is a high correlation
- between the target and the best codebook vector. For unvoiced speech
- segments and background noises, this is not necessarily so, which,
- due to the nature of the squared error criterion, results in a coded
- signal with less power than the target signal. As the coded start
- state has good power matching to the target, the result is a power
- fluctuation within the encoded frame. Perceptually, the main problem
- with this is that the time envelope of the signal energy becomes
- unsteady. To overcome this problem, the gains for the codebooks are
- re-scaled after the codebook encoding by searching for a new gain
- factor for the first stage codebook that provides better power
- matching.
- First, the energy for the target signal, tene, is computed along with
- the energy for the coded signal, cene, given by the addition of the
- three gain scaled codebook vectors. Because the gains of the second
- Andersen, et al. Experimental [Page 28]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- and third stage scale with the gain of the first stage, when the
- first stage gain is changed from gain[0] to gain_sq5Tbl[i] the energy
- of the coded signal changes from cene to
- cene*(gain_sq5Tbl[i]*gain_sq5Tbl[i])/(gain[0]*gain[0])
- where gain[0] is the gain for the first stage found in the original
- codebook search. A refined search is performed by testing the gain
- indices i=0 to 31, and as long as the new codebook energy as given
- above is less than tene, the gain index for stage 1 is increased. A
- restriction is applied so that the new gain value for stage 1 cannot
- be more than two times higher than the original value found in the
- codebook search. Note that by using this method we do not change the
- shape of the encoded vector, only the gain or amplitude.
- 3.8. Bitstream Definition
- The total number of bits used to describe one frame of 20 ms speech
- is 304, which fits in 38 bytes and results in a bit rate of 15.20
- kbit/s. For the case of a frame length of 30 ms speech, the total
- number of bits used is 400, which fits in 50 bytes and results in a
- bit rate of 13.33 kbit/s. In the bitstream definition, the bits are
- distributed into three classes according to their bit error or loss
- sensitivity. The most sensitive bits (class 1) are placed first in
- the bitstream for each frame. The less sensitive bits (class 2) are
- placed after the class 1 bits. The least sensitive bits (class 3)
- are placed at the end of the bitstream for each frame.
- In the 20/30 ms frame length cases for each class, the following hold
- true: The class 1 bits occupy a total of 6/8 bytes (48/64 bits), the
- class 2 bits occupy 8/12 bytes (64/96 bits), and the class 3 bits
- occupy 24/30 bytes (191/239 bits). This distribution of the bits
- enables the use of uneven level protection (ULP) as is exploited in
- the payload format definition for iLBC [1]. The detailed bit
- allocation is shown in the table below. When a quantization index is
- distributed between more classes, the more significant bits belong to
- the lowest class.
- Andersen, et al. Experimental [Page 29]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Bitstream structure:
- ------------------------------------------------------------------+
- Parameter | Bits Class <1,2,3> |
- | 20 ms frame | 30 ms frame |
- ----------------------------------+---------------+---------------+
- Split 1 | 6 <6,0,0> | 6 <6,0,0> |
- LSF 1 Split 2 | 7 <7,0,0> | 7 <7,0,0> |
- LSF Split 3 | 7 <7,0,0> | 7 <7,0,0> |
- ------------------+---------------+---------------+
- Split 1 | NA (Not Appl.)| 6 <6,0,0> |
- LSF 2 Split 2 | NA | 7 <7,0,0> |
- Split 3 | NA | 7 <7,0,0> |
- ------------------+---------------+---------------+
- Sum | 20 <20,0,0> | 40 <40,0,0> |
- ----------------------------------+---------------+---------------+
- Block Class | 2 <2,0,0> | 3 <3,0,0> |
- ----------------------------------+---------------+---------------+
- Position 22 sample segment | 1 <1,0,0> | 1 <1,0,0> |
- ----------------------------------+---------------+---------------+
- Scale Factor State Coder | 6 <6,0,0> | 6 <6,0,0> |
- ----------------------------------+---------------+---------------+
- Sample 0 | 3 <0,1,2> | 3 <0,1,2> |
- Quantized Sample 1 | 3 <0,1,2> | 3 <0,1,2> |
- Residual : | : : | : : |
- State : | : : | : : |
- Samples : | : : | : : |
- Sample 56 | 3 <0,1,2> | 3 <0,1,2> |
- Sample 57 | NA | 3 <0,1,2> |
- ------------------+---------------+---------------+
- Sum | 171 <0,57,114>| 174 <0,58,116>|
- ----------------------------------+---------------+---------------+
- Stage 1 | 7 <6,0,1> | 7 <4,2,1> |
- CB for 22/23 Stage 2 | 7 <0,0,7> | 7 <0,0,7> |
- sample block Stage 3 | 7 <0,0,7> | 7 <0,0,7> |
- ------------------+---------------+---------------+
- Sum | 21 <6,0,15> | 21 <4,2,15> |
- ----------------------------------+---------------+---------------+
- Stage 1 | 5 <2,0,3> | 5 <1,1,3> |
- Gain for 22/23 Stage 2 | 4 <1,1,2> | 4 <1,1,2> |
- sample block Stage 3 | 3 <0,0,3> | 3 <0,0,3> |
- ------------------+---------------+---------------+
- Sum | 12 <3,1,8> | 12 <2,2,8> |
- ----------------------------------+---------------+---------------+
- Stage 1 | 8 <7,0,1> | 8 <6,1,1> |
- sub-block 1 Stage 2 | 7 <0,0,7> | 7 <0,0,7> |
- Stage 3 | 7 <0,0,7> | 7 <0,0,7> |
- ------------------+---------------+---------------+
- Andersen, et al. Experimental [Page 30]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Stage 1 | 8 <0,0,8> | 8 <0,7,1> |
- sub-block 2 Stage 2 | 8 <0,0,8> | 8 <0,0,8> |
- Indices Stage 3 | 8 <0,0,8> | 8 <0,0,8> |
- for CB ------------------+---------------+---------------+
- sub-blocks Stage 1 | NA | 8 <0,7,1> |
- sub-block 3 Stage 2 | NA | 8 <0,0,8> |
- Stage 3 | NA | 8 <0,0,8> |
- ------------------+---------------+---------------+
- Stage 1 | NA | 8 <0,7,1> |
- sub-block 4 Stage 2 | NA | 8 <0,0,8> |
- Stage 3 | NA | 8 <0,0,8> |
- ------------------+---------------+---------------+
- Sum | 46 <7,0,39> | 94 <6,22,66> |
- ----------------------------------+---------------+---------------+
- Stage 1 | 5 <1,2,2> | 5 <1,2,2> |
- sub-block 1 Stage 2 | 4 <1,1,2> | 4 <1,2,1> |
- Stage 3 | 3 <0,0,3> | 3 <0,0,3> |
- ------------------+---------------+---------------+
- Stage 1 | 5 <1,1,3> | 5 <0,2,3> |
- sub-block 2 Stage 2 | 4 <0,2,2> | 4 <0,2,2> |
- Stage 3 | 3 <0,0,3> | 3 <0,0,3> |
- Gains for ------------------+---------------+---------------+
- sub-blocks Stage 1 | NA | 5 <0,1,4> |
- sub-block 3 Stage 2 | NA | 4 <0,1,3> |
- Stage 3 | NA | 3 <0,0,3> |
- ------------------+---------------+---------------+
- Stage 1 | NA | 5 <0,1,4> |
- sub-block 4 Stage 2 | NA | 4 <0,1,3> |
- Stage 3 | NA | 3 <0,0,3> |
- ------------------+---------------+---------------+
- Sum | 24 <3,6,15> | 48 <2,12,34> |
- ----------------------------------+---------------+---------------+
- Empty frame indicator | 1 <0,0,1> | 1 <0,0,1> |
- -------------------------------------------------------------------
- SUM 304 <48,64,192> 400 <64,96,240>
- Table 3.2. The bitstream definition for iLBC for both the 20 ms
- frame size mode and the 30 ms frame size mode.
- When packetized into the payload, the bits MUST be sorted as follows:
- All the class 1 bits in the order (from top to bottom) as specified
- in the table, all the class 2 bits (from top to bottom), and all the
- class 3 bits in the same sequential order. The last bit, the empty
- frame indicator, SHOULD be set to zero by the encoder. If this bit
- is set to 1 the decoder SHOULD treat the data as a lost frame. For
- example, this bit can be set to 1 to indicate lost frame for file
- storage format, as in [1].
- Andersen, et al. Experimental [Page 31]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4. Decoder Principles
- This section describes the principles of each component of the
- decoder algorithm.
- +-------------+ +--------+ +---------------+
- payload -> | 1. Get para | -> | 2. LPC | -> | 3. Sc Dequant | ->
- +-------------+ +--------+ +---------------+
- +-------------+ +------------------+
- -> | 4. Mem setup| -> | 5. Construct res |------->
- | +-------------+ +------------------- |
- ---------<-----------<-----------<------------
- Sub-frame 0...2/4 (20 ms/30 ms)
- +----------------+ +----------+
- -> | 6. Enhance res | -> | 7. Synth | ------------>
- +----------------+ +----------+
- +-----------------+
- -> | 8. Post Process | ----------------> decoded speech
- +-----------------+
- Figure 4.1. Flow chart of the iLBC decoder. If a frame was lost,
- steps 1 to 5 SHOULD be replaced by a PLC algorithm.
- 1. Extract the parameters from the bitstream.
- 2. Decode the LPC and interpolate (section 4.1).
- 3. Construct the 57/58-sample start state (section 4.2).
- 4. Set up the memory by using data from the decoded residual. This
- memory is used for codebook construction. For blocks preceding
- the start state, both the decoded residual and the target are time
- reversed. Sub-frames are decoded in the same order as they were
- encoded.
- 5. Construct the residuals of this sub-frame (gain[0]*cbvec[0] +
- gain[1]*cbvec[1] + gain[2]*cbvec[2]). Repeat 4 and 5 until the
- residual of all sub-blocks has been constructed.
- 6. Enhance the residual with the post filter (section 4.6).
- 7. Synthesis of the residual (section 4.7).
- 8. Post process with HP filter, if desired (section 4.8).
- Andersen, et al. Experimental [Page 32]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4.1. LPC Filter Reconstruction
- The decoding of the LP filter parameters is very straightforward.
- For a set of three/six indices, the corresponding LSF vector(s) are
- found by simple table lookup. For each of the LSF vectors, the three
- split vectors are concatenated to obtain qlsf1 and qlsf2,
- respectively (in the 20 ms mode only one LSF vector, qlsf, is
- constructed). The next step is the stability check described in
- section 3.2.5 followed by the interpolation scheme described in
- section 3.2.6 (3.2.7 for 20 ms frames). The only difference is that
- only the quantized LSFs are known at the decoder, and hence the
- unquantized LSFs are not processed.
- A reference implementation of the LPC filter reconstruction is given
- in Appendix A.36.
- 4.2. Start State Reconstruction
- The scalar encoded STATE_SHORT_LEN=58 (STATE_SHORT_LEN=57 in the 20
- ms mode) state samples are reconstructed by 1) forming a set of
- samples (by table lookup) from the index stream idxVec[n], 2)
- multiplying the set with 1/scal=(10^qmax)/4.5, 3) time reversing the
- 57/58 samples, 4) filtering the time reversed block with the
- dispersion (all-pass) filter used in the encoder (as described in
- section 3.5.2); this compensates for the phase distortion of the
- earlier filter operation, and 5 reversing the 57/58 samples from the
- previous step.
- in(0..(STATE_SHORT_LEN-1)) = time reversed samples from table
- look-up,
- idxVecDec((STATE_SHORT_LEN-1)..0)
- in(STATE_SHORT_LEN..(2*STATE_SHORT_LEN-1)) = 0
- Pk(z) = A~rk(z)/A~k(z), where
- ___
- \
- A~rk(z)= z^(-LPC_FILTERORDER) + > a~ki*z^(i-(LPC_FILTERORDER-1))
- /__
- i=0...(LPC_FILTERORDER-1)
- and A~k(z) is taken from the block where the start state begins
- in -> Pk(z) -> filtered
- out(k) = filtered(STATE_SHORT_LEN-1-k) +
- filtered(2*STATE_SHORT_LEN-1-k),
- k=0..(STATE_SHORT_LEN-1)
- Andersen, et al. Experimental [Page 33]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- The remaining 23/22 samples in the state are reconstructed by the
- same adaptive codebook technique described in section 4.3. The
- location bit determines whether these are the first or the last 23/22
- samples of the 80-sample state vector. If the remaining 23/22
- samples are the first samples, then the scalar encoded
- STATE_SHORT_LEN state samples are time-reversed before initialization
- of the adaptive codebook memory vector.
- A reference implementation of the start state reconstruction is given
- in Appendix A.44.
- 4.3. Excitation Decoding Loop
- The decoding of the LPC excitation vector proceeds in the same order
- in which the residual was encoded at the encoder. That is, after the
- decoding of the entire 80-sample state vector, the forward sub-blocks
- (corresponding to samples occurring after the state vector samples)
- are decoded, and then the backward sub-blocks (corresponding to
- samples occurring before the state vector) are decoded, resulting in
- a fully decoded block of excitation signal samples.
- In particular, each sub-block is decoded by using the multistage
- adaptive codebook decoding module described in section 4.4. This
- module relies upon an adaptive codebook memory constructed before
- each run of the adaptive codebook decoding. The construction of the
- adaptive codebook memory in the decoder is identical to the method
- outlined in section 3.6.3, except that it is done on the codebook
- memory without perceptual weighting.
- For the initial forward sub-block, the last STATE_LEN=80 samples of
- the length CB_LMEM=147 adaptive codebook memory are filled with the
- samples of the state vector. For subsequent forward sub-blocks, the
- first SUBL=40 samples of the adaptive codebook memory are discarded,
- the remaining samples are shifted by SUBL samples toward the
- beginning of the vector, and the newly decoded SUBL=40 samples are
- placed at the end of the adaptive codebook memory. For backward
- sub-blocks, the construction is similar, except that every vector of
- samples involved is first time reversed.
- A reference implementation of the excitation decoding loop is found
- in Appendix A.5.
- Andersen, et al. Experimental [Page 34]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4.4. Multistage Adaptive Codebook Decoding
- The Multistage Adaptive Codebook Decoding module is used at both the
- sender (encoder) and the receiver (decoder) ends to produce a
- synthetic signal in the residual domain that is eventually used to
- produce synthetic speech. The module takes the index values used to
- construct vectors that are scaled and summed together to produce a
- synthetic signal that is the output of the module.
- 4.4.1. Construction of the Decoded Excitation Signal
- The unpacked index values provided at the input to the module are
- references to extended codebooks, which are constructed as described
- in section 3.6.3, except that they are based on the codebook memory
- without the perceptual weighting. The unpacked three indices are
- used to look up three codebook vectors. The unpacked three gain
- indices are used to decode the corresponding 3 gains. In this
- decoding, the successive rescaling, as described in section 3.6.4.2,
- is applied.
- A reference implementation of the adaptive codebook decoding is
- listed in Appendix A.32.
- 4.5. Packet Loss Concealment
- If packet loss occurs, the decoder receives a signal saying that
- information regarding a block is lost. For such blocks it is
- RECOMMENDED to use a Packet Loss Concealment (PLC) unit to create a
- decoded signal that masks the effect of that packet loss. In the
- following we will describe an example of a PLC unit that can be used
- with the iLBC codec. As the PLC unit is used only at the decoder,
- the PLC unit does not affect interoperability between
- implementations. Other PLC implementations MAY therefore be used.
- The PLC described operates on the LP filters and the excitation
- signals and is based on the following principles:
- 4.5.1. Block Received Correctly and Previous Block Also Received
- If the block is received correctly, the PLC only records state
- information of the current block that can be used in case the next
- block is lost. The LP filter coefficients for each sub-block and the
- entire decoded excitation signal are all saved in the decoder state
- structure. All of this information will be needed if the following
- block is lost.
- Andersen, et al. Experimental [Page 35]
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- 4.5.2. Block Not Received
- If the block is not received, the block substitution is based on a
- pitch-synchronous repetition of the excitation signal, which is
- filtered by the last LP filter of the previous block. The previous
- block's information is stored in the decoder state structure.
- A correlation analysis is performed on the previous block's
- excitation signal in order to detect the amount of pitch periodicity
- and a pitch value. The correlation measure is also used to decide on
- the voicing level (the degree to which the previous block's
- excitation was a voiced or roughly periodic signal). The excitation
- in the previous block is used to create an excitation for the block
- to be substituted, such that the pitch of the previous block is
- maintained. Therefore, the new excitation is constructed in a
- pitch-synchronous manner. In order to avoid a buzzy-sounding
- substituted block, a random excitation is mixed with the new pitch
- periodic excitation, and the relative use of the two components is
- computed from the correlation measure (voicing level).
- For the block to be substituted, the newly constructed excitation
- signal is then passed through the LP filter to produce the speech
- that will be substituted for the lost block.
- For several consecutive lost blocks, the packet loss concealment
- continues in a similar manner. The correlation measure of the last
- block received is still used along with the same pitch value. The LP
- filters of the last block received are also used again. The energy
- of the substituted excitation for consecutive lost blocks is
- decreased, leading to a dampened excitation, and therefore to
- dampened speech.
- 4.5.3. Block Received Correctly When Previous Block Not Received
- For the case in which a block is received correctly when the previous
- block was not, the correctly received block's directly decoded speech
- (based solely on the received block) is not used as the actual
- output. The reason for this is that the directly decoded speech does
- not necessarily smoothly merge into the synthetic speech generated
- for the previous lost block. If the two signals are not smoothly
- merged, an audible discontinuity is accidentally produced.
- Therefore, a correlation analysis between the two blocks of
- excitation signal (the excitation of the previous concealed block and
- that of the current received block) is performed to find the best
- phase match. Then a simple overlap-add procedure is performed to
- merge the previous excitation smoothly into the current block's
- excitation.
- Andersen, et al. Experimental [Page 36]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- The exact implementation of the packet loss concealment does not
- influence interoperability of the codec.
- A reference implementation of the packet loss concealment is
- suggested in Appendix A.14. Exact compliance with this suggested
- algorithm is not needed for a reference implementation to be fully
- compatible with the overall codec specification.
- 4.6. Enhancement
- The decoder contains an enhancement unit that operates on the
- reconstructed excitation signal. The enhancement unit increases the
- perceptual quality of the reconstructed signal by reducing the
- speech-correlated noise in the voiced speech segments. Compared to
- traditional postfilters, the enhancer has an advantage in that it can
- only modify the excitation signal slightly. This means that there is
- no risk of over enhancement. The enhancer works very similarly for
- both the 20 ms frame size mode and the 30 ms frame size mode.
- For the mode with 20 ms frame size, the enhancer uses a memory of six
- 80-sample excitation blocks prior in time plus the two new 80-sample
- excitation blocks. For each block of 160 new unenhanced excitation
- samples, 160 enhanced excitation samples are produced. The enhanced
- excitation is 40-sample delayed compared to the unenhanced
- excitation, as the enhancer algorithm uses lookahead.
- For the mode with 30 ms frame size, the enhancer uses a memory of
- five 80-sample excitation blocks prior in time plus the three new
- 80-sample excitation blocks. For each block of 240 new unenhanced
- excitation samples, 240 enhanced excitation samples are produced.
- The enhanced excitation is 80-sample delayed compared to the
- unenhanced excitation, as the enhancer algorithm uses lookahead.
- Outline of Enhancer
- The speech enhancement unit operates on sub-blocks of 80 samples,
- which means that there are two/three 80 sample sub-blocks per frame.
- Each of these two/three sub-blocks is enhanced separately, but in an
- analogous manner.
- Andersen, et al. Experimental [Page 37]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- unenhanced residual
- |
- | +---------------+ +--------------+
- +-> | 1. Pitch Est | -> | 2. Find PSSQ | -------->
- +---------------+ | +--------------+
- +-----<-------<------<--+
- +------------+ enh block 0..1/2 |
- -> | 3. Smooth | |
- +------------+ |
- \ |
- /\ |
- / \ Already |
- / 4. \----------->----------->-----------+ |
- \Crit/ Fulfilled | |
- \? / v |
- \/ | |
- \ +-----------------+ +---------+ | |
- Not +->| 5. Use Constr. | -> | 6. Mix | ----->
- Fulfilled +-----------------+ +---------+
- ---------------> enhanced residual
- Figure 4.2. Flow chart of the enhancer.
- 1. Pitch estimation of each of the two/three new 80-sample blocks.
- 2. Find the pitch-period-synchronous sequence n (for block k) by a
- search around the estimated pitch value. Do this for n=1,2,3,
- -1,-2,-3.
- 3. Calculate the smoothed residual generated by the six pitch-
- period-synchronous sequences from prior step.
- 4. Check if the smoothed residual satisfies the criterion (section
- 4.6.4).
- 5. Use constraint to calculate mixing factor (section 4.6.5).
- 6. Mix smoothed signal with unenhanced residual (pssq(n) n=0).
- The main idea of the enhancer is to find three 80 sample blocks
- before and three 80-sample blocks after the analyzed unenhanced sub-
- block and to use these to improve the quality of the excitation in
- that sub-block. The six blocks are chosen so that they have the
- highest possible correlation with the unenhanced sub-block that is
- being enhanced. In other words, the six blocks are pitch-period-
- synchronous sequences to the unenhanced sub-block.
- Andersen, et al. Experimental [Page 38]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A linear combination of the six pitch-period-synchronous sequences is
- calculated that approximates the sub-block. If the squared error
- between the approximation and the unenhanced sub-block is small
- enough, the enhanced residual is set equal to this approximation.
- For the cases when the squared error criterion is not fulfilled, a
- linear combination of the approximation and the unenhanced residual
- forms the enhanced residual.
- 4.6.1. Estimating the Pitch
- Pitch estimates are needed to determine the locations of the pitch-
- period-synchronous sequences in a complexity-efficient way. For each
- of the new two/three sub-blocks, a pitch estimate is calculated by
- finding the maximum correlation in the range from lag 20 to lag 120.
- These pitch estimates are used to narrow down the search for the best
- possible pitch-period-synchronous sequences.
- 4.6.2. Determination of the Pitch-Synchronous Sequences
- Upon receiving the pitch estimates from the prior step, the enhancer
- analyzes and enhances one 80-sample sub-block at a time. The pitch-
- period-synchronous-sequences pssq(n) can be viewed as vectors of
- length 80 samples each shifted n*lag samples from the current sub-
- block. The six pitch-period-synchronous-sequences, pssq(-3) to
- pssq(-1) and pssq(1) to pssq(3), are found one at a time by the steps
- below:
- 1) Calculate the estimate of the position of the pssq(n). For
- pssq(n) in front of pssq(0) (n > 0), the location of the pssq(n)
- is estimated by moving one pitch estimate forward in time from the
- exact location of pssq(n-1). Similarly, pssq(n) behind pssq(0) (n
- < 0) is estimated by moving one pitch estimate backward in time
- from the exact location of pssq(n+1). If the estimated pssq(n)
- vector location is totally within the enhancer memory (Figure
- 4.3), steps 2, 3, and 4 are performed, otherwise the pssq(n) is
- set to zeros.
- 2) Compute the correlation between the unenhanced excitation and
- vectors around the estimated location interval of pssq(n). The
- correlation is calculated in the interval estimated location +/- 2
- samples. This results in five correlation values.
- 3) The five correlation values are upsampled by a factor of 4, by
- using four simple upsampling filters (MA filters with coefficients
- upsFilter1.. upsFilter4). Within these the maximum value is
- found, which specifies the best pitch-period with a resolution of
- a quarter of a sample.
- Andersen, et al. Experimental [Page 39]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- upsFilter1[7]={0.000000 0.000000 0.000000 1.000000
- 0.000000 0.000000 0.000000}
- upsFilter2[7]={0.015625 -0.076904 0.288330 0.862061
- -0.106445 0.018799 -0.015625}
- upsFilter3[7]={0.023682 -0.124268 0.601563 0.601563
- -0.124268 0.023682 -0.023682}
- upsFilter4[7]={0.018799 -0.106445 0.862061 0.288330
- -0.076904 0.015625 -0.018799}
- 4) Generate the pssq(n) vector by upsampling of the excitation memory
- and extracting the sequence that corresponds to the lag delay that
- was calculated in prior step.
- With the steps above, all the pssq(n) can be found in an iterative
- manner, first moving backward in time from pssq(0) and then forward
- in time from pssq(0).
- 0 159 319 479 639
- +---------------------------------------------------------------+
- | -5 | -4 | -3 | -2 | -1 | 0 | 1 | 2 |
- +---------------------------------------------------------------+
- |pssq 0 |
- |pssq -1| |pssq 1 |
- |pssq -2| |pssq 2 |
- |pssq -3| |pssq 3 |
- Figure 4.3. Enhancement for 20 ms frame size.
- Figure 4.3 depicts pitch-period-synchronous sequences in the
- enhancement of the first 80 sample block in the 20 ms frame size
- mode. The unenhanced signal input is stored in the last two sub-
- blocks (1 - 2), and the six other sub-blocks contain unenhanced
- residual prior-in-time. We perform the enhancement algorithm on two
- blocks of 80 samples, where the first of the two blocks consists of
- the last 40 samples of sub-block 0 and the first 40 samples of sub-
- block 1. The second 80-sample block consists of the last 40 samples
- of sub-block 1 and the first 40 samples of sub-block 2.
- Andersen, et al. Experimental [Page 40]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 0 159 319 479 639
- +---------------------------------------------------------------+
- | -4 | -3 | -2 | -1 | 0 | 1 | 2 | 3 |
- +---------------------------------------------------------------+
- |pssq 0 |
- |pssq -1| |pssq 1 |
- |pssq -2| |pssq 2 |
- |pssq -3| |pssq 3 |
- Figure 4.4. Enhancement for 30 ms frame size.
- Figure 4.4 depicts pitch-period-synchronous sequences in the
- enhancement of the first 80-sample block in the 30 ms frame size
- mode. The unenhanced signal input is stored in the last three sub-
- blocks (1 - 3). The five other sub-blocks contain unenhanced
- residual prior-in-time. The enhancement algorithm is performed on
- the three 80 sample sub-blocks 0, 1, and 2.
- 4.6.3. Calculation of the Smoothed Excitation
- A linear combination of the six pssq(n) (n!=0) form a smoothed
- approximation, z, of pssq(0). Most of the weight is put on the
- sequences that are close to pssq(0), as these are likely to be most
- similar to pssq(0). The smoothed vector is also rescaled so that the
- energy of z is the same as the energy of pssq(0).
- ___
- \
- y = > pssq(i) * pssq_weight(i)
- /__
- i=-3,-2,-1,1,2,3
- pssq_weight(i) = 0.5*(1-cos(2*pi*(i+4)/(2*3+2)))
- z = C * y, where C = ||pssq(0)||/||y||
- 4.6.4. Enhancer Criterion
- The criterion of the enhancer is that the enhanced excitation is not
- allowed to differ much from the unenhanced excitation. This
- criterion is checked for each 80-sample sub-block.
- e < (b * ||pssq(0)||^2), where b=0.05 and (Constraint 1)
- e = (pssq(0)-z)*(pssq(0)-z), and "*" means the dot product
- Andersen, et al. Experimental [Page 41]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4.6.5. Enhancing the excitation
- From the criterion in the previous section, it is clear that the
- excitation is not allowed to change much. The purpose of this
- constraint is to prevent the creation of an enhanced signal
- significantly different from the original signal. This also means
- that the constraint limits the numerical size of the errors that the
- enhancement procedure can make. That is especially important in
- unvoiced segments and background noise segments for which increased
- periodicity could lead to lower perceived quality.
- When the constraint in the prior section is not met, the enhanced
- residual is instead calculated through a constrained optimization by
- using the Lagrange multiplier technique. The new constraint is that
- e = (b * ||pssq(0)||^2) (Constraint 2)
- We distinguish two solution regions for the optimization: 1) the
- region where the first constraint is fulfilled and 2) the region
- where the first constraint is not fulfilled and the second constraint
- must be used.
- In the first case, where the second constraint is not needed, the
- optimized re-estimated vector is simply z, the energy-scaled version
- of y.
- In the second case, where the second constraint is activated and
- becomes an equality constraint, we have
- z= A*y + B*pssq(0)
- where
- A = sqrt((b-b^2/4)*(w00*w00)/ (w11*w00 + w10*w10)) and
- w11 = pssq(0)*pssq(0)
- w00 = y*y
- w10 = y*pssq(0) (* symbolizes the dot product)
- and
- B = 1 - b/2 - A * w10/w00
- Appendix A.16 contains a listing of a reference implementation for
- the enhancement method.
- Andersen, et al. Experimental [Page 42]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- 4.7. Synthesis Filtering
- Upon decoding or PLC of the LP excitation block, the decoded speech
- block is obtained by running the decoded LP synthesis filter,
- 1/A~k(z), over the block. The synthesis filters have to be shifted
- to compensate for the delay in the enhancer. For 20 ms frame size
- mode, they SHOULD be shifted one 40-sample sub-block, and for 30 ms
- frame size mode, they SHOULD be shifted two 40-sample sub-blocks.
- The LP coefficients SHOULD be changed at the first sample of every
- sub-block while keeping the filter state. For PLC blocks, one
- solution is to apply the last LP coefficients of the last decoded
- speech block for all sub-blocks.
- The reference implementation for the synthesis filtering can be found
- in Appendix A.48.
- 4.8. Post Filtering
- If desired, the decoded block can be filtered by a high-pass filter.
- This removes the low frequencies of the decoded signal. A reference
- implementation of this, with cutoff at 65 Hz, is shown in Appendix
- A.30.
- 5. Security Considerations
- This algorithm for the coding of speech signals is not subject to any
- known security consideration; however, its RTP payload format [1] is
- subject to several considerations, which are addressed there.
- Confidentiality of the media streams is achieved by encryption;
- therefore external mechanisms, such as SRTP [5], MAY be used for that
- purpose.
- 6. Evaluation of the iLBC Implementations
- It is possible and suggested to evaluate certain iLBC implementation
- by utilizing methodology and tools available at
- http://www.ilbcfreeware.org/evaluation.html
- 7. References
- 7.1. Normative References
- [1] Duric, A. and S. Andersen, "Real-time Transport Protocol (RTP)
- Payload Format for internet Low Bit Rate Codec (iLBC) Speech",
- RFC 3952, December 2004.
- [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
- Levels", BCP 14, RFC 2119, March 1997.
- Andersen, et al. Experimental [Page 43]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- [3] PacketCable(TM) Audio/Video Codecs Specification, Cable
- Television Laboratories, Inc.
- 7.2. Informative References
- [4] ITU-T Recommendation G.711, available online from the ITU
- bookstore at http://www.itu.int.
- [5] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norman,
- "The Secure Real Time Transport Protocol (SRTP)", RFC 3711, March
- 2004.
- 8. Acknowledgements
- This extensive work, besides listed authors, has the following
- authors, who could not have been listed among "official" authors (due
- to IESG restrictions in the number of authors who can be listed):
- Manohar N. Murthi (Department of Electrical and Computer
- Engineering, University of Miami), Fredrik Galschiodt, Julian
- Spittka, and Jan Skoglund (Global IP Sound).
- The authors are deeply indebted to the following people and thank
- them sincerely:
- Henry Sinnreich, Patrik Faltstrom, Alan Johnston, and Jean-
- Francois Mule for great support of the iLBC initiative and for
- valuable feedback and comments.
- Peter Vary, Frank Mertz, and Christoph Erdmann (RWTH Aachen);
- Vladimir Cuperman (Niftybox LLC); Thomas Eriksson (Chalmers Univ
- of Tech), and Gernot Kubin (TU Graz), for thorough review of the
- iLBC document and their valuable feedback and remarks.
- Andersen, et al. Experimental [Page 44]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- APPENDIX A. Reference Implementation
- This appendix contains the complete c-code for a reference
- implementation of encoder and decoder for the specified codec.
- The c-code consists of the following files with highest-level
- functions:
- iLBC_test.c: main function for evaluation purpose
- iLBC_encode.h: encoder header
- iLBC_encode.c: encoder function
- iLBC_decode.h: decoder header
- iLBC_decode.c: decoder function
- The following files contain global defines and constants:
- iLBC_define.h: global defines
- constants.h: global constants header
- constants.c: global constants memory allocations
- The following files contain subroutines:
- anaFilter.h: lpc analysis filter header
- anaFilter.c: lpc analysis filter function
- createCB.h: codebook construction header
- createCB.c: codebook construction function
- doCPLC.h: packet loss concealment header
- doCPLC.c: packet loss concealment function
- enhancer.h: signal enhancement header
- enhancer.c: signal enhancement function
- filter.h: general filter header
- filter.c: general filter functions
- FrameClassify.h: start state classification header
- FrameClassify.c: start state classification function
- gainquant.h: gain quantization header
- gainquant.c: gain quantization function
- getCBvec.h: codebook vector construction header
- getCBvec.c: codebook vector construction function
- helpfun.h: general purpose header
- helpfun.c: general purpose functions
- hpInput.h: input high pass filter header
- hpInput.c: input high pass filter function
- hpOutput.h: output high pass filter header
- hpOutput.c: output high pass filter function
- iCBConstruct.h: excitation decoding header
- iCBConstruct.c: excitation decoding function
- iCBSearch.h: excitation encoding header
- iCBSearch.c: excitation encoding function
- Andersen, et al. Experimental [Page 45]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- LPCdecode.h: lpc decoding header
- LPCdecode.c: lpc decoding function
- LPCencode.h: lpc encoding header
- LPCencode.c: lpc encoding function
- lsf.h: line spectral frequencies header
- lsf.c: line spectral frequencies functions
- packing.h: bitstream packetization header
- packing.c: bitstream packetization functions
- StateConstructW.h: state decoding header
- StateConstructW.c: state decoding functions
- StateSearchW.h: state encoding header
- StateSearchW.c: state encoding function
- syntFilter.h: lpc synthesis filter header
- syntFilter.c: lpc synthesis filter function
- The implementation is portable and should work on many different
- platforms. However, it is not difficult to optimize the
- implementation on particular platforms, an exercise left to the
- reader.
- A.1. iLBC_test.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_test.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <stdlib.h>
- #include <stdio.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "iLBC_encode.h"
- #include "iLBC_decode.h"
- /* Runtime statistics */
- #include <time.h>
- #define ILBCNOOFWORDS_MAX (NO_OF_BYTES_30MS/2)
- /*----------------------------------------------------------------*
- * Encoder interface function
- Andersen, et al. Experimental [Page 46]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- *---------------------------------------------------------------*/
- short encode( /* (o) Number of bytes encoded */
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i/o) Encoder instance */
- short *encoded_data, /* (o) The encoded bytes */
- short *data /* (i) The signal block to encode*/
- ){
- float block[BLOCKL_MAX];
- int k;
- /* convert signal to float */
- for (k=0; k<iLBCenc_inst->blockl; k++)
- block[k] = (float)data[k];
- /* do the actual encoding */
- iLBC_encode((unsigned char *)encoded_data, block, iLBCenc_inst);
- return (iLBCenc_inst->no_of_bytes);
- }
- /*----------------------------------------------------------------*
- * Decoder interface function
- *---------------------------------------------------------------*/
- short decode( /* (o) Number of decoded samples */
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */
- short *decoded_data, /* (o) Decoded signal block*/
- short *encoded_data, /* (i) Encoded bytes */
- short mode /* (i) 0=PL, 1=Normal */
- ){
- int k;
- float decblock[BLOCKL_MAX], dtmp;
- /* check if mode is valid */
- if (mode<0 || mode>1) {
- printf("\nERROR - Wrong mode - 0, 1 allowed\n"); exit(3);}
- /* do actual decoding of block */
- iLBC_decode(decblock, (unsigned char *)encoded_data,
- iLBCdec_inst, mode);
- /* convert to short */
- Andersen, et al. Experimental [Page 47]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (k=0; k<iLBCdec_inst->blockl; k++){
- dtmp=decblock[k];
- if (dtmp<MIN_SAMPLE)
- dtmp=MIN_SAMPLE;
- else if (dtmp>MAX_SAMPLE)
- dtmp=MAX_SAMPLE;
- decoded_data[k] = (short) dtmp;
- }
- return (iLBCdec_inst->blockl);
- }
- /*---------------------------------------------------------------*
- * Main program to test iLBC encoding and decoding
- *
- * Usage:
- * exefile_name.exe <infile> <bytefile> <outfile> <channel>
- *
- * <infile> : Input file, speech for encoder (16-bit pcm file)
- * <bytefile> : Bit stream output from the encoder
- * <outfile> : Output file, decoded speech (16-bit pcm file)
- * <channel> : Bit error file, optional (16-bit)
- * 1 - Packet received correctly
- * 0 - Packet Lost
- *
- *--------------------------------------------------------------*/
- int main(int argc, char* argv[])
- {
- /* Runtime statistics */
- float starttime;
- float runtime;
- float outtime;
- FILE *ifileid,*efileid,*ofileid, *cfileid;
- short data[BLOCKL_MAX];
- short encoded_data[ILBCNOOFWORDS_MAX], decoded_data[BLOCKL_MAX];
- int len;
- short pli, mode;
- int blockcount = 0;
- int packetlosscount = 0;
- /* Create structs */
- iLBC_Enc_Inst_t Enc_Inst;
- iLBC_Dec_Inst_t Dec_Inst;
- Andersen, et al. Experimental [Page 48]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* get arguments and open files */
- if ((argc!=5) && (argc!=6)) {
- fprintf(stderr,
- "\n*-----------------------------------------------*\n");
- fprintf(stderr,
- " %s <20,30> input encoded decoded (channel)\n\n",
- argv[0]);
- fprintf(stderr,
- " mode : Frame size for the encoding/decoding\n");
- fprintf(stderr,
- " 20 - 20 ms\n");
- fprintf(stderr,
- " 30 - 30 ms\n");
- fprintf(stderr,
- " input : Speech for encoder (16-bit pcm file)\n");
- fprintf(stderr,
- " encoded : Encoded bit stream\n");
- fprintf(stderr,
- " decoded : Decoded speech (16-bit pcm file)\n");
- fprintf(stderr,
- " channel : Packet loss pattern, optional (16-bit)\n");
- fprintf(stderr,
- " 1 - Packet received correctly\n");
- fprintf(stderr,
- " 0 - Packet Lost\n");
- fprintf(stderr,
- "*-----------------------------------------------*\n\n");
- exit(1);
- }
- mode=atoi(argv[1]);
- if (mode != 20 && mode != 30) {
- fprintf(stderr,"Wrong mode %s, must be 20, or 30\n",
- argv[1]);
- exit(2);
- }
- if ( (ifileid=fopen(argv[2],"rb")) == NULL) {
- fprintf(stderr,"Cannot open input file %s\n", argv[2]);
- exit(2);}
- if ( (efileid=fopen(argv[3],"wb")) == NULL) {
- fprintf(stderr, "Cannot open encoded file %s\n",
- argv[3]); exit(1);}
- if ( (ofileid=fopen(argv[4],"wb")) == NULL) {
- fprintf(stderr, "Cannot open decoded file %s\n",
- argv[4]); exit(1);}
- if (argc==6) {
- if( (cfileid=fopen(argv[5],"rb")) == NULL) {
- fprintf(stderr, "Cannot open channel file %s\n",
- Andersen, et al. Experimental [Page 49]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- argv[5]);
- exit(1);
- }
- } else {
- cfileid=NULL;
- }
- /* print info */
- fprintf(stderr, "\n");
- fprintf(stderr,
- "*---------------------------------------------------*\n");
- fprintf(stderr,
- "* *\n");
- fprintf(stderr,
- "* iLBC test program *\n");
- fprintf(stderr,
- "* *\n");
- fprintf(stderr,
- "* *\n");
- fprintf(stderr,
- "*---------------------------------------------------*\n");
- fprintf(stderr,"\nMode : %2d ms\n", mode);
- fprintf(stderr,"Input file : %s\n", argv[2]);
- fprintf(stderr,"Encoded file : %s\n", argv[3]);
- fprintf(stderr,"Output file : %s\n", argv[4]);
- if (argc==6) {
- fprintf(stderr,"Channel file : %s\n", argv[5]);
- }
- fprintf(stderr,"\n");
- /* Initialization */
- initEncode(&Enc_Inst, mode);
- initDecode(&Dec_Inst, mode, 1);
- /* Runtime statistics */
- starttime=clock()/(float)CLOCKS_PER_SEC;
- /* loop over input blocks */
- while (fread(data,sizeof(short),Enc_Inst.blockl,ifileid)==
- Enc_Inst.blockl) {
- blockcount++;
- /* encoding */
- Andersen, et al. Experimental [Page 50]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- fprintf(stderr, "--- Encoding block %i --- ",blockcount);
- len=encode(&Enc_Inst, encoded_data, data);
- fprintf(stderr, "\r");
- /* write byte file */
- fwrite(encoded_data, sizeof(unsigned char), len, efileid);
- /* get channel data if provided */
- if (argc==6) {
- if (fread(&pli, sizeof(short), 1, cfileid)) {
- if ((pli!=0)&&(pli!=1)) {
- fprintf(stderr, "Error in channel file\n");
- exit(0);
- }
- if (pli==0) {
- /* Packet loss -> remove info from frame */
- memset(encoded_data, 0,
- sizeof(short)*ILBCNOOFWORDS_MAX);
- packetlosscount++;
- }
- } else {
- fprintf(stderr, "Error. Channel file too short\n");
- exit(0);
- }
- } else {
- pli=1;
- }
- /* decoding */
- fprintf(stderr, "--- Decoding block %i --- ",blockcount);
- len=decode(&Dec_Inst, decoded_data, encoded_data, pli);
- fprintf(stderr, "\r");
- /* write output file */
- fwrite(decoded_data,sizeof(short),len,ofileid);
- }
- /* Runtime statistics */
- runtime = (float)(clock()/(float)CLOCKS_PER_SEC-starttime);
- outtime = (float)((float)blockcount*(float)mode/1000.0);
- printf("\n\nLength of speech file: %.1f s\n", outtime);
- printf("Packet loss : %.1f%%\n",
- 100.0*(float)packetlosscount/(float)blockcount);
- Andersen, et al. Experimental [Page 51]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- printf("Time to run iLBC :");
- printf(" %.1f s (%.1f %% of realtime)\n\n", runtime,
- (100*runtime/outtime));
- /* close files */
- fclose(ifileid); fclose(efileid); fclose(ofileid);
- if (argc==6) {
- fclose(cfileid);
- }
- return(0);
- }
- A.2. iLBC_encode.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_encode.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_ILBCENCODE_H
- #define __iLBC_ILBCENCODE_H
- #include "iLBC_define.h"
- short initEncode( /* (o) Number of bytes
- encoded */
- iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */
- int mode /* (i) frame size mode */
- );
- void iLBC_encode(
- unsigned char *bytes, /* (o) encoded data bits iLBC */
- float *block, /* (o) speech vector to
- encode */
- iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder
- state */
- );
- #endif
- Andersen, et al. Experimental [Page 52]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.3. iLBC_encode.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_encode.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <stdlib.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "LPCencode.h"
- #include "FrameClassify.h"
- #include "StateSearchW.h"
- #include "StateConstructW.h"
- #include "helpfun.h"
- #include "constants.h"
- #include "packing.h"
- #include "iCBSearch.h"
- #include "iCBConstruct.h"
- #include "hpInput.h"
- #include "anaFilter.h"
- #include "syntFilter.h"
- /*----------------------------------------------------------------*
- * Initiation of encoder instance.
- *---------------------------------------------------------------*/
- short initEncode( /* (o) Number of bytes
- encoded */
- iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */
- int mode /* (i) frame size mode */
- ){
- iLBCenc_inst->mode = mode;
- if (mode==30) {
- iLBCenc_inst->blockl = BLOCKL_30MS;
- iLBCenc_inst->nsub = NSUB_30MS;
- iLBCenc_inst->nasub = NASUB_30MS;
- iLBCenc_inst->lpc_n = LPC_N_30MS;
- iLBCenc_inst->no_of_bytes = NO_OF_BYTES_30MS;
- iLBCenc_inst->no_of_words = NO_OF_WORDS_30MS;
- Andersen, et al. Experimental [Page 53]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- iLBCenc_inst->state_short_len=STATE_SHORT_LEN_30MS;
- /* ULP init */
- iLBCenc_inst->ULP_inst=&ULP_30msTbl;
- }
- else if (mode==20) {
- iLBCenc_inst->blockl = BLOCKL_20MS;
- iLBCenc_inst->nsub = NSUB_20MS;
- iLBCenc_inst->nasub = NASUB_20MS;
- iLBCenc_inst->lpc_n = LPC_N_20MS;
- iLBCenc_inst->no_of_bytes = NO_OF_BYTES_20MS;
- iLBCenc_inst->no_of_words = NO_OF_WORDS_20MS;
- iLBCenc_inst->state_short_len=STATE_SHORT_LEN_20MS;
- /* ULP init */
- iLBCenc_inst->ULP_inst=&ULP_20msTbl;
- }
- else {
- exit(2);
- }
- memset((*iLBCenc_inst).anaMem, 0,
- LPC_FILTERORDER*sizeof(float));
- memcpy((*iLBCenc_inst).lsfold, lsfmeanTbl,
- LPC_FILTERORDER*sizeof(float));
- memcpy((*iLBCenc_inst).lsfdeqold, lsfmeanTbl,
- LPC_FILTERORDER*sizeof(float));
- memset((*iLBCenc_inst).lpc_buffer, 0,
- (LPC_LOOKBACK+BLOCKL_MAX)*sizeof(float));
- memset((*iLBCenc_inst).hpimem, 0, 4*sizeof(float));
- return (iLBCenc_inst->no_of_bytes);
- }
- /*----------------------------------------------------------------*
- * main encoder function
- *---------------------------------------------------------------*/
- void iLBC_encode(
- unsigned char *bytes, /* (o) encoded data bits iLBC */
- float *block, /* (o) speech vector to
- encode */
- iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder
- state */
- ){
- float data[BLOCKL_MAX];
- float residual[BLOCKL_MAX], reverseResidual[BLOCKL_MAX];
- int start, idxForMax, idxVec[STATE_LEN];
- Andersen, et al. Experimental [Page 54]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML];
- int n, k, meml_gotten, Nfor, Nback, i, pos;
- int gain_index[CB_NSTAGES*NASUB_MAX],
- extra_gain_index[CB_NSTAGES];
- int cb_index[CB_NSTAGES*NASUB_MAX],extra_cb_index[CB_NSTAGES];
- int lsf_i[LSF_NSPLIT*LPC_N_MAX];
- unsigned char *pbytes;
- int diff, start_pos, state_first;
- float en1, en2;
- int index, ulp, firstpart;
- int subcount, subframe;
- float weightState[LPC_FILTERORDER];
- float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
- float weightdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
- float decresidual[BLOCKL_MAX];
- /* high pass filtering of input signal if such is not done
- prior to calling this function */
- hpInput(block, iLBCenc_inst->blockl,
- data, (*iLBCenc_inst).hpimem);
- /* otherwise simply copy */
- /*memcpy(data,block,iLBCenc_inst->blockl*sizeof(float));*/
- /* LPC of hp filtered input data */
- LPCencode(syntdenum, weightdenum, lsf_i, data, iLBCenc_inst);
- /* inverse filter to get residual */
- for (n=0; n<iLBCenc_inst->nsub; n++) {
- anaFilter(&data[n*SUBL], &syntdenum[n*(LPC_FILTERORDER+1)],
- SUBL, &residual[n*SUBL], iLBCenc_inst->anaMem);
- }
- /* find state location */
- start = FrameClassify(iLBCenc_inst, residual);
- /* check if state should be in first or last part of the
- two subframes */
- diff = STATE_LEN - iLBCenc_inst->state_short_len;
- en1 = 0;
- index = (start-1)*SUBL;
- Andersen, et al. Experimental [Page 55]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (i = 0; i < iLBCenc_inst->state_short_len; i++) {
- en1 += residual[index+i]*residual[index+i];
- }
- en2 = 0;
- index = (start-1)*SUBL+diff;
- for (i = 0; i < iLBCenc_inst->state_short_len; i++) {
- en2 += residual[index+i]*residual[index+i];
- }
- if (en1 > en2) {
- state_first = 1;
- start_pos = (start-1)*SUBL;
- } else {
- state_first = 0;
- start_pos = (start-1)*SUBL + diff;
- }
- /* scalar quantization of state */
- StateSearchW(iLBCenc_inst, &residual[start_pos],
- &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
- &weightdenum[(start-1)*(LPC_FILTERORDER+1)], &idxForMax,
- idxVec, iLBCenc_inst->state_short_len, state_first);
- StateConstructW(idxForMax, idxVec,
- &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
- &decresidual[start_pos], iLBCenc_inst->state_short_len);
- /* predictive quantization in state */
- if (state_first) { /* put adaptive part in the end */
- /* setup memory */
- memset(mem, 0,
- (CB_MEML-iLBCenc_inst->state_short_len)*sizeof(float));
- memcpy(mem+CB_MEML-iLBCenc_inst->state_short_len,
- decresidual+start_pos,
- iLBCenc_inst->state_short_len*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- /* encode sub-frames */
- iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index,
- &residual[start_pos+iLBCenc_inst->state_short_len],
- mem+CB_MEML-stMemLTbl,
- stMemLTbl, diff, CB_NSTAGES,
- Andersen, et al. Experimental [Page 56]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- &weightdenum[start*(LPC_FILTERORDER+1)],
- weightState, 0);
- /* construct decoded vector */
- iCBConstruct(
- &decresidual[start_pos+iLBCenc_inst->state_short_len],
- extra_cb_index, extra_gain_index,
- mem+CB_MEML-stMemLTbl,
- stMemLTbl, diff, CB_NSTAGES);
- }
- else { /* put adaptive part in the beginning */
- /* create reversed vectors for prediction */
- for (k=0; k<diff; k++) {
- reverseResidual[k] = residual[(start+1)*SUBL-1
- -(k+iLBCenc_inst->state_short_len)];
- }
- /* setup memory */
- meml_gotten = iLBCenc_inst->state_short_len;
- for (k=0; k<meml_gotten; k++) {
- mem[CB_MEML-1-k] = decresidual[start_pos + k];
- }
- memset(mem, 0, (CB_MEML-k)*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- /* encode sub-frames */
- iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index,
- reverseResidual, mem+CB_MEML-stMemLTbl, stMemLTbl,
- diff, CB_NSTAGES,
- &weightdenum[(start-1)*(LPC_FILTERORDER+1)],
- weightState, 0);
- /* construct decoded vector */
- iCBConstruct(reverseDecresidual, extra_cb_index,
- extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl,
- diff, CB_NSTAGES);
- /* get decoded residual from reversed vector */
- for (k=0; k<diff; k++) {
- decresidual[start_pos-1-k] = reverseDecresidual[k];
- Andersen, et al. Experimental [Page 57]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- }
- /* counter for predicted sub-frames */
- subcount=0;
- /* forward prediction of sub-frames */
- Nfor = iLBCenc_inst->nsub-start-1;
- if ( Nfor > 0 ) {
- /* setup memory */
- memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float));
- memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL,
- STATE_LEN*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- /* loop over sub-frames to encode */
- for (subframe=0; subframe<Nfor; subframe++) {
- /* encode sub-frame */
- iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES,
- gain_index+subcount*CB_NSTAGES,
- &residual[(start+1+subframe)*SUBL],
- mem+CB_MEML-memLfTbl[subcount],
- memLfTbl[subcount], SUBL, CB_NSTAGES,
- &weightdenum[(start+1+subframe)*
- (LPC_FILTERORDER+1)],
- weightState, subcount+1);
- /* construct decoded vector */
- iCBConstruct(&decresidual[(start+1+subframe)*SUBL],
- cb_index+subcount*CB_NSTAGES,
- gain_index+subcount*CB_NSTAGES,
- mem+CB_MEML-memLfTbl[subcount],
- memLfTbl[subcount], SUBL, CB_NSTAGES);
- /* update memory */
- memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
- memcpy(mem+CB_MEML-SUBL,
- Andersen, et al. Experimental [Page 58]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- &decresidual[(start+1+subframe)*SUBL],
- SUBL*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- subcount++;
- }
- }
- /* backward prediction of sub-frames */
- Nback = start-1;
- if ( Nback > 0 ) {
- /* create reverse order vectors */
- for (n=0; n<Nback; n++) {
- for (k=0; k<SUBL; k++) {
- reverseResidual[n*SUBL+k] =
- residual[(start-1)*SUBL-1-n*SUBL-k];
- reverseDecresidual[n*SUBL+k] =
- decresidual[(start-1)*SUBL-1-n*SUBL-k];
- }
- }
- /* setup memory */
- meml_gotten = SUBL*(iLBCenc_inst->nsub+1-start);
- if ( meml_gotten > CB_MEML ) {
- meml_gotten=CB_MEML;
- }
- for (k=0; k<meml_gotten; k++) {
- mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k];
- }
- memset(mem, 0, (CB_MEML-k)*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- /* loop over sub-frames to encode */
- for (subframe=0; subframe<Nback; subframe++) {
- /* encode sub-frame */
- iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES,
- Andersen, et al. Experimental [Page 59]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- gain_index+subcount*CB_NSTAGES,
- &reverseResidual[subframe*SUBL],
- mem+CB_MEML-memLfTbl[subcount],
- memLfTbl[subcount], SUBL, CB_NSTAGES,
- &weightdenum[(start-2-subframe)*
- (LPC_FILTERORDER+1)],
- weightState, subcount+1);
- /* construct decoded vector */
- iCBConstruct(&reverseDecresidual[subframe*SUBL],
- cb_index+subcount*CB_NSTAGES,
- gain_index+subcount*CB_NSTAGES,
- mem+CB_MEML-memLfTbl[subcount],
- memLfTbl[subcount], SUBL, CB_NSTAGES);
- /* update memory */
- memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
- memcpy(mem+CB_MEML-SUBL,
- &reverseDecresidual[subframe*SUBL],
- SUBL*sizeof(float));
- memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
- subcount++;
- }
- /* get decoded residual from reversed vector */
- for (i=0; i<SUBL*Nback; i++) {
- decresidual[SUBL*Nback - i - 1] =
- reverseDecresidual[i];
- }
- }
- /* end encoding part */
- /* adjust index */
- index_conv_enc(cb_index);
- /* pack bytes */
- pbytes=bytes;
- pos=0;
- /* loop over the 3 ULP classes */
- for (ulp=0; ulp<3; ulp++) {
- Andersen, et al. Experimental [Page 60]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* LSF */
- for (k=0; k<LSF_NSPLIT*iLBCenc_inst->lpc_n; k++) {
- packsplit(&lsf_i[k], &firstpart, &lsf_i[k],
- iLBCenc_inst->ULP_inst->lsf_bits[k][ulp],
- iLBCenc_inst->ULP_inst->lsf_bits[k][ulp]+
- iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+1]+
- iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], &pos);
- }
- /* Start block info */
- packsplit(&start, &firstpart, &start,
- iLBCenc_inst->ULP_inst->start_bits[ulp],
- iLBCenc_inst->ULP_inst->start_bits[ulp]+
- iLBCenc_inst->ULP_inst->start_bits[ulp+1]+
- iLBCenc_inst->ULP_inst->start_bits[ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->start_bits[ulp], &pos);
- packsplit(&state_first, &firstpart, &state_first,
- iLBCenc_inst->ULP_inst->startfirst_bits[ulp],
- iLBCenc_inst->ULP_inst->startfirst_bits[ulp]+
- iLBCenc_inst->ULP_inst->startfirst_bits[ulp+1]+
- iLBCenc_inst->ULP_inst->startfirst_bits[ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->startfirst_bits[ulp], &pos);
- packsplit(&idxForMax, &firstpart, &idxForMax,
- iLBCenc_inst->ULP_inst->scale_bits[ulp],
- iLBCenc_inst->ULP_inst->scale_bits[ulp]+
- iLBCenc_inst->ULP_inst->scale_bits[ulp+1]+
- iLBCenc_inst->ULP_inst->scale_bits[ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->scale_bits[ulp], &pos);
- for (k=0; k<iLBCenc_inst->state_short_len; k++) {
- packsplit(idxVec+k, &firstpart, idxVec+k,
- iLBCenc_inst->ULP_inst->state_bits[ulp],
- iLBCenc_inst->ULP_inst->state_bits[ulp]+
- iLBCenc_inst->ULP_inst->state_bits[ulp+1]+
- iLBCenc_inst->ULP_inst->state_bits[ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->state_bits[ulp], &pos);
- }
- Andersen, et al. Experimental [Page 61]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* 23/22 (20ms/30ms) sample block */
- for (k=0;k<CB_NSTAGES;k++) {
- packsplit(extra_cb_index+k, &firstpart,
- extra_cb_index+k,
- iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp],
- iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp]+
- iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+1]+
- iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp],
- &pos);
- }
- for (k=0;k<CB_NSTAGES;k++) {
- packsplit(extra_gain_index+k, &firstpart,
- extra_gain_index+k,
- iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp],
- iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp]+
- iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+1]+
- iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp],
- &pos);
- }
- /* The two/four (20ms/30ms) 40 sample sub-blocks */
- for (i=0; i<iLBCenc_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- packsplit(cb_index+i*CB_NSTAGES+k, &firstpart,
- cb_index+i*CB_NSTAGES+k,
- iLBCenc_inst->ULP_inst->cb_index[i][k][ulp],
- iLBCenc_inst->ULP_inst->cb_index[i][k][ulp]+
- iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+1]+
- iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->cb_index[i][k][ulp],
- &pos);
- }
- }
- for (i=0; i<iLBCenc_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- packsplit(gain_index+i*CB_NSTAGES+k, &firstpart,
- gain_index+i*CB_NSTAGES+k,
- iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp],
- iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp]+
- Andersen, et al. Experimental [Page 62]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+1]+
- iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+2]);
- dopack( &pbytes, firstpart,
- iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp],
- &pos);
- }
- }
- }
- /* set the last bit to zero (otherwise the decoder
- will treat it as a lost frame) */
- dopack( &pbytes, 0, 1, &pos);
- }
- A.4. iLBC_decode.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_decode.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_ILBCDECODE_H
- #define __iLBC_ILBCDECODE_H
- #include "iLBC_define.h"
- short initDecode( /* (o) Number of decoded
- samples */
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */
- int mode, /* (i) frame size mode */
- int use_enhancer /* (i) 1 to use enhancer
- 0 to run without
- enhancer */
- );
- void iLBC_decode(
- float *decblock, /* (o) decoded signal block */
- unsigned char *bytes, /* (i) encoded signal bits */
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state
- structure */
- int mode /* (i) 0: bad packet, PLC,
- 1: normal */
- Andersen, et al. Experimental [Page 63]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- );
- #endif
- A.5. iLBC_decode.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_decode.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <stdlib.h>
- #include "iLBC_define.h"
- #include "StateConstructW.h"
- #include "LPCdecode.h"
- #include "iCBConstruct.h"
- #include "doCPLC.h"
- #include "helpfun.h"
- #include "constants.h"
- #include "packing.h"
- #include "string.h"
- #include "enhancer.h"
- #include "hpOutput.h"
- #include "syntFilter.h"
- /*----------------------------------------------------------------*
- * Initiation of decoder instance.
- *---------------------------------------------------------------*/
- short initDecode( /* (o) Number of decoded
- samples */
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */
- int mode, /* (i) frame size mode */
- int use_enhancer /* (i) 1 to use enhancer
- 0 to run without
- enhancer */
- ){
- int i;
- iLBCdec_inst->mode = mode;
- Andersen, et al. Experimental [Page 64]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if (mode==30) {
- iLBCdec_inst->blockl = BLOCKL_30MS;
- iLBCdec_inst->nsub = NSUB_30MS;
- iLBCdec_inst->nasub = NASUB_30MS;
- iLBCdec_inst->lpc_n = LPC_N_30MS;
- iLBCdec_inst->no_of_bytes = NO_OF_BYTES_30MS;
- iLBCdec_inst->no_of_words = NO_OF_WORDS_30MS;
- iLBCdec_inst->state_short_len=STATE_SHORT_LEN_30MS;
- /* ULP init */
- iLBCdec_inst->ULP_inst=&ULP_30msTbl;
- }
- else if (mode==20) {
- iLBCdec_inst->blockl = BLOCKL_20MS;
- iLBCdec_inst->nsub = NSUB_20MS;
- iLBCdec_inst->nasub = NASUB_20MS;
- iLBCdec_inst->lpc_n = LPC_N_20MS;
- iLBCdec_inst->no_of_bytes = NO_OF_BYTES_20MS;
- iLBCdec_inst->no_of_words = NO_OF_WORDS_20MS;
- iLBCdec_inst->state_short_len=STATE_SHORT_LEN_20MS;
- /* ULP init */
- iLBCdec_inst->ULP_inst=&ULP_20msTbl;
- }
- else {
- exit(2);
- }
- memset(iLBCdec_inst->syntMem, 0,
- LPC_FILTERORDER*sizeof(float));
- memcpy((*iLBCdec_inst).lsfdeqold, lsfmeanTbl,
- LPC_FILTERORDER*sizeof(float));
- memset(iLBCdec_inst->old_syntdenum, 0,
- ((LPC_FILTERORDER + 1)*NSUB_MAX)*sizeof(float));
- for (i=0; i<NSUB_MAX; i++)
- iLBCdec_inst->old_syntdenum[i*(LPC_FILTERORDER+1)]=1.0;
- iLBCdec_inst->last_lag = 20;
- iLBCdec_inst->prevLag = 120;
- iLBCdec_inst->per = 0.0;
- iLBCdec_inst->consPLICount = 0;
- iLBCdec_inst->prevPLI = 0;
- iLBCdec_inst->prevLpc[0] = 1.0;
- memset(iLBCdec_inst->prevLpc+1,0,
- LPC_FILTERORDER*sizeof(float));
- memset(iLBCdec_inst->prevResidual, 0, BLOCKL_MAX*sizeof(float));
- iLBCdec_inst->seed=777;
- Andersen, et al. Experimental [Page 65]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- memset(iLBCdec_inst->hpomem, 0, 4*sizeof(float));
- iLBCdec_inst->use_enhancer = use_enhancer;
- memset(iLBCdec_inst->enh_buf, 0, ENH_BUFL*sizeof(float));
- for (i=0;i<ENH_NBLOCKS_TOT;i++)
- iLBCdec_inst->enh_period[i]=(float)40.0;
- iLBCdec_inst->prev_enh_pl = 0;
- return (iLBCdec_inst->blockl);
- }
- /*----------------------------------------------------------------*
- * frame residual decoder function (subrutine to iLBC_decode)
- *---------------------------------------------------------------*/
- void Decode(
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state
- structure */
- float *decresidual, /* (o) decoded residual frame */
- int start, /* (i) location of start
- state */
- int idxForMax, /* (i) codebook index for the
- maximum value */
- int *idxVec, /* (i) codebook indexes for the
- samples in the start
- state */
- float *syntdenum, /* (i) the decoded synthesis
- filter coefficients */
- int *cb_index, /* (i) the indexes for the
- adaptive codebook */
- int *gain_index, /* (i) the indexes for the
- corresponding gains */
- int *extra_cb_index, /* (i) the indexes for the
- adaptive codebook part
- of start state */
- int *extra_gain_index, /* (i) the indexes for the
- corresponding gains */
- int state_first /* (i) 1 if non adaptive part
- of start state comes
- first 0 if that part
- comes last */
- ){
- float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML];
- int k, meml_gotten, Nfor, Nback, i;
- int diff, start_pos;
- int subcount, subframe;
- Andersen, et al. Experimental [Page 66]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- diff = STATE_LEN - iLBCdec_inst->state_short_len;
- if (state_first == 1) {
- start_pos = (start-1)*SUBL;
- } else {
- start_pos = (start-1)*SUBL + diff;
- }
- /* decode scalar part of start state */
- StateConstructW(idxForMax, idxVec,
- &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
- &decresidual[start_pos], iLBCdec_inst->state_short_len);
- if (state_first) { /* put adaptive part in the end */
- /* setup memory */
- memset(mem, 0,
- (CB_MEML-iLBCdec_inst->state_short_len)*sizeof(float));
- memcpy(mem+CB_MEML-iLBCdec_inst->state_short_len,
- decresidual+start_pos,
- iLBCdec_inst->state_short_len*sizeof(float));
- /* construct decoded vector */
- iCBConstruct(
- &decresidual[start_pos+iLBCdec_inst->state_short_len],
- extra_cb_index, extra_gain_index, mem+CB_MEML-stMemLTbl,
- stMemLTbl, diff, CB_NSTAGES);
- }
- else {/* put adaptive part in the beginning */
- /* create reversed vectors for prediction */
- for (k=0; k<diff; k++) {
- reverseDecresidual[k] =
- decresidual[(start+1)*SUBL-1-
- (k+iLBCdec_inst->state_short_len)];
- }
- /* setup memory */
- meml_gotten = iLBCdec_inst->state_short_len;
- for (k=0; k<meml_gotten; k++){
- mem[CB_MEML-1-k] = decresidual[start_pos + k];
- Andersen, et al. Experimental [Page 67]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- memset(mem, 0, (CB_MEML-k)*sizeof(float));
- /* construct decoded vector */
- iCBConstruct(reverseDecresidual, extra_cb_index,
- extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl,
- diff, CB_NSTAGES);
- /* get decoded residual from reversed vector */
- for (k=0; k<diff; k++) {
- decresidual[start_pos-1-k] = reverseDecresidual[k];
- }
- }
- /* counter for predicted sub-frames */
- subcount=0;
- /* forward prediction of sub-frames */
- Nfor = iLBCdec_inst->nsub-start-1;
- if ( Nfor > 0 ){
- /* setup memory */
- memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float));
- memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL,
- STATE_LEN*sizeof(float));
- /* loop over sub-frames to encode */
- for (subframe=0; subframe<Nfor; subframe++) {
- /* construct decoded vector */
- iCBConstruct(&decresidual[(start+1+subframe)*SUBL],
- cb_index+subcount*CB_NSTAGES,
- gain_index+subcount*CB_NSTAGES,
- mem+CB_MEML-memLfTbl[subcount],
- memLfTbl[subcount], SUBL, CB_NSTAGES);
- /* update memory */
- memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
- memcpy(mem+CB_MEML-SUBL,
- Andersen, et al. Experimental [Page 68]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- &decresidual[(start+1+subframe)*SUBL],
- SUBL*sizeof(float));
- subcount++;
- }
- }
- /* backward prediction of sub-frames */
- Nback = start-1;
- if ( Nback > 0 ) {
- /* setup memory */
- meml_gotten = SUBL*(iLBCdec_inst->nsub+1-start);
- if ( meml_gotten > CB_MEML ) {
- meml_gotten=CB_MEML;
- }
- for (k=0; k<meml_gotten; k++) {
- mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k];
- }
- memset(mem, 0, (CB_MEML-k)*sizeof(float));
- /* loop over subframes to decode */
- for (subframe=0; subframe<Nback; subframe++) {
- /* construct decoded vector */
- iCBConstruct(&reverseDecresidual[subframe*SUBL],
- cb_index+subcount*CB_NSTAGES,
- gain_index+subcount*CB_NSTAGES,
- mem+CB_MEML-memLfTbl[subcount], memLfTbl[subcount],
- SUBL, CB_NSTAGES);
- /* update memory */
- memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
- memcpy(mem+CB_MEML-SUBL,
- &reverseDecresidual[subframe*SUBL],
- SUBL*sizeof(float));
- subcount++;
- }
- Andersen, et al. Experimental [Page 69]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* get decoded residual from reversed vector */
- for (i=0; i<SUBL*Nback; i++)
- decresidual[SUBL*Nback - i - 1] =
- reverseDecresidual[i];
- }
- }
- /*----------------------------------------------------------------*
- * main decoder function
- *---------------------------------------------------------------*/
- void iLBC_decode(
- float *decblock, /* (o) decoded signal block */
- unsigned char *bytes, /* (i) encoded signal bits */
- iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state
- structure */
- int mode /* (i) 0: bad packet, PLC,
- 1: normal */
- ){
- float data[BLOCKL_MAX];
- float lsfdeq[LPC_FILTERORDER*LPC_N_MAX];
- float PLCresidual[BLOCKL_MAX], PLClpc[LPC_FILTERORDER + 1];
- float zeros[BLOCKL_MAX], one[LPC_FILTERORDER + 1];
- int k, i, start, idxForMax, pos, lastpart, ulp;
- int lag, ilag;
- float cc, maxcc;
- int idxVec[STATE_LEN];
- int check;
- int gain_index[NASUB_MAX*CB_NSTAGES],
- extra_gain_index[CB_NSTAGES];
- int cb_index[CB_NSTAGES*NASUB_MAX], extra_cb_index[CB_NSTAGES];
- int lsf_i[LSF_NSPLIT*LPC_N_MAX];
- int state_first;
- int last_bit;
- unsigned char *pbytes;
- float weightdenum[(LPC_FILTERORDER + 1)*NSUB_MAX];
- int order_plus_one;
- float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
- float decresidual[BLOCKL_MAX];
- if (mode>0) { /* the data are good */
- /* decode data */
- pbytes=bytes;
- pos=0;
- Andersen, et al. Experimental [Page 70]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* Set everything to zero before decoding */
- for (k=0; k<LSF_NSPLIT*LPC_N_MAX; k++) {
- lsf_i[k]=0;
- }
- start=0;
- state_first=0;
- idxForMax=0;
- for (k=0; k<iLBCdec_inst->state_short_len; k++) {
- idxVec[k]=0;
- }
- for (k=0; k<CB_NSTAGES; k++) {
- extra_cb_index[k]=0;
- }
- for (k=0; k<CB_NSTAGES; k++) {
- extra_gain_index[k]=0;
- }
- for (i=0; i<iLBCdec_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- cb_index[i*CB_NSTAGES+k]=0;
- }
- }
- for (i=0; i<iLBCdec_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- gain_index[i*CB_NSTAGES+k]=0;
- }
- }
- /* loop over ULP classes */
- for (ulp=0; ulp<3; ulp++) {
- /* LSF */
- for (k=0; k<LSF_NSPLIT*iLBCdec_inst->lpc_n; k++){
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->lsf_bits[k][ulp], &pos);
- packcombine(&lsf_i[k], lastpart,
- iLBCdec_inst->ULP_inst->lsf_bits[k][ulp]);
- }
- /* Start block info */
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->start_bits[ulp], &pos);
- packcombine(&start, lastpart,
- iLBCdec_inst->ULP_inst->start_bits[ulp]);
- unpack( &pbytes, &lastpart,
- Andersen, et al. Experimental [Page 71]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- iLBCdec_inst->ULP_inst->startfirst_bits[ulp], &pos);
- packcombine(&state_first, lastpart,
- iLBCdec_inst->ULP_inst->startfirst_bits[ulp]);
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->scale_bits[ulp], &pos);
- packcombine(&idxForMax, lastpart,
- iLBCdec_inst->ULP_inst->scale_bits[ulp]);
- for (k=0; k<iLBCdec_inst->state_short_len; k++) {
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->state_bits[ulp], &pos);
- packcombine(idxVec+k, lastpart,
- iLBCdec_inst->ULP_inst->state_bits[ulp]);
- }
- /* 23/22 (20ms/30ms) sample block */
- for (k=0; k<CB_NSTAGES; k++) {
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp],
- &pos);
- packcombine(extra_cb_index+k, lastpart,
- iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp]);
- }
- for (k=0; k<CB_NSTAGES; k++) {
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp],
- &pos);
- packcombine(extra_gain_index+k, lastpart,
- iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp]);
- }
- /* The two/four (20ms/30ms) 40 sample sub-blocks */
- for (i=0; i<iLBCdec_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- unpack( &pbytes, &lastpart,
- iLBCdec_inst->ULP_inst->cb_index[i][k][ulp],
- &pos);
- packcombine(cb_index+i*CB_NSTAGES+k, lastpart,
- iLBCdec_inst->ULP_inst->cb_index[i][k][ulp]);
- }
- }
- for (i=0; i<iLBCdec_inst->nasub; i++) {
- for (k=0; k<CB_NSTAGES; k++) {
- unpack( &pbytes, &lastpart,
- Andersen, et al. Experimental [Page 72]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp],
- &pos);
- packcombine(gain_index+i*CB_NSTAGES+k, lastpart,
- iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp]);
- }
- }
- }
- /* Extract last bit. If it is 1 this indicates an
- empty/lost frame */
- unpack( &pbytes, &last_bit, 1, &pos);
- /* Check for bit errors or empty/lost frames */
- if (start<1)
- mode = 0;
- if (iLBCdec_inst->mode==20 && start>3)
- mode = 0;
- if (iLBCdec_inst->mode==30 && start>5)
- mode = 0;
- if (last_bit==1)
- mode = 0;
- if (mode==1) { /* No bit errors was detected,
- continue decoding */
- /* adjust index */
- index_conv_dec(cb_index);
- /* decode the lsf */
- SimplelsfDEQ(lsfdeq, lsf_i, iLBCdec_inst->lpc_n);
- check=LSF_check(lsfdeq, LPC_FILTERORDER,
- iLBCdec_inst->lpc_n);
- DecoderInterpolateLSF(syntdenum, weightdenum,
- lsfdeq, LPC_FILTERORDER, iLBCdec_inst);
- Decode(iLBCdec_inst, decresidual, start, idxForMax,
- idxVec, syntdenum, cb_index, gain_index,
- extra_cb_index, extra_gain_index,
- state_first);
- /* preparing the plc for a future loss! */
- doThePLC(PLCresidual, PLClpc, 0, decresidual,
- syntdenum +
- (LPC_FILTERORDER + 1)*(iLBCdec_inst->nsub - 1),
- (*iLBCdec_inst).last_lag, iLBCdec_inst);
- Andersen, et al. Experimental [Page 73]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- memcpy(decresidual, PLCresidual,
- iLBCdec_inst->blockl*sizeof(float));
- }
- }
- if (mode == 0) {
- /* the data is bad (either a PLC call
- * was made or a severe bit error was detected)
- */
- /* packet loss conceal */
- memset(zeros, 0, BLOCKL_MAX*sizeof(float));
- one[0] = 1;
- memset(one+1, 0, LPC_FILTERORDER*sizeof(float));
- start=0;
- doThePLC(PLCresidual, PLClpc, 1, zeros, one,
- (*iLBCdec_inst).last_lag, iLBCdec_inst);
- memcpy(decresidual, PLCresidual,
- iLBCdec_inst->blockl*sizeof(float));
- order_plus_one = LPC_FILTERORDER + 1;
- for (i = 0; i < iLBCdec_inst->nsub; i++) {
- memcpy(syntdenum+(i*order_plus_one), PLClpc,
- order_plus_one*sizeof(float));
- }
- }
- if (iLBCdec_inst->use_enhancer == 1) {
- /* post filtering */
- iLBCdec_inst->last_lag =
- enhancerInterface(data, decresidual, iLBCdec_inst);
- /* synthesis filtering */
- if (iLBCdec_inst->mode==20) {
- /* Enhancer has 40 samples delay */
- i=0;
- syntFilter(data + i*SUBL,
- iLBCdec_inst->old_syntdenum +
- (i+iLBCdec_inst->nsub-1)*(LPC_FILTERORDER+1),
- SUBL, iLBCdec_inst->syntMem);
- Andersen, et al. Experimental [Page 74]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (i=1; i < iLBCdec_inst->nsub; i++) {
- syntFilter(data + i*SUBL,
- syntdenum + (i-1)*(LPC_FILTERORDER+1),
- SUBL, iLBCdec_inst->syntMem);
- }
- } else if (iLBCdec_inst->mode==30) {
- /* Enhancer has 80 samples delay */
- for (i=0; i < 2; i++) {
- syntFilter(data + i*SUBL,
- iLBCdec_inst->old_syntdenum +
- (i+iLBCdec_inst->nsub-2)*(LPC_FILTERORDER+1),
- SUBL, iLBCdec_inst->syntMem);
- }
- for (i=2; i < iLBCdec_inst->nsub; i++) {
- syntFilter(data + i*SUBL,
- syntdenum + (i-2)*(LPC_FILTERORDER+1), SUBL,
- iLBCdec_inst->syntMem);
- }
- }
- } else {
- /* Find last lag */
- lag = 20;
- maxcc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL],
- &decresidual[BLOCKL_MAX-ENH_BLOCKL-lag], ENH_BLOCKL);
- for (ilag=21; ilag<120; ilag++) {
- cc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL],
- &decresidual[BLOCKL_MAX-ENH_BLOCKL-ilag],
- ENH_BLOCKL);
- if (cc > maxcc) {
- maxcc = cc;
- lag = ilag;
- }
- }
- iLBCdec_inst->last_lag = lag;
- /* copy data and run synthesis filter */
- memcpy(data, decresidual,
- iLBCdec_inst->blockl*sizeof(float));
- for (i=0; i < iLBCdec_inst->nsub; i++) {
- syntFilter(data + i*SUBL,
- syntdenum + i*(LPC_FILTERORDER+1), SUBL,
- iLBCdec_inst->syntMem);
- }
- Andersen, et al. Experimental [Page 75]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- /* high pass filtering on output if desired, otherwise
- copy to out */
- hpOutput(data, iLBCdec_inst->blockl,
- decblock,iLBCdec_inst->hpomem);
- /* memcpy(decblock,data,iLBCdec_inst->blockl*sizeof(float));*/
- memcpy(iLBCdec_inst->old_syntdenum, syntdenum,
- iLBCdec_inst->nsub*(LPC_FILTERORDER+1)*sizeof(float));
- iLBCdec_inst->prev_enh_pl=0;
- if (mode==0) { /* PLC was used */
- iLBCdec_inst->prev_enh_pl=1;
- }
- }
- A.6. iLBC_define.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iLBC_define.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <string.h>
- #ifndef __iLBC_ILBCDEFINE_H
- #define __iLBC_ILBCDEFINE_H
- /* general codec settings */
- #define FS (float)8000.0
- #define BLOCKL_20MS 160
- #define BLOCKL_30MS 240
- #define BLOCKL_MAX 240
- #define NSUB_20MS 4
- #define NSUB_30MS 6
- #define NSUB_MAX 6
- #define NASUB_20MS 2
- Andersen, et al. Experimental [Page 76]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #define NASUB_30MS 4
- #define NASUB_MAX 4
- #define SUBL 40
- #define STATE_LEN 80
- #define STATE_SHORT_LEN_30MS 58
- #define STATE_SHORT_LEN_20MS 57
- /* LPC settings */
- #define LPC_FILTERORDER 10
- #define LPC_CHIRP_SYNTDENUM (float)0.9025
- #define LPC_CHIRP_WEIGHTDENUM (float)0.4222
- #define LPC_LOOKBACK 60
- #define LPC_N_20MS 1
- #define LPC_N_30MS 2
- #define LPC_N_MAX 2
- #define LPC_ASYMDIFF 20
- #define LPC_BW (float)60.0
- #define LPC_WN (float)1.0001
- #define LSF_NSPLIT 3
- #define LSF_NUMBER_OF_STEPS 4
- #define LPC_HALFORDER (LPC_FILTERORDER/2)
- /* cb settings */
- #define CB_NSTAGES 3
- #define CB_EXPAND 2
- #define CB_MEML 147
- #define CB_FILTERLEN 2*4
- #define CB_HALFFILTERLEN 4
- #define CB_RESRANGE 34
- #define CB_MAXGAIN (float)1.3
- /* enhancer */
- #define ENH_BLOCKL 80 /* block length */
- #define ENH_BLOCKL_HALF (ENH_BLOCKL/2)
- #define ENH_HL 3 /* 2*ENH_HL+1 is number blocks
- in said second sequence */
- #define ENH_SLOP 2 /* max difference estimated and
- correct pitch period */
- #define ENH_PLOCSL 20 /* pitch-estimates and pitch-
- locations buffer length */
- #define ENH_OVERHANG 2
- #define ENH_UPS0 4 /* upsampling rate */
- #define ENH_FL0 3 /* 2*FLO+1 is the length of
- each filter */
- #define ENH_VECTL (ENH_BLOCKL+2*ENH_FL0)
- Andersen, et al. Experimental [Page 77]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #define ENH_CORRDIM (2*ENH_SLOP+1)
- #define ENH_NBLOCKS (BLOCKL_MAX/ENH_BLOCKL)
- #define ENH_NBLOCKS_EXTRA 5
- #define ENH_NBLOCKS_TOT 8 /* ENH_NBLOCKS +
- ENH_NBLOCKS_EXTRA */
- #define ENH_BUFL (ENH_NBLOCKS_TOT)*ENH_BLOCKL
- #define ENH_ALPHA0 (float)0.05
- /* Down sampling */
- #define FILTERORDER_DS 7
- #define DELAY_DS 3
- #define FACTOR_DS 2
- /* bit stream defs */
- #define NO_OF_BYTES_20MS 38
- #define NO_OF_BYTES_30MS 50
- #define NO_OF_WORDS_20MS 19
- #define NO_OF_WORDS_30MS 25
- #define STATE_BITS 3
- #define BYTE_LEN 8
- #define ULP_CLASSES 3
- /* help parameters */
- #define FLOAT_MAX (float)1.0e37
- #define EPS (float)2.220446049250313e-016
- #define PI (float)3.14159265358979323846
- #define MIN_SAMPLE -32768
- #define MAX_SAMPLE 32767
- #define TWO_PI (float)6.283185307
- #define PI2 (float)0.159154943
- /* type definition encoder instance */
- typedef struct iLBC_ULP_Inst_t_ {
- int lsf_bits[6][ULP_CLASSES+2];
- int start_bits[ULP_CLASSES+2];
- int startfirst_bits[ULP_CLASSES+2];
- int scale_bits[ULP_CLASSES+2];
- int state_bits[ULP_CLASSES+2];
- int extra_cb_index[CB_NSTAGES][ULP_CLASSES+2];
- int extra_cb_gain[CB_NSTAGES][ULP_CLASSES+2];
- int cb_index[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2];
- int cb_gain[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2];
- } iLBC_ULP_Inst_t;
- /* type definition encoder instance */
- Andersen, et al. Experimental [Page 78]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- typedef struct iLBC_Enc_Inst_t_ {
- /* flag for frame size mode */
- int mode;
- /* basic parameters for different frame sizes */
- int blockl;
- int nsub;
- int nasub;
- int no_of_bytes, no_of_words;
- int lpc_n;
- int state_short_len;
- const iLBC_ULP_Inst_t *ULP_inst;
- /* analysis filter state */
- float anaMem[LPC_FILTERORDER];
- /* old lsf parameters for interpolation */
- float lsfold[LPC_FILTERORDER];
- float lsfdeqold[LPC_FILTERORDER];
- /* signal buffer for LP analysis */
- float lpc_buffer[LPC_LOOKBACK + BLOCKL_MAX];
- /* state of input HP filter */
- float hpimem[4];
- } iLBC_Enc_Inst_t;
- /* type definition decoder instance */
- typedef struct iLBC_Dec_Inst_t_ {
- /* flag for frame size mode */
- int mode;
- /* basic parameters for different frame sizes */
- int blockl;
- int nsub;
- int nasub;
- int no_of_bytes, no_of_words;
- int lpc_n;
- int state_short_len;
- const iLBC_ULP_Inst_t *ULP_inst;
- /* synthesis filter state */
- float syntMem[LPC_FILTERORDER];
- /* old LSF for interpolation */
- Andersen, et al. Experimental [Page 79]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float lsfdeqold[LPC_FILTERORDER];
- /* pitch lag estimated in enhancer and used in PLC */
- int last_lag;
- /* PLC state information */
- int prevLag, consPLICount, prevPLI, prev_enh_pl;
- float prevLpc[LPC_FILTERORDER+1];
- float prevResidual[NSUB_MAX*SUBL];
- float per;
- unsigned long seed;
- /* previous synthesis filter parameters */
- float old_syntdenum[(LPC_FILTERORDER + 1)*NSUB_MAX];
- /* state of output HP filter */
- float hpomem[4];
- /* enhancer state information */
- int use_enhancer;
- float enh_buf[ENH_BUFL];
- float enh_period[ENH_NBLOCKS_TOT];
- } iLBC_Dec_Inst_t;
- #endif
- A.7. constants.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- constants.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_CONSTANTS_H
- #define __iLBC_CONSTANTS_H
- #include "iLBC_define.h"
- /* ULP bit allocation */
- Andersen, et al. Experimental [Page 80]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- extern const iLBC_ULP_Inst_t ULP_20msTbl;
- extern const iLBC_ULP_Inst_t ULP_30msTbl;
- /* high pass filters */
- extern float hpi_zero_coefsTbl[];
- extern float hpi_pole_coefsTbl[];
- extern float hpo_zero_coefsTbl[];
- extern float hpo_pole_coefsTbl[];
- /* low pass filters */
- extern float lpFilt_coefsTbl[];
- /* LPC analysis and quantization */
- extern float lpc_winTbl[];
- extern float lpc_asymwinTbl[];
- extern float lpc_lagwinTbl[];
- extern float lsfCbTbl[];
- extern float lsfmeanTbl[];
- extern int dim_lsfCbTbl[];
- extern int size_lsfCbTbl[];
- extern float lsf_weightTbl_30ms[];
- extern float lsf_weightTbl_20ms[];
- /* state quantization tables */
- extern float state_sq3Tbl[];
- extern float state_frgqTbl[];
- /* gain quantization tables */
- extern float gain_sq3Tbl[];
- extern float gain_sq4Tbl[];
- extern float gain_sq5Tbl[];
- /* adaptive codebook definitions */
- extern int search_rangeTbl[5][CB_NSTAGES];
- extern int memLfTbl[];
- extern int stMemLTbl;
- extern float cbfiltersTbl[CB_FILTERLEN];
- /* enhancer definitions */
- extern float polyphaserTbl[];
- extern float enh_plocsTbl[];
- Andersen, et al. Experimental [Page 81]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #endif
- A.8. constants.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- constants.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "iLBC_define.h"
- /* ULP bit allocation */
- /* 20 ms frame */
- const iLBC_ULP_Inst_t ULP_20msTbl = {
- /* LSF */
- { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0},
- {0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
- /* Start state location, gain and samples */
- {2,0,0,0,0},
- {1,0,0,0,0},
- {6,0,0,0,0},
- {0,1,2,0,0},
- /* extra CB index and extra CB gain */
- {{6,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
- {{2,0,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
- /* CB index and CB gain */
- { {{7,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
- {{0,0,8,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
- {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
- {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}},
- { {{1,2,2,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
- {{1,1,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}},
- {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
- {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}}
- };
- /* 30 ms frame */
- const iLBC_ULP_Inst_t ULP_30msTbl = {
- /* LSF */
- Andersen, et al. Experimental [Page 82]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0},
- {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}},
- /* Start state location, gain and samples */
- {3,0,0,0,0},
- {1,0,0,0,0},
- {6,0,0,0,0},
- {0,1,2,0,0},
- /* extra CB index and extra CB gain */
- {{4,2,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
- {{1,1,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
- /* CB index and CB gain */
- { {{6,1,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
- {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
- {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
- {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}},
- { {{1,2,2,0,0}, {1,2,1,0,0}, {0,0,3,0,0}},
- {{0,2,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}},
- {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}},
- {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}}
- };
- /* HP Filters */
- float hpi_zero_coefsTbl[3] = {
- (float)0.92727436, (float)-1.8544941, (float)0.92727436
- };
- float hpi_pole_coefsTbl[3] = {
- (float)1.0, (float)-1.9059465, (float)0.9114024
- };
- float hpo_zero_coefsTbl[3] = {
- (float)0.93980581, (float)-1.8795834, (float)0.93980581
- };
- float hpo_pole_coefsTbl[3] = {
- (float)1.0, (float)-1.9330735, (float)0.93589199
- };
- /* LP Filter */
- float lpFilt_coefsTbl[FILTERORDER_DS]={
- (float)-0.066650, (float)0.125000, (float)0.316650,
- (float)0.414063, (float)0.316650,
- (float)0.125000, (float)-0.066650
- };
- /* State quantization tables */
- float state_sq3Tbl[8] = {
- (float)-3.719849, (float)-2.177490, (float)-1.130005,
- Andersen, et al. Experimental [Page 83]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)-0.309692, (float)0.444214, (float)1.329712,
- (float)2.436279, (float)3.983887
- };
- float state_frgqTbl[64] = {
- (float)1.000085, (float)1.071695, (float)1.140395,
- (float)1.206868, (float)1.277188, (float)1.351503,
- (float)1.429380, (float)1.500727, (float)1.569049,
- (float)1.639599, (float)1.707071, (float)1.781531,
- (float)1.840799, (float)1.901550, (float)1.956695,
- (float)2.006750, (float)2.055474, (float)2.102787,
- (float)2.142819, (float)2.183592, (float)2.217962,
- (float)2.257177, (float)2.295739, (float)2.332967,
- (float)2.369248, (float)2.402792, (float)2.435080,
- (float)2.468598, (float)2.503394, (float)2.539284,
- (float)2.572944, (float)2.605036, (float)2.636331,
- (float)2.668939, (float)2.698780, (float)2.729101,
- (float)2.759786, (float)2.789834, (float)2.818679,
- (float)2.848074, (float)2.877470, (float)2.906899,
- (float)2.936655, (float)2.967804, (float)3.000115,
- (float)3.033367, (float)3.066355, (float)3.104231,
- (float)3.141499, (float)3.183012, (float)3.222952,
- (float)3.265433, (float)3.308441, (float)3.350823,
- (float)3.395275, (float)3.442793, (float)3.490801,
- (float)3.542514, (float)3.604064, (float)3.666050,
- (float)3.740994, (float)3.830749, (float)3.938770,
- (float)4.101764
- };
- /* CB tables */
- int search_rangeTbl[5][CB_NSTAGES]={{58,58,58}, {108,44,44},
- {108,108,108}, {108,108,108}, {108,108,108}};
- int stMemLTbl=85;
- int memLfTbl[NASUB_MAX]={147,147,147,147};
- /* expansion filter(s) */
- float cbfiltersTbl[CB_FILTERLEN]={
- (float)-0.034180, (float)0.108887, (float)-0.184326,
- (float)0.806152, (float)0.713379, (float)-0.144043,
- (float)0.083740, (float)-0.033691
- };
- /* Gain Quantization */
- float gain_sq3Tbl[8]={
- (float)-1.000000, (float)-0.659973, (float)-0.330017,
- Andersen, et al. Experimental [Page 84]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.000000, (float)0.250000, (float)0.500000,
- (float)0.750000, (float)1.00000};
- float gain_sq4Tbl[16]={
- (float)-1.049988, (float)-0.900024, (float)-0.750000,
- (float)-0.599976, (float)-0.450012, (float)-0.299988,
- (float)-0.150024, (float)0.000000, (float)0.150024,
- (float)0.299988, (float)0.450012, (float)0.599976,
- (float)0.750000, (float)0.900024, (float)1.049988,
- (float)1.200012};
- float gain_sq5Tbl[32]={
- (float)0.037476, (float)0.075012, (float)0.112488,
- (float)0.150024, (float)0.187500, (float)0.224976,
- (float)0.262512, (float)0.299988, (float)0.337524,
- (float)0.375000, (float)0.412476, (float)0.450012,
- (float)0.487488, (float)0.525024, (float)0.562500,
- (float)0.599976, (float)0.637512, (float)0.674988,
- (float)0.712524, (float)0.750000, (float)0.787476,
- (float)0.825012, (float)0.862488, (float)0.900024,
- (float)0.937500, (float)0.974976, (float)1.012512,
- (float)1.049988, (float)1.087524, (float)1.125000,
- (float)1.162476, (float)1.200012};
- /* Enhancer - Upsamling a factor 4 (ENH_UPS0 = 4) */
- float polyphaserTbl[ENH_UPS0*(2*ENH_FL0+1)]={
- (float)0.000000, (float)0.000000, (float)0.000000,
- (float)1.000000,
- (float)0.000000, (float)0.000000, (float)0.000000,
- (float)0.015625, (float)-0.076904, (float)0.288330,
- (float)0.862061,
- (float)-0.106445, (float)0.018799, (float)-0.015625,
- (float)0.023682, (float)-0.124268, (float)0.601563,
- (float)0.601563,
- (float)-0.124268, (float)0.023682, (float)-0.023682,
- (float)0.018799, (float)-0.106445, (float)0.862061,
- (float)0.288330,
- (float)-0.076904, (float)0.015625, (float)-0.018799};
- float enh_plocsTbl[ENH_NBLOCKS_TOT] = {(float)40.0, (float)120.0,
- (float)200.0, (float)280.0, (float)360.0,
- (float)440.0, (float)520.0, (float)600.0};
- /* LPC analysis and quantization */
- int dim_lsfCbTbl[LSF_NSPLIT] = {3, 3, 4};
- int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128};
- Andersen, et al. Experimental [Page 85]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float lsfmeanTbl[LPC_FILTERORDER] = {
- (float)0.281738, (float)0.445801, (float)0.663330,
- (float)0.962524, (float)1.251831, (float)1.533081,
- (float)1.850586, (float)2.137817, (float)2.481445,
- (float)2.777344};
- float lsf_weightTbl_30ms[6] = {(float)(1.0/2.0), (float)1.0,
- (float)(2.0/3.0),
- (float)(1.0/3.0), (float)0.0, (float)0.0};
- float lsf_weightTbl_20ms[4] = {(float)(3.0/4.0), (float)(2.0/4.0),
- (float)(1.0/4.0), (float)(0.0)};
- /* Hanning LPC window */
- float lpc_winTbl[BLOCKL_MAX]={
- (float)0.000183, (float)0.000671, (float)0.001526,
- (float)0.002716, (float)0.004242, (float)0.006104,
- (float)0.008301, (float)0.010834, (float)0.013702,
- (float)0.016907, (float)0.020416, (float)0.024261,
- (float)0.028442, (float)0.032928, (float)0.037750,
- (float)0.042877, (float)0.048309, (float)0.054047,
- (float)0.060089, (float)0.066437, (float)0.073090,
- (float)0.080017, (float)0.087219, (float)0.094727,
- (float)0.102509, (float)0.110535, (float)0.118835,
- (float)0.127411, (float)0.136230, (float)0.145294,
- (float)0.154602, (float)0.164154, (float)0.173920,
- (float)0.183899, (float)0.194122, (float)0.204529,
- (float)0.215149, (float)0.225952, (float)0.236938,
- (float)0.248108, (float)0.259460, (float)0.270966,
- (float)0.282654, (float)0.294464, (float)0.306396,
- (float)0.318481, (float)0.330688, (float)0.343018,
- (float)0.355438, (float)0.367981, (float)0.380585,
- (float)0.393280, (float)0.406067, (float)0.418884,
- (float)0.431763, (float)0.444702, (float)0.457672,
- (float)0.470673, (float)0.483704, (float)0.496735,
- (float)0.509766, (float)0.522797, (float)0.535828,
- (float)0.548798, (float)0.561768, (float)0.574677,
- (float)0.587524, (float)0.600342, (float)0.613068,
- (float)0.625732, (float)0.638306, (float)0.650787,
- (float)0.663147, (float)0.675415, (float)0.687561,
- (float)0.699585, (float)0.711487, (float)0.723206,
- (float)0.734802, (float)0.746216, (float)0.757477,
- (float)0.768585, (float)0.779480, (float)0.790192,
- (float)0.800720, (float)0.811005, (float)0.821106,
- (float)0.830994, (float)0.840668, (float)0.850067,
- (float)0.859253, (float)0.868225, (float)0.876892,
- (float)0.885345, (float)0.893524, (float)0.901428,
- (float)0.909058, (float)0.916412, (float)0.923492,
- Andersen, et al. Experimental [Page 86]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.930267, (float)0.936768, (float)0.942963,
- (float)0.948853, (float)0.954437, (float)0.959717,
- (float)0.964691, (float)0.969360, (float)0.973694,
- (float)0.977692, (float)0.981384, (float)0.984741,
- (float)0.987762, (float)0.990479, (float)0.992828,
- (float)0.994873, (float)0.996552, (float)0.997925,
- (float)0.998932, (float)0.999603, (float)0.999969,
- (float)0.999969, (float)0.999603, (float)0.998932,
- (float)0.997925, (float)0.996552, (float)0.994873,
- (float)0.992828, (float)0.990479, (float)0.987762,
- (float)0.984741, (float)0.981384, (float)0.977692,
- (float)0.973694, (float)0.969360, (float)0.964691,
- (float)0.959717, (float)0.954437, (float)0.948853,
- (float)0.942963, (float)0.936768, (float)0.930267,
- (float)0.923492, (float)0.916412, (float)0.909058,
- (float)0.901428, (float)0.893524, (float)0.885345,
- (float)0.876892, (float)0.868225, (float)0.859253,
- (float)0.850067, (float)0.840668, (float)0.830994,
- (float)0.821106, (float)0.811005, (float)0.800720,
- (float)0.790192, (float)0.779480, (float)0.768585,
- (float)0.757477, (float)0.746216, (float)0.734802,
- (float)0.723206, (float)0.711487, (float)0.699585,
- (float)0.687561, (float)0.675415, (float)0.663147,
- (float)0.650787, (float)0.638306, (float)0.625732,
- (float)0.613068, (float)0.600342, (float)0.587524,
- (float)0.574677, (float)0.561768, (float)0.548798,
- (float)0.535828, (float)0.522797, (float)0.509766,
- (float)0.496735, (float)0.483704, (float)0.470673,
- (float)0.457672, (float)0.444702, (float)0.431763,
- (float)0.418884, (float)0.406067, (float)0.393280,
- (float)0.380585, (float)0.367981, (float)0.355438,
- (float)0.343018, (float)0.330688, (float)0.318481,
- (float)0.306396, (float)0.294464, (float)0.282654,
- (float)0.270966, (float)0.259460, (float)0.248108,
- (float)0.236938, (float)0.225952, (float)0.215149,
- (float)0.204529, (float)0.194122, (float)0.183899,
- (float)0.173920, (float)0.164154, (float)0.154602,
- (float)0.145294, (float)0.136230, (float)0.127411,
- (float)0.118835, (float)0.110535, (float)0.102509,
- (float)0.094727, (float)0.087219, (float)0.080017,
- (float)0.073090, (float)0.066437, (float)0.060089,
- (float)0.054047, (float)0.048309, (float)0.042877,
- (float)0.037750, (float)0.032928, (float)0.028442,
- (float)0.024261, (float)0.020416, (float)0.016907,
- (float)0.013702, (float)0.010834, (float)0.008301,
- (float)0.006104, (float)0.004242, (float)0.002716,
- (float)0.001526, (float)0.000671, (float)0.000183
- };
- Andersen, et al. Experimental [Page 87]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* Asymmetric LPC window */
- float lpc_asymwinTbl[BLOCKL_MAX]={
- (float)0.000061, (float)0.000214, (float)0.000458,
- (float)0.000824, (float)0.001282, (float)0.001831,
- (float)0.002472, (float)0.003235, (float)0.004120,
- (float)0.005066, (float)0.006134, (float)0.007294,
- (float)0.008545, (float)0.009918, (float)0.011383,
- (float)0.012939, (float)0.014587, (float)0.016357,
- (float)0.018219, (float)0.020172, (float)0.022217,
- (float)0.024353, (float)0.026611, (float)0.028961,
- (float)0.031372, (float)0.033905, (float)0.036530,
- (float)0.039276, (float)0.042084, (float)0.044983,
- (float)0.047974, (float)0.051086, (float)0.054260,
- (float)0.057526, (float)0.060883, (float)0.064331,
- (float)0.067871, (float)0.071503, (float)0.075226,
- (float)0.079010, (float)0.082916, (float)0.086884,
- (float)0.090942, (float)0.095062, (float)0.099304,
- (float)0.103607, (float)0.107971, (float)0.112427,
- (float)0.116974, (float)0.121582, (float)0.126282,
- (float)0.131073, (float)0.135895, (float)0.140839,
- (float)0.145813, (float)0.150879, (float)0.156006,
- (float)0.161224, (float)0.166504, (float)0.171844,
- (float)0.177246, (float)0.182709, (float)0.188263,
- (float)0.193848, (float)0.199524, (float)0.205231,
- (float)0.211029, (float)0.216858, (float)0.222778,
- (float)0.228729, (float)0.234741, (float)0.240814,
- (float)0.246918, (float)0.253082, (float)0.259308,
- (float)0.265564, (float)0.271881, (float)0.278259,
- (float)0.284668, (float)0.291107, (float)0.297607,
- (float)0.304138, (float)0.310730, (float)0.317322,
- (float)0.323975, (float)0.330658, (float)0.337372,
- (float)0.344147, (float)0.350922, (float)0.357727,
- (float)0.364594, (float)0.371460, (float)0.378357,
- (float)0.385284, (float)0.392212, (float)0.399170,
- (float)0.406158, (float)0.413177, (float)0.420197,
- (float)0.427246, (float)0.434296, (float)0.441376,
- (float)0.448456, (float)0.455536, (float)0.462646,
- (float)0.469757, (float)0.476868, (float)0.483978,
- (float)0.491089, (float)0.498230, (float)0.505341,
- (float)0.512451, (float)0.519592, (float)0.526703,
- (float)0.533813, (float)0.540924, (float)0.548004,
- (float)0.555084, (float)0.562164, (float)0.569244,
- (float)0.576294, (float)0.583313, (float)0.590332,
- (float)0.597321, (float)0.604309, (float)0.611267,
- (float)0.618195, (float)0.625092, (float)0.631989,
- (float)0.638855, (float)0.645660, (float)0.652466,
- (float)0.659241, (float)0.665985, (float)0.672668,
- (float)0.679352, (float)0.685974, (float)0.692566,
- Andersen, et al. Experimental [Page 88]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.699127, (float)0.705658, (float)0.712128,
- (float)0.718536, (float)0.724945, (float)0.731262,
- (float)0.737549, (float)0.743805, (float)0.750000,
- (float)0.756134, (float)0.762238, (float)0.768280,
- (float)0.774261, (float)0.780182, (float)0.786072,
- (float)0.791870, (float)0.797638, (float)0.803314,
- (float)0.808960, (float)0.814514, (float)0.820038,
- (float)0.825470, (float)0.830841, (float)0.836151,
- (float)0.841400, (float)0.846558, (float)0.851654,
- (float)0.856689, (float)0.861633, (float)0.866516,
- (float)0.871338, (float)0.876068, (float)0.880737,
- (float)0.885315, (float)0.889801, (float)0.894226,
- (float)0.898560, (float)0.902832, (float)0.907013,
- (float)0.911102, (float)0.915100, (float)0.919037,
- (float)0.922882, (float)0.926636, (float)0.930328,
- (float)0.933899, (float)0.937408, (float)0.940796,
- (float)0.944122, (float)0.947357, (float)0.950470,
- (float)0.953522, (float)0.956482, (float)0.959351,
- (float)0.962097, (float)0.964783, (float)0.967377,
- (float)0.969849, (float)0.972229, (float)0.974518,
- (float)0.976715, (float)0.978821, (float)0.980835,
- (float)0.982727, (float)0.984528, (float)0.986237,
- (float)0.987854, (float)0.989380, (float)0.990784,
- (float)0.992096, (float)0.993317, (float)0.994415,
- (float)0.995422, (float)0.996338, (float)0.997162,
- (float)0.997864, (float)0.998474, (float)0.998962,
- (float)0.999390, (float)0.999695, (float)0.999878,
- (float)0.999969, (float)0.999969, (float)0.996918,
- (float)0.987701, (float)0.972382, (float)0.951050,
- (float)0.923889, (float)0.891022, (float)0.852631,
- (float)0.809021, (float)0.760406, (float)0.707092,
- (float)0.649445, (float)0.587799, (float)0.522491,
- (float)0.453979, (float)0.382690, (float)0.309021,
- (float)0.233459, (float)0.156433, (float)0.078461
- };
- /* Lag window for LPC */
- float lpc_lagwinTbl[LPC_FILTERORDER + 1]={
- (float)1.000100, (float)0.998890, (float)0.995569,
- (float)0.990057, (float)0.982392,
- (float)0.972623, (float)0.960816, (float)0.947047,
- (float)0.931405, (float)0.913989, (float)0.894909};
- /* LSF quantization*/
- float lsfCbTbl[64 * 3 + 128 * 3 + 128 * 4] = {
- (float)0.155396, (float)0.273193, (float)0.451172,
- (float)0.390503, (float)0.648071, (float)1.002075,
- (float)0.440186, (float)0.692261, (float)0.955688,
- Andersen, et al. Experimental [Page 89]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.343628, (float)0.642334, (float)1.071533,
- (float)0.318359, (float)0.491577, (float)0.670532,
- (float)0.193115, (float)0.375488, (float)0.725708,
- (float)0.364136, (float)0.510376, (float)0.658691,
- (float)0.297485, (float)0.527588, (float)0.842529,
- (float)0.227173, (float)0.365967, (float)0.563110,
- (float)0.244995, (float)0.396729, (float)0.636475,
- (float)0.169434, (float)0.300171, (float)0.520264,
- (float)0.312866, (float)0.464478, (float)0.643188,
- (float)0.248535, (float)0.429932, (float)0.626099,
- (float)0.236206, (float)0.491333, (float)0.817139,
- (float)0.334961, (float)0.625122, (float)0.895752,
- (float)0.343018, (float)0.518555, (float)0.698608,
- (float)0.372803, (float)0.659790, (float)0.945435,
- (float)0.176880, (float)0.316528, (float)0.581421,
- (float)0.416382, (float)0.625977, (float)0.805176,
- (float)0.303223, (float)0.568726, (float)0.915039,
- (float)0.203613, (float)0.351440, (float)0.588135,
- (float)0.221191, (float)0.375000, (float)0.614746,
- (float)0.199951, (float)0.323364, (float)0.476074,
- (float)0.300781, (float)0.433350, (float)0.566895,
- (float)0.226196, (float)0.354004, (float)0.507568,
- (float)0.300049, (float)0.508179, (float)0.711670,
- (float)0.312012, (float)0.492676, (float)0.763428,
- (float)0.329956, (float)0.541016, (float)0.795776,
- (float)0.373779, (float)0.604614, (float)0.928833,
- (float)0.210571, (float)0.452026, (float)0.755249,
- (float)0.271118, (float)0.473267, (float)0.662476,
- (float)0.285522, (float)0.436890, (float)0.634399,
- (float)0.246704, (float)0.565552, (float)0.859009,
- (float)0.270508, (float)0.406250, (float)0.553589,
- (float)0.361450, (float)0.578491, (float)0.813843,
- (float)0.342651, (float)0.482788, (float)0.622437,
- (float)0.340332, (float)0.549438, (float)0.743164,
- (float)0.200439, (float)0.336304, (float)0.540894,
- (float)0.407837, (float)0.644775, (float)0.895142,
- (float)0.294678, (float)0.454834, (float)0.699097,
- (float)0.193115, (float)0.344482, (float)0.643188,
- (float)0.275757, (float)0.420776, (float)0.598755,
- (float)0.380493, (float)0.608643, (float)0.861084,
- (float)0.222778, (float)0.426147, (float)0.676514,
- (float)0.407471, (float)0.700195, (float)1.053101,
- (float)0.218384, (float)0.377197, (float)0.669922,
- (float)0.313232, (float)0.454102, (float)0.600952,
- (float)0.347412, (float)0.571533, (float)0.874146,
- (float)0.238037, (float)0.405396, (float)0.729492,
- (float)0.223877, (float)0.412964, (float)0.822021,
- (float)0.395264, (float)0.582153, (float)0.743896,
- Andersen, et al. Experimental [Page 90]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.247925, (float)0.485596, (float)0.720581,
- (float)0.229126, (float)0.496582, (float)0.907715,
- (float)0.260132, (float)0.566895, (float)1.012695,
- (float)0.337402, (float)0.611572, (float)0.978149,
- (float)0.267822, (float)0.447632, (float)0.769287,
- (float)0.250610, (float)0.381714, (float)0.530029,
- (float)0.430054, (float)0.805054, (float)1.221924,
- (float)0.382568, (float)0.544067, (float)0.701660,
- (float)0.383545, (float)0.710327, (float)1.149170,
- (float)0.271362, (float)0.529053, (float)0.775513,
- (float)0.246826, (float)0.393555, (float)0.588623,
- (float)0.266846, (float)0.422119, (float)0.676758,
- (float)0.311523, (float)0.580688, (float)0.838623,
- (float)1.331177, (float)1.576782, (float)1.779541,
- (float)1.160034, (float)1.401978, (float)1.768188,
- (float)1.161865, (float)1.525146, (float)1.715332,
- (float)0.759521, (float)0.913940, (float)1.119873,
- (float)0.947144, (float)1.121338, (float)1.282471,
- (float)1.015015, (float)1.557007, (float)1.804932,
- (float)1.172974, (float)1.402100, (float)1.692627,
- (float)1.087524, (float)1.474243, (float)1.665405,
- (float)0.899536, (float)1.105225, (float)1.406250,
- (float)1.148438, (float)1.484741, (float)1.796265,
- (float)0.785645, (float)1.209839, (float)1.567749,
- (float)0.867798, (float)1.166504, (float)1.450684,
- (float)0.922485, (float)1.229858, (float)1.420898,
- (float)0.791260, (float)1.123291, (float)1.409546,
- (float)0.788940, (float)0.966064, (float)1.340332,
- (float)1.051147, (float)1.272827, (float)1.556641,
- (float)0.866821, (float)1.181152, (float)1.538818,
- (float)0.906738, (float)1.373535, (float)1.607910,
- (float)1.244751, (float)1.581421, (float)1.933838,
- (float)0.913940, (float)1.337280, (float)1.539673,
- (float)0.680542, (float)0.959229, (float)1.662720,
- (float)0.887207, (float)1.430542, (float)1.800781,
- (float)0.912598, (float)1.433594, (float)1.683960,
- (float)0.860474, (float)1.060303, (float)1.455322,
- (float)1.005127, (float)1.381104, (float)1.706909,
- (float)0.800781, (float)1.363892, (float)1.829102,
- (float)0.781860, (float)1.124390, (float)1.505981,
- (float)1.003662, (float)1.471436, (float)1.684692,
- (float)0.981323, (float)1.309570, (float)1.618042,
- (float)1.228760, (float)1.554321, (float)1.756470,
- (float)0.734375, (float)0.895752, (float)1.225586,
- (float)0.841797, (float)1.055664, (float)1.249268,
- (float)0.920166, (float)1.119385, (float)1.486206,
- (float)0.894409, (float)1.539063, (float)1.828979,
- (float)1.283691, (float)1.543335, (float)1.858276,
- Andersen, et al. Experimental [Page 91]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.676025, (float)0.933105, (float)1.490845,
- (float)0.821289, (float)1.491821, (float)1.739868,
- (float)0.923218, (float)1.144653, (float)1.580566,
- (float)1.057251, (float)1.345581, (float)1.635864,
- (float)0.888672, (float)1.074951, (float)1.353149,
- (float)0.942749, (float)1.195435, (float)1.505493,
- (float)1.492310, (float)1.788086, (float)2.039673,
- (float)1.070313, (float)1.634399, (float)1.860962,
- (float)1.253296, (float)1.488892, (float)1.686035,
- (float)0.647095, (float)0.864014, (float)1.401855,
- (float)0.866699, (float)1.254883, (float)1.453369,
- (float)1.063965, (float)1.532593, (float)1.731323,
- (float)1.167847, (float)1.521484, (float)1.884033,
- (float)0.956055, (float)1.502075, (float)1.745605,
- (float)0.928711, (float)1.288574, (float)1.479614,
- (float)1.088013, (float)1.380737, (float)1.570801,
- (float)0.905029, (float)1.186768, (float)1.371948,
- (float)1.057861, (float)1.421021, (float)1.617432,
- (float)1.108276, (float)1.312500, (float)1.501465,
- (float)0.979492, (float)1.416992, (float)1.624268,
- (float)1.276001, (float)1.661011, (float)2.007935,
- (float)0.993042, (float)1.168579, (float)1.331665,
- (float)0.778198, (float)0.944946, (float)1.235962,
- (float)1.223755, (float)1.491333, (float)1.815674,
- (float)0.852661, (float)1.350464, (float)1.722290,
- (float)1.134766, (float)1.593140, (float)1.787354,
- (float)1.051392, (float)1.339722, (float)1.531006,
- (float)0.803589, (float)1.271240, (float)1.652100,
- (float)0.755737, (float)1.143555, (float)1.639404,
- (float)0.700928, (float)0.837280, (float)1.130371,
- (float)0.942749, (float)1.197876, (float)1.669800,
- (float)0.993286, (float)1.378296, (float)1.566528,
- (float)0.801025, (float)1.095337, (float)1.298950,
- (float)0.739990, (float)1.032959, (float)1.383667,
- (float)0.845703, (float)1.072266, (float)1.543823,
- (float)0.915649, (float)1.072266, (float)1.224487,
- (float)1.021973, (float)1.226196, (float)1.481323,
- (float)0.999878, (float)1.204102, (float)1.555908,
- (float)0.722290, (float)0.913940, (float)1.340210,
- (float)0.673340, (float)0.835938, (float)1.259521,
- (float)0.832397, (float)1.208374, (float)1.394165,
- (float)0.962158, (float)1.576172, (float)1.912842,
- (float)1.166748, (float)1.370850, (float)1.556763,
- (float)0.946289, (float)1.138550, (float)1.400391,
- (float)1.035034, (float)1.218262, (float)1.386475,
- (float)1.393799, (float)1.717773, (float)2.000244,
- (float)0.972656, (float)1.260986, (float)1.760620,
- (float)1.028198, (float)1.288452, (float)1.484619,
- Andersen, et al. Experimental [Page 92]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)0.773560, (float)1.258057, (float)1.756714,
- (float)1.080322, (float)1.328003, (float)1.742676,
- (float)0.823975, (float)1.450806, (float)1.917725,
- (float)0.859009, (float)1.016602, (float)1.191895,
- (float)0.843994, (float)1.131104, (float)1.645020,
- (float)1.189697, (float)1.702759, (float)1.894409,
- (float)1.346680, (float)1.763184, (float)2.066040,
- (float)0.980469, (float)1.253784, (float)1.441650,
- (float)1.338135, (float)1.641968, (float)1.932739,
- (float)1.223267, (float)1.424194, (float)1.626465,
- (float)0.765747, (float)1.004150, (float)1.579102,
- (float)1.042847, (float)1.269165, (float)1.647461,
- (float)0.968750, (float)1.257568, (float)1.555786,
- (float)0.826294, (float)0.993408, (float)1.275146,
- (float)0.742310, (float)0.950439, (float)1.430542,
- (float)1.054321, (float)1.439819, (float)1.828003,
- (float)1.072998, (float)1.261719, (float)1.441895,
- (float)0.859375, (float)1.036377, (float)1.314819,
- (float)0.895752, (float)1.267212, (float)1.605591,
- (float)0.805420, (float)0.962891, (float)1.142334,
- (float)0.795654, (float)1.005493, (float)1.468506,
- (float)1.105347, (float)1.313843, (float)1.584839,
- (float)0.792236, (float)1.221802, (float)1.465698,
- (float)1.170532, (float)1.467651, (float)1.664063,
- (float)0.838257, (float)1.153198, (float)1.342163,
- (float)0.968018, (float)1.198242, (float)1.391235,
- (float)1.250122, (float)1.623535, (float)1.823608,
- (float)0.711670, (float)1.058350, (float)1.512085,
- (float)1.204834, (float)1.454468, (float)1.739136,
- (float)1.137451, (float)1.421753, (float)1.620117,
- (float)0.820435, (float)1.322754, (float)1.578247,
- (float)0.798706, (float)1.005005, (float)1.213867,
- (float)0.980713, (float)1.324951, (float)1.512939,
- (float)1.112305, (float)1.438843, (float)1.735596,
- (float)1.135498, (float)1.356689, (float)1.635742,
- (float)1.101318, (float)1.387451, (float)1.686523,
- (float)0.849854, (float)1.276978, (float)1.523438,
- (float)1.377930, (float)1.627563, (float)1.858154,
- (float)0.884888, (float)1.095459, (float)1.287476,
- (float)1.289795, (float)1.505859, (float)1.756592,
- (float)0.817505, (float)1.384155, (float)1.650513,
- (float)1.446655, (float)1.702148, (float)1.931885,
- (float)0.835815, (float)1.023071, (float)1.385376,
- (float)0.916626, (float)1.139038, (float)1.335327,
- (float)0.980103, (float)1.174072, (float)1.453735,
- (float)1.705688, (float)2.153809, (float)2.398315, (float)2.743408,
- (float)1.797119, (float)2.016846, (float)2.445679, (float)2.701904,
- (float)1.990356, (float)2.219116, (float)2.576416, (float)2.813477,
- Andersen, et al. Experimental [Page 93]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)1.849365, (float)2.190918, (float)2.611572, (float)2.835083,
- (float)1.657959, (float)1.854370, (float)2.159058, (float)2.726196,
- (float)1.437744, (float)1.897705, (float)2.253174, (float)2.655396,
- (float)2.028687, (float)2.247314, (float)2.542358, (float)2.875854,
- (float)1.736938, (float)1.922119, (float)2.185913, (float)2.743408,
- (float)1.521606, (float)1.870972, (float)2.526855, (float)2.786987,
- (float)1.841431, (float)2.050659, (float)2.463623, (float)2.857666,
- (float)1.590088, (float)2.067261, (float)2.427979, (float)2.794434,
- (float)1.746826, (float)2.057373, (float)2.320190, (float)2.800781,
- (float)1.734619, (float)1.940552, (float)2.306030, (float)2.826416,
- (float)1.786255, (float)2.204468, (float)2.457520, (float)2.795288,
- (float)1.861084, (float)2.170532, (float)2.414551, (float)2.763672,
- (float)2.001465, (float)2.307617, (float)2.552734, (float)2.811890,
- (float)1.784424, (float)2.124146, (float)2.381592, (float)2.645508,
- (float)1.888794, (float)2.135864, (float)2.418579, (float)2.861206,
- (float)2.301147, (float)2.531250, (float)2.724976, (float)2.913086,
- (float)1.837769, (float)2.051270, (float)2.261963, (float)2.553223,
- (float)2.012939, (float)2.221191, (float)2.440186, (float)2.678101,
- (float)1.429565, (float)1.858276, (float)2.582275, (float)2.845703,
- (float)1.622803, (float)1.897705, (float)2.367310, (float)2.621094,
- (float)1.581543, (float)1.960449, (float)2.515869, (float)2.736450,
- (float)1.419434, (float)1.933960, (float)2.394653, (float)2.746704,
- (float)1.721924, (float)2.059570, (float)2.421753, (float)2.769653,
- (float)1.911011, (float)2.220703, (float)2.461060, (float)2.740723,
- (float)1.581177, (float)1.860840, (float)2.516968, (float)2.874634,
- (float)1.870361, (float)2.098755, (float)2.432373, (float)2.656494,
- (float)2.059692, (float)2.279785, (float)2.495605, (float)2.729370,
- (float)1.815674, (float)2.181519, (float)2.451538, (float)2.680542,
- (float)1.407959, (float)1.768311, (float)2.343018, (float)2.668091,
- (float)2.168701, (float)2.394653, (float)2.604736, (float)2.829346,
- (float)1.636230, (float)1.865723, (float)2.329102, (float)2.824219,
- (float)1.878906, (float)2.139526, (float)2.376709, (float)2.679810,
- (float)1.765381, (float)1.971802, (float)2.195435, (float)2.586914,
- (float)2.164795, (float)2.410889, (float)2.673706, (float)2.903198,
- (float)2.071899, (float)2.331055, (float)2.645874, (float)2.907104,
- (float)2.026001, (float)2.311523, (float)2.594849, (float)2.863892,
- (float)1.948975, (float)2.180786, (float)2.514893, (float)2.797852,
- (float)1.881836, (float)2.130859, (float)2.478149, (float)2.804199,
- (float)2.238159, (float)2.452759, (float)2.652832, (float)2.868286,
- (float)1.897949, (float)2.101685, (float)2.524292, (float)2.880127,
- (float)1.856445, (float)2.074585, (float)2.541016, (float)2.791748,
- (float)1.695557, (float)2.199097, (float)2.506226, (float)2.742676,
- (float)1.612671, (float)1.877075, (float)2.435425, (float)2.732910,
- (float)1.568848, (float)1.786499, (float)2.194580, (float)2.768555,
- (float)1.953369, (float)2.164551, (float)2.486938, (float)2.874023,
- (float)1.388306, (float)1.725342, (float)2.384521, (float)2.771851,
- (float)2.115356, (float)2.337769, (float)2.592896, (float)2.864014,
- (float)1.905762, (float)2.111328, (float)2.363525, (float)2.789307,
- Andersen, et al. Experimental [Page 94]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)1.882568, (float)2.332031, (float)2.598267, (float)2.827637,
- (float)1.683594, (float)2.088745, (float)2.361938, (float)2.608643,
- (float)1.874023, (float)2.182129, (float)2.536133, (float)2.766968,
- (float)1.861938, (float)2.070435, (float)2.309692, (float)2.700562,
- (float)1.722168, (float)2.107422, (float)2.477295, (float)2.837646,
- (float)1.926880, (float)2.184692, (float)2.442627, (float)2.663818,
- (float)2.123901, (float)2.337280, (float)2.553101, (float)2.777466,
- (float)1.588135, (float)1.911499, (float)2.212769, (float)2.543945,
- (float)2.053955, (float)2.370850, (float)2.712158, (float)2.939941,
- (float)2.210449, (float)2.519653, (float)2.770386, (float)2.958618,
- (float)2.199463, (float)2.474731, (float)2.718262, (float)2.919922,
- (float)1.960083, (float)2.175415, (float)2.608032, (float)2.888794,
- (float)1.953735, (float)2.185181, (float)2.428223, (float)2.809570,
- (float)1.615234, (float)2.036499, (float)2.576538, (float)2.834595,
- (float)1.621094, (float)2.028198, (float)2.431030, (float)2.664673,
- (float)1.824951, (float)2.267456, (float)2.514526, (float)2.747925,
- (float)1.994263, (float)2.229126, (float)2.475220, (float)2.833984,
- (float)1.746338, (float)2.011353, (float)2.588257, (float)2.826904,
- (float)1.562866, (float)2.135986, (float)2.471680, (float)2.687256,
- (float)1.748901, (float)2.083496, (float)2.460938, (float)2.686279,
- (float)1.758057, (float)2.131470, (float)2.636597, (float)2.891602,
- (float)2.071289, (float)2.299072, (float)2.550781, (float)2.814331,
- (float)1.839600, (float)2.094360, (float)2.496460, (float)2.723999,
- (float)1.882202, (float)2.088257, (float)2.636841, (float)2.923096,
- (float)1.957886, (float)2.153198, (float)2.384399, (float)2.615234,
- (float)1.992920, (float)2.351196, (float)2.654419, (float)2.889771,
- (float)2.012817, (float)2.262451, (float)2.643799, (float)2.903076,
- (float)2.025635, (float)2.254761, (float)2.508423, (float)2.784058,
- (float)2.316040, (float)2.589355, (float)2.794189, (float)2.963623,
- (float)1.741211, (float)2.279541, (float)2.578491, (float)2.816284,
- (float)1.845337, (float)2.055786, (float)2.348511, (float)2.822021,
- (float)1.679932, (float)1.926514, (float)2.499756, (float)2.835693,
- (float)1.722534, (float)1.946899, (float)2.448486, (float)2.728760,
- (float)1.829834, (float)2.043213, (float)2.580444, (float)2.867676,
- (float)1.676636, (float)2.071655, (float)2.322510, (float)2.704834,
- (float)1.791504, (float)2.113525, (float)2.469727, (float)2.784058,
- (float)1.977051, (float)2.215088, (float)2.497437, (float)2.726929,
- (float)1.800171, (float)2.106689, (float)2.357788, (float)2.738892,
- (float)1.827759, (float)2.170166, (float)2.525879, (float)2.852417,
- (float)1.918335, (float)2.132813, (float)2.488403, (float)2.728149,
- (float)1.916748, (float)2.225098, (float)2.542603, (float)2.857666,
- (float)1.761230, (float)1.976074, (float)2.507446, (float)2.884521,
- (float)2.053711, (float)2.367432, (float)2.608032, (float)2.837646,
- (float)1.595337, (float)2.000977, (float)2.307129, (float)2.578247,
- (float)1.470581, (float)2.031250, (float)2.375854, (float)2.647583,
- (float)1.801392, (float)2.128052, (float)2.399780, (float)2.822876,
- (float)1.853638, (float)2.066650, (float)2.429199, (float)2.751465,
- (float)1.956299, (float)2.163696, (float)2.394775, (float)2.734253,
- Andersen, et al. Experimental [Page 95]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)1.963623, (float)2.275757, (float)2.585327, (float)2.865234,
- (float)1.887451, (float)2.105469, (float)2.331787, (float)2.587402,
- (float)2.120117, (float)2.443359, (float)2.733887, (float)2.941406,
- (float)1.506348, (float)1.766968, (float)2.400513, (float)2.851807,
- (float)1.664551, (float)1.981079, (float)2.375732, (float)2.774414,
- (float)1.720703, (float)1.978882, (float)2.391479, (float)2.640991,
- (float)1.483398, (float)1.814819, (float)2.434448, (float)2.722290,
- (float)1.769043, (float)2.136597, (float)2.563721, (float)2.774414,
- (float)1.810791, (float)2.049316, (float)2.373901, (float)2.613647,
- (float)1.788330, (float)2.005981, (float)2.359131, (float)2.723145,
- (float)1.785156, (float)1.993164, (float)2.399780, (float)2.832520,
- (float)1.695313, (float)2.022949, (float)2.522583, (float)2.745117,
- (float)1.584106, (float)1.965576, (float)2.299927, (float)2.715576,
- (float)1.894897, (float)2.249878, (float)2.655884, (float)2.897705,
- (float)1.720581, (float)1.995728, (float)2.299438, (float)2.557007,
- (float)1.619385, (float)2.173950, (float)2.574219, (float)2.787964,
- (float)1.883179, (float)2.220459, (float)2.474365, (float)2.825073,
- (float)1.447632, (float)2.045044, (float)2.555542, (float)2.744873,
- (float)1.502686, (float)2.156616, (float)2.653320, (float)2.846558,
- (float)1.711548, (float)1.944092, (float)2.282959, (float)2.685791,
- (float)1.499756, (float)1.867554, (float)2.341064, (float)2.578857,
- (float)1.916870, (float)2.135132, (float)2.568237, (float)2.826050,
- (float)1.498047, (float)1.711182, (float)2.223267, (float)2.755127,
- (float)1.808716, (float)1.997559, (float)2.256470, (float)2.758545,
- (float)2.088501, (float)2.402710, (float)2.667358, (float)2.890259,
- (float)1.545044, (float)1.819214, (float)2.324097, (float)2.692993,
- (float)1.796021, (float)2.012573, (float)2.505737, (float)2.784912,
- (float)1.786499, (float)2.041748, (float)2.290405, (float)2.650757,
- (float)1.938232, (float)2.264404, (float)2.529053, (float)2.796143
- };
- A.9. anaFilter.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- anaFilter.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_ANAFILTER_H
- #define __iLBC_ANAFILTER_H
- void anaFilter(
- Andersen, et al. Experimental [Page 96]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *In, /* (i) Signal to be filtered */
- float *a, /* (i) LP parameters */
- int len,/* (i) Length of signal */
- float *Out, /* (o) Filtered signal */
- float *mem /* (i/o) Filter state */
- );
- #endif
- A.10. anaFilter.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- anaFilter.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <string.h>
- #include "iLBC_define.h"
- /*----------------------------------------------------------------*
- * LP analysis filter.
- *---------------------------------------------------------------*/
- void anaFilter(
- float *In, /* (i) Signal to be filtered */
- float *a, /* (i) LP parameters */
- int len,/* (i) Length of signal */
- float *Out, /* (o) Filtered signal */
- float *mem /* (i/o) Filter state */
- ){
- int i, j;
- float *po, *pi, *pm, *pa;
- po = Out;
- /* Filter first part using memory from past */
- for (i=0; i<LPC_FILTERORDER; i++) {
- pi = &In[i];
- pm = &mem[LPC_FILTERORDER-1];
- pa = a;
- *po=0.0;
- Andersen, et al. Experimental [Page 97]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (j=0; j<=i; j++) {
- *po+=(*pa++)*(*pi--);
- }
- for (j=i+1; j<LPC_FILTERORDER+1; j++) {
- *po+=(*pa++)*(*pm--);
- }
- po++;
- }
- /* Filter last part where the state is entirely
- in the input vector */
- for (i=LPC_FILTERORDER; i<len; i++) {
- pi = &In[i];
- pa = a;
- *po=0.0;
- for (j=0; j<LPC_FILTERORDER+1; j++) {
- *po+=(*pa++)*(*pi--);
- }
- po++;
- }
- /* Update state vector */
- memcpy(mem, &In[len-LPC_FILTERORDER],
- LPC_FILTERORDER*sizeof(float));
- }
- A.11. createCB.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- createCB.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_CREATECB_H
- #define __iLBC_CREATECB_H
- void filteredCBvecs(
- float *cbvectors, /* (o) Codebook vector for the
- higher section */
- Andersen, et al. Experimental [Page 98]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *mem, /* (i) Buffer to create codebook
- vectors from */
- int lMem /* (i) Length of buffer */
- );
- void searchAugmentedCB(
- int low, /* (i) Start index for the search */
- int high, /* (i) End index for the search */
- int stage, /* (i) Current stage */
- int startIndex, /* (i) CB index for the first
- augmented vector */
- float *target, /* (i) Target vector for encoding */
- float *buffer, /* (i) Pointer to the end of the
- buffer for augmented codebook
- construction */
- float *max_measure, /* (i/o) Currently maximum measure */
- int *best_index,/* (o) Currently the best index */
- float *gain, /* (o) Currently the best gain */
- float *energy, /* (o) Energy of augmented
- codebook vectors */
- float *invenergy/* (o) Inv energy of aug codebook
- vectors */
- );
- void createAugmentedVec(
- int index, /* (i) Index for the aug vector
- to be created */
- float *buffer, /* (i) Pointer to the end of the
- buffer for augmented codebook
- construction */
- float *cbVec /* (o) The construced codebook vector */
- );
- #endif
- A.12. createCB.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- createCB.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- Andersen, et al. Experimental [Page 99]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #include "iLBC_define.h"
- #include "constants.h"
- #include <string.h>
- #include <math.h>
- /*----------------------------------------------------------------*
- * Construct an additional codebook vector by filtering the
- * initial codebook buffer. This vector is then used to expand
- * the codebook with an additional section.
- *---------------------------------------------------------------*/
- void filteredCBvecs(
- float *cbvectors, /* (o) Codebook vectors for the
- higher section */
- float *mem, /* (i) Buffer to create codebook
- vector from */
- int lMem /* (i) Length of buffer */
- ){
- int j, k;
- float *pp, *pp1;
- float tempbuff2[CB_MEML+CB_FILTERLEN];
- float *pos;
- memset(tempbuff2, 0, (CB_HALFFILTERLEN-1)*sizeof(float));
- memcpy(&tempbuff2[CB_HALFFILTERLEN-1], mem, lMem*sizeof(float));
- memset(&tempbuff2[lMem+CB_HALFFILTERLEN-1], 0,
- (CB_HALFFILTERLEN+1)*sizeof(float));
- /* Create codebook vector for higher section by filtering */
- /* do filtering */
- pos=cbvectors;
- memset(pos, 0, lMem*sizeof(float));
- for (k=0; k<lMem; k++) {
- pp=&tempbuff2[k];
- pp1=&cbfiltersTbl[CB_FILTERLEN-1];
- for (j=0;j<CB_FILTERLEN;j++) {
- (*pos)+=(*pp++)*(*pp1--);
- }
- pos++;
- }
- }
- /*----------------------------------------------------------------*
- * Search the augmented part of the codebook to find the best
- * measure.
- *----------------------------------------------------------------*/
- Andersen, et al. Experimental [Page 100]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void searchAugmentedCB(
- int low, /* (i) Start index for the search */
- int high, /* (i) End index for the search */
- int stage, /* (i) Current stage */
- int startIndex, /* (i) Codebook index for the first
- aug vector */
- float *target, /* (i) Target vector for encoding */
- float *buffer, /* (i) Pointer to the end of the buffer for
- augmented codebook construction */
- float *max_measure, /* (i/o) Currently maximum measure */
- int *best_index,/* (o) Currently the best index */
- float *gain, /* (o) Currently the best gain */
- float *energy, /* (o) Energy of augmented codebook
- vectors */
- float *invenergy/* (o) Inv energy of augmented codebook
- vectors */
- ) {
- int icount, ilow, j, tmpIndex;
- float *pp, *ppo, *ppi, *ppe, crossDot, alfa;
- float weighted, measure, nrjRecursive;
- float ftmp;
- /* Compute the energy for the first (low-5)
- noninterpolated samples */
- nrjRecursive = (float) 0.0;
- pp = buffer - low + 1;
- for (j=0; j<(low-5); j++) {
- nrjRecursive += ( (*pp)*(*pp) );
- pp++;
- }
- ppe = buffer - low;
- for (icount=low; icount<=high; icount++) {
- /* Index of the codebook vector used for retrieving
- energy values */
- tmpIndex = startIndex+icount-20;
- ilow = icount-4;
- /* Update the energy recursively to save complexity */
- nrjRecursive = nrjRecursive + (*ppe)*(*ppe);
- ppe--;
- energy[tmpIndex] = nrjRecursive;
- /* Compute cross dot product for the first (low-5)
- samples */
- Andersen, et al. Experimental [Page 101]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- crossDot = (float) 0.0;
- pp = buffer-icount;
- for (j=0; j<ilow; j++) {
- crossDot += target[j]*(*pp++);
- }
- /* interpolation */
- alfa = (float) 0.2;
- ppo = buffer-4;
- ppi = buffer-icount-4;
- for (j=ilow; j<icount; j++) {
- weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi);
- ppo++;
- ppi++;
- energy[tmpIndex] += weighted*weighted;
- crossDot += target[j]*weighted;
- alfa += (float)0.2;
- }
- /* Compute energy and cross dot product for the
- remaining samples */
- pp = buffer - icount;
- for (j=icount; j<SUBL; j++) {
- energy[tmpIndex] += (*pp)*(*pp);
- crossDot += target[j]*(*pp++);
- }
- if (energy[tmpIndex]>0.0) {
- invenergy[tmpIndex]=(float)1.0/(energy[tmpIndex]+EPS);
- } else {
- invenergy[tmpIndex] = (float) 0.0;
- }
- if (stage==0) {
- measure = (float)-10000000.0;
- if (crossDot > 0.0) {
- measure = crossDot*crossDot*invenergy[tmpIndex];
- }
- }
- else {
- measure = crossDot*crossDot*invenergy[tmpIndex];
- }
- /* check if measure is better */
- ftmp = crossDot*invenergy[tmpIndex];
- if ((measure>*max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
- Andersen, et al. Experimental [Page 102]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- *best_index = tmpIndex;
- *max_measure = measure;
- *gain = ftmp;
- }
- }
- }
- /*----------------------------------------------------------------*
- * Recreate a specific codebook vector from the augmented part.
- *
- *----------------------------------------------------------------*/
- void createAugmentedVec(
- int index, /* (i) Index for the augmented vector
- to be created */
- float *buffer, /* (i) Pointer to the end of the buffer for
- augmented codebook construction */
- float *cbVec/* (o) The construced codebook vector */
- ) {
- int ilow, j;
- float *pp, *ppo, *ppi, alfa, alfa1, weighted;
- ilow = index-5;
- /* copy the first noninterpolated part */
- pp = buffer-index;
- memcpy(cbVec,pp,sizeof(float)*index);
- /* interpolation */
- alfa1 = (float)0.2;
- alfa = 0.0;
- ppo = buffer-5;
- ppi = buffer-index-5;
- for (j=ilow; j<index; j++) {
- weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi);
- ppo++;
- ppi++;
- cbVec[j] = weighted;
- alfa += alfa1;
- }
- /* copy the second noninterpolated part */
- pp = buffer - index;
- memcpy(cbVec+index,pp,sizeof(float)*(SUBL-index));
- Andersen, et al. Experimental [Page 103]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- A.13. doCPLC.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- doCPLC.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_DOLPC_H
- #define __iLBC_DOLPC_H
- void doThePLC(
- float *PLCresidual, /* (o) concealed residual */
- float *PLClpc, /* (o) concealed LP parameters */
- int PLI, /* (i) packet loss indicator
- 0 - no PL, 1 = PL */
- float *decresidual, /* (i) decoded residual */
- float *lpc, /* (i) decoded LPC (only used for no PL) */
- int inlag, /* (i) pitch lag */
- iLBC_Dec_Inst_t *iLBCdec_inst
- /* (i/o) decoder instance */
- );
- #endif
- A.14. doCPLC.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- doCPLC.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include <stdio.h>
- Andersen, et al. Experimental [Page 104]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #include "iLBC_define.h"
- /*----------------------------------------------------------------*
- * Compute cross correlation and pitch gain for pitch prediction
- * of last subframe at given lag.
- *---------------------------------------------------------------*/
- void compCorr(
- float *cc, /* (o) cross correlation coefficient */
- float *gc, /* (o) gain */
- float *pm,
- float *buffer, /* (i) signal buffer */
- int lag, /* (i) pitch lag */
- int bLen, /* (i) length of buffer */
- int sRange /* (i) correlation search length */
- ){
- int i;
- float ftmp1, ftmp2, ftmp3;
- /* Guard against getting outside buffer */
- if ((bLen-sRange-lag)<0) {
- sRange=bLen-lag;
- }
- ftmp1 = 0.0;
- ftmp2 = 0.0;
- ftmp3 = 0.0;
- for (i=0; i<sRange; i++) {
- ftmp1 += buffer[bLen-sRange+i] *
- buffer[bLen-sRange+i-lag];
- ftmp2 += buffer[bLen-sRange+i-lag] *
- buffer[bLen-sRange+i-lag];
- ftmp3 += buffer[bLen-sRange+i] *
- buffer[bLen-sRange+i];
- }
- if (ftmp2 > 0.0) {
- *cc = ftmp1*ftmp1/ftmp2;
- *gc = (float)fabs(ftmp1/ftmp2);
- *pm=(float)fabs(ftmp1)/
- ((float)sqrt(ftmp2)*(float)sqrt(ftmp3));
- }
- else {
- *cc = 0.0;
- *gc = 0.0;
- *pm=0.0;
- }
- }
- Andersen, et al. Experimental [Page 105]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /*----------------------------------------------------------------*
- * Packet loss concealment routine. Conceals a residual signal
- * and LP parameters. If no packet loss, update state.
- *---------------------------------------------------------------*/
- void doThePLC(
- float *PLCresidual, /* (o) concealed residual */
- float *PLClpc, /* (o) concealed LP parameters */
- int PLI, /* (i) packet loss indicator
- 0 - no PL, 1 = PL */
- float *decresidual, /* (i) decoded residual */
- float *lpc, /* (i) decoded LPC (only used for no PL) */
- int inlag, /* (i) pitch lag */
- iLBC_Dec_Inst_t *iLBCdec_inst
- /* (i/o) decoder instance */
- ){
- int lag=20, randlag;
- float gain, maxcc;
- float use_gain;
- float gain_comp, maxcc_comp, per, max_per;
- int i, pick, use_lag;
- float ftmp, randvec[BLOCKL_MAX], pitchfact, energy;
- /* Packet Loss */
- if (PLI == 1) {
- iLBCdec_inst->consPLICount += 1;
- /* if previous frame not lost,
- determine pitch pred. gain */
- if (iLBCdec_inst->prevPLI != 1) {
- /* Search around the previous lag to find the
- best pitch period */
- lag=inlag-3;
- compCorr(&maxcc, &gain, &max_per,
- iLBCdec_inst->prevResidual,
- lag, iLBCdec_inst->blockl, 60);
- for (i=inlag-2;i<=inlag+3;i++) {
- compCorr(&maxcc_comp, &gain_comp, &per,
- iLBCdec_inst->prevResidual,
- i, iLBCdec_inst->blockl, 60);
- if (maxcc_comp>maxcc) {
- maxcc=maxcc_comp;
- Andersen, et al. Experimental [Page 106]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- gain=gain_comp;
- lag=i;
- max_per=per;
- }
- }
- }
- /* previous frame lost, use recorded lag and periodicity */
- else {
- lag=iLBCdec_inst->prevLag;
- max_per=iLBCdec_inst->per;
- }
- /* downscaling */
- use_gain=1.0;
- if (iLBCdec_inst->consPLICount*iLBCdec_inst->blockl>320)
- use_gain=(float)0.9;
- else if (iLBCdec_inst->consPLICount*
- iLBCdec_inst->blockl>2*320)
- use_gain=(float)0.7;
- else if (iLBCdec_inst->consPLICount*
- iLBCdec_inst->blockl>3*320)
- use_gain=(float)0.5;
- else if (iLBCdec_inst->consPLICount*
- iLBCdec_inst->blockl>4*320)
- use_gain=(float)0.0;
- /* mix noise and pitch repeatition */
- ftmp=(float)sqrt(max_per);
- if (ftmp>(float)0.7)
- pitchfact=(float)1.0;
- else if (ftmp>(float)0.4)
- pitchfact=(ftmp-(float)0.4)/((float)0.7-(float)0.4);
- else
- pitchfact=0.0;
- /* avoid repetition of same pitch cycle */
- use_lag=lag;
- if (lag<80) {
- use_lag=2*lag;
- }
- /* compute concealed residual */
- Andersen, et al. Experimental [Page 107]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- energy = 0.0;
- for (i=0; i<iLBCdec_inst->blockl; i++) {
- /* noise component */
- iLBCdec_inst->seed=(iLBCdec_inst->seed*69069L+1) &
- (0x80000000L-1);
- randlag = 50 + ((signed long) iLBCdec_inst->seed)%70;
- pick = i - randlag;
- if (pick < 0) {
- randvec[i] =
- iLBCdec_inst->prevResidual[
- iLBCdec_inst->blockl+pick];
- } else {
- randvec[i] = randvec[pick];
- }
- /* pitch repeatition component */
- pick = i - use_lag;
- if (pick < 0) {
- PLCresidual[i] =
- iLBCdec_inst->prevResidual[
- iLBCdec_inst->blockl+pick];
- } else {
- PLCresidual[i] = PLCresidual[pick];
- }
- /* mix random and periodicity component */
- if (i<80)
- PLCresidual[i] = use_gain*(pitchfact *
- PLCresidual[i] +
- ((float)1.0 - pitchfact) * randvec[i]);
- else if (i<160)
- PLCresidual[i] = (float)0.95*use_gain*(pitchfact *
- PLCresidual[i] +
- ((float)1.0 - pitchfact) * randvec[i]);
- else
- PLCresidual[i] = (float)0.9*use_gain*(pitchfact *
- PLCresidual[i] +
- ((float)1.0 - pitchfact) * randvec[i]);
- energy += PLCresidual[i] * PLCresidual[i];
- }
- /* less than 30 dB, use only noise */
- Andersen, et al. Experimental [Page 108]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if (sqrt(energy/(float)iLBCdec_inst->blockl) < 30.0) {
- gain=0.0;
- for (i=0; i<iLBCdec_inst->blockl; i++) {
- PLCresidual[i] = randvec[i];
- }
- }
- /* use old LPC */
- memcpy(PLClpc,iLBCdec_inst->prevLpc,
- (LPC_FILTERORDER+1)*sizeof(float));
- }
- /* no packet loss, copy input */
- else {
- memcpy(PLCresidual, decresidual,
- iLBCdec_inst->blockl*sizeof(float));
- memcpy(PLClpc, lpc, (LPC_FILTERORDER+1)*sizeof(float));
- iLBCdec_inst->consPLICount = 0;
- }
- /* update state */
- if (PLI) {
- iLBCdec_inst->prevLag = lag;
- iLBCdec_inst->per=max_per;
- }
- iLBCdec_inst->prevPLI = PLI;
- memcpy(iLBCdec_inst->prevLpc, PLClpc,
- (LPC_FILTERORDER+1)*sizeof(float));
- memcpy(iLBCdec_inst->prevResidual, PLCresidual,
- iLBCdec_inst->blockl*sizeof(float));
- }
- A.15. enhancer.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- enhancer.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- Andersen, et al. Experimental [Page 109]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- ******************************************************************/
- #ifndef __ENHANCER_H
- #define __ENHANCER_H
- #include "iLBC_define.h"
- float xCorrCoef(
- float *target, /* (i) first array */
- float *regressor, /* (i) second array */
- int subl /* (i) dimension arrays */
- );
- int enhancerInterface(
- float *out, /* (o) the enhanced recidual signal */
- float *in, /* (i) the recidual signal to enhance */
- iLBC_Dec_Inst_t *iLBCdec_inst
- /* (i/o) the decoder state structure */
- );
- #endif
- A.16. enhancer.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- enhancer.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "constants.h"
- #include "filter.h"
- /*----------------------------------------------------------------*
- * Find index in array such that the array element with said
- * index is the element of said array closest to "value"
- * according to the squared-error criterion
- *---------------------------------------------------------------*/
- void NearestNeighbor(
- Andersen, et al. Experimental [Page 110]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- int *index, /* (o) index of array element closest
- to value */
- float *array, /* (i) data array */
- float value,/* (i) value */
- int arlength/* (i) dimension of data array */
- ){
- int i;
- float bestcrit,crit;
- crit=array[0]-value;
- bestcrit=crit*crit;
- *index=0;
- for (i=1; i<arlength; i++) {
- crit=array[i]-value;
- crit=crit*crit;
- if (crit<bestcrit) {
- bestcrit=crit;
- *index=i;
- }
- }
- }
- /*----------------------------------------------------------------*
- * compute cross correlation between sequences
- *---------------------------------------------------------------*/
- void mycorr1(
- float* corr, /* (o) correlation of seq1 and seq2 */
- float* seq1, /* (i) first sequence */
- int dim1, /* (i) dimension first seq1 */
- const float *seq2, /* (i) second sequence */
- int dim2 /* (i) dimension seq2 */
- ){
- int i,j;
- for (i=0; i<=dim1-dim2; i++) {
- corr[i]=0.0;
- for (j=0; j<dim2; j++) {
- corr[i] += seq1[i+j] * seq2[j];
- }
- }
- }
- /*----------------------------------------------------------------*
- * upsample finite array assuming zeros outside bounds
- *---------------------------------------------------------------*/
- Andersen, et al. Experimental [Page 111]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void enh_upsample(
- float* useq1, /* (o) upsampled output sequence */
- float* seq1,/* (i) unupsampled sequence */
- int dim1, /* (i) dimension seq1 */
- int hfl /* (i) polyphase filter length=2*hfl+1 */
- ){
- float *pu,*ps;
- int i,j,k,q,filterlength,hfl2;
- const float *polyp[ENH_UPS0]; /* pointers to
- polyphase columns */
- const float *pp;
- /* define pointers for filter */
- filterlength=2*hfl+1;
- if ( filterlength > dim1 ) {
- hfl2=(int) (dim1/2);
- for (j=0; j<ENH_UPS0; j++) {
- polyp[j]=polyphaserTbl+j*filterlength+hfl-hfl2;
- }
- hfl=hfl2;
- filterlength=2*hfl+1;
- }
- else {
- for (j=0; j<ENH_UPS0; j++) {
- polyp[j]=polyphaserTbl+j*filterlength;
- }
- }
- /* filtering: filter overhangs left side of sequence */
- pu=useq1;
- for (i=hfl; i<filterlength; i++) {
- for (j=0; j<ENH_UPS0; j++) {
- *pu=0.0;
- pp = polyp[j];
- ps = seq1+i;
- for (k=0; k<=i; k++) {
- *pu += *ps-- * *pp++;
- }
- pu++;
- }
- }
- /* filtering: simple convolution=inner products */
- for (i=filterlength; i<dim1; i++) {
- Andersen, et al. Experimental [Page 112]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (j=0;j<ENH_UPS0; j++){
- *pu=0.0;
- pp = polyp[j];
- ps = seq1+i;
- for (k=0; k<filterlength; k++) {
- *pu += *ps-- * *pp++;
- }
- pu++;
- }
- }
- /* filtering: filter overhangs right side of sequence */
- for (q=1; q<=hfl; q++) {
- for (j=0; j<ENH_UPS0; j++) {
- *pu=0.0;
- pp = polyp[j]+q;
- ps = seq1+dim1-1;
- for (k=0; k<filterlength-q; k++) {
- *pu += *ps-- * *pp++;
- }
- pu++;
- }
- }
- }
- /*----------------------------------------------------------------*
- * find segment starting near idata+estSegPos that has highest
- * correlation with idata+centerStartPos through
- * idata+centerStartPos+ENH_BLOCKL-1 segment is found at a
- * resolution of ENH_UPSO times the original of the original
- * sampling rate
- *---------------------------------------------------------------*/
- void refiner(
- float *seg, /* (o) segment array */
- float *updStartPos, /* (o) updated start point */
- float* idata, /* (i) original data buffer */
- int idatal, /* (i) dimension of idata */
- int centerStartPos, /* (i) beginning center segment */
- float estSegPos,/* (i) estimated beginning other segment */
- float period /* (i) estimated pitch period */
- ){
- int estSegPosRounded,searchSegStartPos,searchSegEndPos,corrdim;
- int tloc,tloc2,i,st,en,fraction;
- float vect[ENH_VECTL],corrVec[ENH_CORRDIM],maxv;
- float corrVecUps[ENH_CORRDIM*ENH_UPS0];
- Andersen, et al. Experimental [Page 113]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* defining array bounds */
- estSegPosRounded=(int)(estSegPos - 0.5);
- searchSegStartPos=estSegPosRounded-ENH_SLOP;
- if (searchSegStartPos<0) {
- searchSegStartPos=0;
- }
- searchSegEndPos=estSegPosRounded+ENH_SLOP;
- if (searchSegEndPos+ENH_BLOCKL >= idatal) {
- searchSegEndPos=idatal-ENH_BLOCKL-1;
- }
- corrdim=searchSegEndPos-searchSegStartPos+1;
- /* compute upsampled correlation (corr33) and find
- location of max */
- mycorr1(corrVec,idata+searchSegStartPos,
- corrdim+ENH_BLOCKL-1,idata+centerStartPos,ENH_BLOCKL);
- enh_upsample(corrVecUps,corrVec,corrdim,ENH_FL0);
- tloc=0; maxv=corrVecUps[0];
- for (i=1; i<ENH_UPS0*corrdim; i++) {
- if (corrVecUps[i]>maxv) {
- tloc=i;
- maxv=corrVecUps[i];
- }
- }
- /* make vector can be upsampled without ever running outside
- bounds */
- *updStartPos= (float)searchSegStartPos +
- (float)tloc/(float)ENH_UPS0+(float)1.0;
- tloc2=(int)(tloc/ENH_UPS0);
- if (tloc>tloc2*ENH_UPS0) {
- tloc2++;
- }
- st=searchSegStartPos+tloc2-ENH_FL0;
- if (st<0) {
- memset(vect,0,-st*sizeof(float));
- memcpy(&vect[-st],idata, (ENH_VECTL+st)*sizeof(float));
- }
- else {
- Andersen, et al. Experimental [Page 114]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- en=st+ENH_VECTL;
- if (en>idatal) {
- memcpy(vect, &idata[st],
- (ENH_VECTL-(en-idatal))*sizeof(float));
- memset(&vect[ENH_VECTL-(en-idatal)], 0,
- (en-idatal)*sizeof(float));
- }
- else {
- memcpy(vect, &idata[st], ENH_VECTL*sizeof(float));
- }
- }
- fraction=tloc2*ENH_UPS0-tloc;
- /* compute the segment (this is actually a convolution) */
- mycorr1(seg,vect,ENH_VECTL,polyphaserTbl+(2*ENH_FL0+1)*fraction,
- 2*ENH_FL0+1);
- }
- /*----------------------------------------------------------------*
- * find the smoothed output data
- *---------------------------------------------------------------*/
- void smath(
- float *odata, /* (o) smoothed output */
- float *sseq,/* (i) said second sequence of waveforms */
- int hl, /* (i) 2*hl+1 is sseq dimension */
- float alpha0/* (i) max smoothing energy fraction */
- ){
- int i,k;
- float w00,w10,w11,A,B,C,*psseq,err,errs;
- float surround[BLOCKL_MAX]; /* shape contributed by other than
- current */
- float wt[2*ENH_HL+1]; /* waveform weighting to get
- surround shape */
- float denom;
- /* create shape of contribution from all waveforms except the
- current one */
- for (i=1; i<=2*hl+1; i++) {
- wt[i-1] = (float)0.5*(1 - (float)cos(2*PI*i/(2*hl+2)));
- }
- wt[hl]=0.0; /* for clarity, not used */
- for (i=0; i<ENH_BLOCKL; i++) {
- surround[i]=sseq[i]*wt[0];
- }
- Andersen, et al. Experimental [Page 115]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (k=1; k<hl; k++) {
- psseq=sseq+k*ENH_BLOCKL;
- for(i=0;i<ENH_BLOCKL; i++) {
- surround[i]+=psseq[i]*wt[k];
- }
- }
- for (k=hl+1; k<=2*hl; k++) {
- psseq=sseq+k*ENH_BLOCKL;
- for(i=0;i<ENH_BLOCKL; i++) {
- surround[i]+=psseq[i]*wt[k];
- }
- }
- /* compute some inner products */
- w00 = w10 = w11 = 0.0;
- psseq=sseq+hl*ENH_BLOCKL; /* current block */
- for (i=0; i<ENH_BLOCKL;i++) {
- w00+=psseq[i]*psseq[i];
- w11+=surround[i]*surround[i];
- w10+=surround[i]*psseq[i];
- }
- if (fabs(w11) < 1.0) {
- w11=1.0;
- }
- C = (float)sqrt( w00/w11);
- /* first try enhancement without power-constraint */
- errs=0.0;
- psseq=sseq+hl*ENH_BLOCKL;
- for (i=0; i<ENH_BLOCKL; i++) {
- odata[i]=C*surround[i];
- err=psseq[i]-odata[i];
- errs+=err*err;
- }
- /* if constraint violated by first try, add constraint */
- if (errs > alpha0 * w00) {
- if ( w00 < 1) {
- w00=1;
- }
- denom = (w11*w00-w10*w10)/(w00*w00);
- if (denom > 0.0001) { /* eliminates numerical problems
- for if smooth */
- Andersen, et al. Experimental [Page 116]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A = (float)sqrt( (alpha0- alpha0*alpha0/4)/denom);
- B = -alpha0/2 - A * w10/w00;
- B = B+1;
- }
- else { /* essentially no difference between cycles;
- smoothing not needed */
- A= 0.0;
- B= 1.0;
- }
- /* create smoothed sequence */
- psseq=sseq+hl*ENH_BLOCKL;
- for (i=0; i<ENH_BLOCKL; i++) {
- odata[i]=A*surround[i]+B*psseq[i];
- }
- }
- }
- /*----------------------------------------------------------------*
- * get the pitch-synchronous sample sequence
- *---------------------------------------------------------------*/
- void getsseq(
- float *sseq, /* (o) the pitch-synchronous sequence */
- float *idata, /* (i) original data */
- int idatal, /* (i) dimension of data */
- int centerStartPos, /* (i) where current block starts */
- float *period, /* (i) rough-pitch-period array */
- float *plocs, /* (i) where periods of period array
- are taken */
- int periodl, /* (i) dimension period array */
- int hl /* (i) 2*hl+1 is the number of sequences */
- ){
- int i,centerEndPos,q;
- float blockStartPos[2*ENH_HL+1];
- int lagBlock[2*ENH_HL+1];
- float plocs2[ENH_PLOCSL];
- float *psseq;
- centerEndPos=centerStartPos+ENH_BLOCKL-1;
- /* present */
- NearestNeighbor(lagBlock+hl,plocs,
- (float)0.5*(centerStartPos+centerEndPos),periodl);
- blockStartPos[hl]=(float)centerStartPos;
- Andersen, et al. Experimental [Page 117]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- psseq=sseq+ENH_BLOCKL*hl;
- memcpy(psseq, idata+centerStartPos, ENH_BLOCKL*sizeof(float));
- /* past */
- for (q=hl-1; q>=0; q--) {
- blockStartPos[q]=blockStartPos[q+1]-period[lagBlock[q+1]];
- NearestNeighbor(lagBlock+q,plocs,
- blockStartPos[q]+
- ENH_BLOCKL_HALF-period[lagBlock[q+1]], periodl);
- if (blockStartPos[q]-ENH_OVERHANG>=0) {
- refiner(sseq+q*ENH_BLOCKL, blockStartPos+q, idata,
- idatal, centerStartPos, blockStartPos[q],
- period[lagBlock[q+1]]);
- } else {
- psseq=sseq+q*ENH_BLOCKL;
- memset(psseq, 0, ENH_BLOCKL*sizeof(float));
- }
- }
- /* future */
- for (i=0; i<periodl; i++) {
- plocs2[i]=plocs[i]-period[i];
- }
- for (q=hl+1; q<=2*hl; q++) {
- NearestNeighbor(lagBlock+q,plocs2,
- blockStartPos[q-1]+ENH_BLOCKL_HALF,periodl);
- blockStartPos[q]=blockStartPos[q-1]+period[lagBlock[q]];
- if (blockStartPos[q]+ENH_BLOCKL+ENH_OVERHANG<idatal) {
- refiner(sseq+ENH_BLOCKL*q, blockStartPos+q, idata,
- idatal, centerStartPos, blockStartPos[q],
- period[lagBlock[q]]);
- }
- else {
- psseq=sseq+q*ENH_BLOCKL;
- memset(psseq, 0, ENH_BLOCKL*sizeof(float));
- }
- }
- }
- /*----------------------------------------------------------------*
- * perform enhancement on idata+centerStartPos through
- * idata+centerStartPos+ENH_BLOCKL-1
- *---------------------------------------------------------------*/
- Andersen, et al. Experimental [Page 118]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void enhancer(
- float *odata, /* (o) smoothed block, dimension blockl */
- float *idata, /* (i) data buffer used for enhancing */
- int idatal, /* (i) dimension idata */
- int centerStartPos, /* (i) first sample current block
- within idata */
- float alpha0, /* (i) max correction-energy-fraction
- (in [0,1]) */
- float *period, /* (i) pitch period array */
- float *plocs, /* (i) locations where period array
- values valid */
- int periodl /* (i) dimension of period and plocs */
- ){
- float sseq[(2*ENH_HL+1)*ENH_BLOCKL];
- /* get said second sequence of segments */
- getsseq(sseq,idata,idatal,centerStartPos,period,
- plocs,periodl,ENH_HL);
- /* compute the smoothed output from said second sequence */
- smath(odata,sseq,ENH_HL,alpha0);
- }
- /*----------------------------------------------------------------*
- * cross correlation
- *---------------------------------------------------------------*/
- float xCorrCoef(
- float *target, /* (i) first array */
- float *regressor, /* (i) second array */
- int subl /* (i) dimension arrays */
- ){
- int i;
- float ftmp1, ftmp2;
- ftmp1 = 0.0;
- ftmp2 = 0.0;
- for (i=0; i<subl; i++) {
- ftmp1 += target[i]*regressor[i];
- ftmp2 += regressor[i]*regressor[i];
- }
- if (ftmp1 > 0.0) {
- return (float)(ftmp1*ftmp1/ftmp2);
- }
- Andersen, et al. Experimental [Page 119]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- else {
- return (float)0.0;
- }
- }
- /*----------------------------------------------------------------*
- * interface for enhancer
- *---------------------------------------------------------------*/
- int enhancerInterface(
- float *out, /* (o) enhanced signal */
- float *in, /* (i) unenhanced signal */
- iLBC_Dec_Inst_t *iLBCdec_inst /* (i) buffers etc */
- ){
- float *enh_buf, *enh_period;
- int iblock, isample;
- int lag=0, ilag, i, ioffset;
- float cc, maxcc;
- float ftmp1, ftmp2;
- float *inPtr, *enh_bufPtr1, *enh_bufPtr2;
- float plc_pred[ENH_BLOCKL];
- float lpState[6], downsampled[(ENH_NBLOCKS*ENH_BLOCKL+120)/2];
- int inLen=ENH_NBLOCKS*ENH_BLOCKL+120;
- int start, plc_blockl, inlag;
- enh_buf=iLBCdec_inst->enh_buf;
- enh_period=iLBCdec_inst->enh_period;
- memmove(enh_buf, &enh_buf[iLBCdec_inst->blockl],
- (ENH_BUFL-iLBCdec_inst->blockl)*sizeof(float));
- memcpy(&enh_buf[ENH_BUFL-iLBCdec_inst->blockl], in,
- iLBCdec_inst->blockl*sizeof(float));
- if (iLBCdec_inst->mode==30)
- plc_blockl=ENH_BLOCKL;
- else
- plc_blockl=40;
- /* when 20 ms frame, move processing one block */
- ioffset=0;
- if (iLBCdec_inst->mode==20) ioffset=1;
- i=3-ioffset;
- memmove(enh_period, &enh_period[i],
- (ENH_NBLOCKS_TOT-i)*sizeof(float));
- Andersen, et al. Experimental [Page 120]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* Set state information to the 6 samples right before
- the samples to be downsampled. */
- memcpy(lpState,
- enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-126,
- 6*sizeof(float));
- /* Down sample a factor 2 to save computations */
- DownSample(enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-120,
- lpFilt_coefsTbl, inLen-ioffset*ENH_BLOCKL,
- lpState, downsampled);
- /* Estimate the pitch in the down sampled domain. */
- for (iblock = 0; iblock<ENH_NBLOCKS-ioffset; iblock++) {
- lag = 10;
- maxcc = xCorrCoef(downsampled+60+iblock*
- ENH_BLOCKL_HALF, downsampled+60+iblock*
- ENH_BLOCKL_HALF-lag, ENH_BLOCKL_HALF);
- for (ilag=11; ilag<60; ilag++) {
- cc = xCorrCoef(downsampled+60+iblock*
- ENH_BLOCKL_HALF, downsampled+60+iblock*
- ENH_BLOCKL_HALF-ilag, ENH_BLOCKL_HALF);
- if (cc > maxcc) {
- maxcc = cc;
- lag = ilag;
- }
- }
- /* Store the estimated lag in the non-downsampled domain */
- enh_period[iblock+ENH_NBLOCKS_EXTRA+ioffset] = (float)lag*2;
- }
- /* PLC was performed on the previous packet */
- if (iLBCdec_inst->prev_enh_pl==1) {
- inlag=(int)enh_period[ENH_NBLOCKS_EXTRA+ioffset];
- lag = inlag-1;
- maxcc = xCorrCoef(in, in+lag, plc_blockl);
- for (ilag=inlag; ilag<=inlag+1; ilag++) {
- cc = xCorrCoef(in, in+ilag, plc_blockl);
- Andersen, et al. Experimental [Page 121]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if (cc > maxcc) {
- maxcc = cc;
- lag = ilag;
- }
- }
- enh_period[ENH_NBLOCKS_EXTRA+ioffset-1]=(float)lag;
- /* compute new concealed residual for the old lookahead,
- mix the forward PLC with a backward PLC from
- the new frame */
- inPtr=&in[lag-1];
- enh_bufPtr1=&plc_pred[plc_blockl-1];
- if (lag>plc_blockl) {
- start=plc_blockl;
- } else {
- start=lag;
- }
- for (isample = start; isample>0; isample--) {
- *enh_bufPtr1-- = *inPtr--;
- }
- enh_bufPtr2=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
- for (isample = (plc_blockl-1-lag); isample>=0; isample--) {
- *enh_bufPtr1-- = *enh_bufPtr2--;
- }
- /* limit energy change */
- ftmp2=0.0;
- ftmp1=0.0;
- for (i=0;i<plc_blockl;i++) {
- ftmp2+=enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]*
- enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i];
- ftmp1+=plc_pred[i]*plc_pred[i];
- }
- ftmp1=(float)sqrt(ftmp1/(float)plc_blockl);
- ftmp2=(float)sqrt(ftmp2/(float)plc_blockl);
- if (ftmp1>(float)2.0*ftmp2 && ftmp1>0.0) {
- for (i=0;i<plc_blockl-10;i++) {
- plc_pred[i]*=(float)2.0*ftmp2/ftmp1;
- }
- for (i=plc_blockl-10;i<plc_blockl;i++) {
- plc_pred[i]*=(float)(i-plc_blockl+10)*
- ((float)1.0-(float)2.0*ftmp2/ftmp1)/(float)(10)+
- Andersen, et al. Experimental [Page 122]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- (float)2.0*ftmp2/ftmp1;
- }
- }
- enh_bufPtr1=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
- for (i=0; i<plc_blockl; i++) {
- ftmp1 = (float) (i+1) / (float) (plc_blockl+1);
- *enh_bufPtr1 *= ftmp1;
- *enh_bufPtr1 += ((float)1.0-ftmp1)*
- plc_pred[plc_blockl-1-i];
- enh_bufPtr1--;
- }
- }
- if (iLBCdec_inst->mode==20) {
- /* Enhancer with 40 samples delay */
- for (iblock = 0; iblock<2; iblock++) {
- enhancer(out+iblock*ENH_BLOCKL, enh_buf,
- ENH_BUFL, (5+iblock)*ENH_BLOCKL+40,
- ENH_ALPHA0, enh_period, enh_plocsTbl,
- ENH_NBLOCKS_TOT);
- }
- } else if (iLBCdec_inst->mode==30) {
- /* Enhancer with 80 samples delay */
- for (iblock = 0; iblock<3; iblock++) {
- enhancer(out+iblock*ENH_BLOCKL, enh_buf,
- ENH_BUFL, (4+iblock)*ENH_BLOCKL,
- ENH_ALPHA0, enh_period, enh_plocsTbl,
- ENH_NBLOCKS_TOT);
- }
- }
- return (lag*2);
- }
- A.17. filter.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- filter.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- Andersen, et al. Experimental [Page 123]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #ifndef __iLBC_FILTER_H
- #define __iLBC_FILTER_H
- void AllPoleFilter(
- float *InOut, /* (i/o) on entrance InOut[-orderCoef] to
- InOut[-1] contain the state of the
- filter (delayed samples). InOut[0] to
- InOut[lengthInOut-1] contain the filter
- input, on en exit InOut[-orderCoef] to
- InOut[-1] is unchanged and InOut[0] to
- InOut[lengthInOut-1] contain filtered
- samples */
- float *Coef,/* (i) filter coefficients, Coef[0] is assumed
- to be 1.0 */
- int lengthInOut,/* (i) number of input/output samples */
- int orderCoef /* (i) number of filter coefficients */
- );
- void AllZeroFilter(
- float *In, /* (i) In[0] to In[lengthInOut-1] contain
- filter input samples */
- float *Coef,/* (i) filter coefficients (Coef[0] is assumed
- to be 1.0) */
- int lengthInOut,/* (i) number of input/output samples */
- int orderCoef, /* (i) number of filter coefficients */
- float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1]
- contain the filter state, on exit Out[0]
- to Out[lengthInOut-1] contain filtered
- samples */
- );
- void ZeroPoleFilter(
- float *In, /* (i) In[0] to In[lengthInOut-1] contain filter
- input samples In[-orderCoef] to In[-1]
- contain state of all-zero section */
- float *ZeroCoef,/* (i) filter coefficients for all-zero
- section (ZeroCoef[0] is assumed to
- be 1.0) */
- float *PoleCoef,/* (i) filter coefficients for all-pole section
- (ZeroCoef[0] is assumed to be 1.0) */
- int lengthInOut,/* (i) number of input/output samples */
- int orderCoef, /* (i) number of filter coefficients */
- float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1]
- contain state of all-pole section. On
- exit Out[0] to Out[lengthInOut-1]
- contain filtered samples */
- );
- Andersen, et al. Experimental [Page 124]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void DownSample (
- float *In, /* (i) input samples */
- float *Coef, /* (i) filter coefficients */
- int lengthIn, /* (i) number of input samples */
- float *state, /* (i) filter state */
- float *Out /* (o) downsampled output */
- );
- #endif
- A.18. filter.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- filter.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "iLBC_define.h"
- /*----------------------------------------------------------------*
- * all-pole filter
- *---------------------------------------------------------------*/
- void AllPoleFilter(
- float *InOut, /* (i/o) on entrance InOut[-orderCoef] to
- InOut[-1] contain the state of the
- filter (delayed samples). InOut[0] to
- InOut[lengthInOut-1] contain the filter
- input, on en exit InOut[-orderCoef] to
- InOut[-1] is unchanged and InOut[0] to
- InOut[lengthInOut-1] contain filtered
- samples */
- float *Coef,/* (i) filter coefficients, Coef[0] is assumed
- to be 1.0 */
- int lengthInOut,/* (i) number of input/output samples */
- int orderCoef /* (i) number of filter coefficients */
- ){
- int n,k;
- for(n=0;n<lengthInOut;n++){
- for(k=1;k<=orderCoef;k++){
- *InOut -= Coef[k]*InOut[-k];
- Andersen, et al. Experimental [Page 125]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- InOut++;
- }
- }
- /*----------------------------------------------------------------*
- * all-zero filter
- *---------------------------------------------------------------*/
- void AllZeroFilter(
- float *In, /* (i) In[0] to In[lengthInOut-1] contain
- filter input samples */
- float *Coef,/* (i) filter coefficients (Coef[0] is assumed
- to be 1.0) */
- int lengthInOut,/* (i) number of input/output samples */
- int orderCoef, /* (i) number of filter coefficients */
- float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1]
- contain the filter state, on exit Out[0]
- to Out[lengthInOut-1] contain filtered
- samples */
- ){
- int n,k;
- for(n=0;n<lengthInOut;n++){
- *Out = Coef[0]*In[0];
- for(k=1;k<=orderCoef;k++){
- *Out += Coef[k]*In[-k];
- }
- Out++;
- In++;
- }
- }
- /*----------------------------------------------------------------*
- * pole-zero filter
- *---------------------------------------------------------------*/
- void ZeroPoleFilter(
- float *In, /* (i) In[0] to In[lengthInOut-1] contain
- filter input samples In[-orderCoef] to
- In[-1] contain state of all-zero
- section */
- float *ZeroCoef,/* (i) filter coefficients for all-zero
- section (ZeroCoef[0] is assumed to
- be 1.0) */
- float *PoleCoef,/* (i) filter coefficients for all-pole section
- (ZeroCoef[0] is assumed to be 1.0) */
- int lengthInOut,/* (i) number of input/output samples */
- Andersen, et al. Experimental [Page 126]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- int orderCoef, /* (i) number of filter coefficients */
- float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1]
- contain state of all-pole section. On
- exit Out[0] to Out[lengthInOut-1]
- contain filtered samples */
- ){
- AllZeroFilter(In,ZeroCoef,lengthInOut,orderCoef,Out);
- AllPoleFilter(Out,PoleCoef,lengthInOut,orderCoef);
- }
- /*----------------------------------------------------------------*
- * downsample (LP filter and decimation)
- *---------------------------------------------------------------*/
- void DownSample (
- float *In, /* (i) input samples */
- float *Coef, /* (i) filter coefficients */
- int lengthIn, /* (i) number of input samples */
- float *state, /* (i) filter state */
- float *Out /* (o) downsampled output */
- ){
- float o;
- float *Out_ptr = Out;
- float *Coef_ptr, *In_ptr;
- float *state_ptr;
- int i, j, stop;
- /* LP filter and decimate at the same time */
- for (i = DELAY_DS; i < lengthIn; i+=FACTOR_DS)
- {
- Coef_ptr = &Coef[0];
- In_ptr = &In[i];
- state_ptr = &state[FILTERORDER_DS-2];
- o = (float)0.0;
- stop = (i < FILTERORDER_DS) ? i + 1 : FILTERORDER_DS;
- for (j = 0; j < stop; j++)
- {
- o += *Coef_ptr++ * (*In_ptr--);
- }
- for (j = i + 1; j < FILTERORDER_DS; j++)
- {
- o += *Coef_ptr++ * (*state_ptr--);
- }
- Andersen, et al. Experimental [Page 127]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- *Out_ptr++ = o;
- }
- /* Get the last part (use zeros as input for the future) */
- for (i=(lengthIn+FACTOR_DS); i<(lengthIn+DELAY_DS);
- i+=FACTOR_DS) {
- o=(float)0.0;
- if (i<lengthIn) {
- Coef_ptr = &Coef[0];
- In_ptr = &In[i];
- for (j=0; j<FILTERORDER_DS; j++) {
- o += *Coef_ptr++ * (*Out_ptr--);
- }
- } else {
- Coef_ptr = &Coef[i-lengthIn];
- In_ptr = &In[lengthIn-1];
- for (j=0; j<FILTERORDER_DS-(i-lengthIn); j++) {
- o += *Coef_ptr++ * (*In_ptr--);
- }
- }
- *Out_ptr++ = o;
- }
- }
- A.19. FrameClassify.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- FrameClassify.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_FRAMECLASSIFY_H
- #define __iLBC_FRAMECLASSIFY_H
- int FrameClassify( /* index to the max-energy sub-frame */
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i/o) the encoder state structure */
- float *residual /* (i) lpc residual signal */
- );
- Andersen, et al. Experimental [Page 128]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #endif
- A.20. FrameClassify.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- FrameClassify.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "iLBC_define.h"
- /*---------------------------------------------------------------*
- * Classification of subframes to localize start state
- *--------------------------------------------------------------*/
- int FrameClassify( /* index to the max-energy sub-frame */
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i/o) the encoder state structure */
- float *residual /* (i) lpc residual signal */
- ) {
- float max_ssqEn, fssqEn[NSUB_MAX], bssqEn[NSUB_MAX], *pp;
- int n, l, max_ssqEn_n;
- const float ssqEn_win[NSUB_MAX-1]={(float)0.8,(float)0.9,
- (float)1.0,(float)0.9,(float)0.8};
- const float sampEn_win[5]={(float)1.0/(float)6.0,
- (float)2.0/(float)6.0, (float)3.0/(float)6.0,
- (float)4.0/(float)6.0, (float)5.0/(float)6.0};
- /* init the front and back energies to zero */
- memset(fssqEn, 0, NSUB_MAX*sizeof(float));
- memset(bssqEn, 0, NSUB_MAX*sizeof(float));
- /* Calculate front of first seqence */
- n=0;
- pp=residual;
- for (l=0; l<5; l++) {
- fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
- pp++;
- }
- for (l=5; l<SUBL; l++) {
- Andersen, et al. Experimental [Page 129]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- fssqEn[n] += (*pp) * (*pp);
- pp++;
- }
- /* Calculate front and back of all middle sequences */
- for (n=1; n<iLBCenc_inst->nsub-1; n++) {
- pp=residual+n*SUBL;
- for (l=0; l<5; l++) {
- fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
- bssqEn[n] += (*pp) * (*pp);
- pp++;
- }
- for (l=5; l<SUBL-5; l++) {
- fssqEn[n] += (*pp) * (*pp);
- bssqEn[n] += (*pp) * (*pp);
- pp++;
- }
- for (l=SUBL-5; l<SUBL; l++) {
- fssqEn[n] += (*pp) * (*pp);
- bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
- pp++;
- }
- }
- /* Calculate back of last seqence */
- n=iLBCenc_inst->nsub-1;
- pp=residual+n*SUBL;
- for (l=0; l<SUBL-5; l++) {
- bssqEn[n] += (*pp) * (*pp);
- pp++;
- }
- for (l=SUBL-5; l<SUBL; l++) {
- bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
- pp++;
- }
- /* find the index to the weighted 80 sample with
- most energy */
- if (iLBCenc_inst->mode==20) l=1;
- else l=0;
- max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[l];
- max_ssqEn_n=1;
- for (n=2; n<iLBCenc_inst->nsub; n++) {
- Andersen, et al. Experimental [Page 130]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- l++;
- if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[l] > max_ssqEn) {
- max_ssqEn=(fssqEn[n-1]+bssqEn[n]) *
- ssqEn_win[l];
- max_ssqEn_n=n;
- }
- }
- return max_ssqEn_n;
- }
- A.21. gainquant.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- gainquant.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_GAINQUANT_H
- #define __iLBC_GAINQUANT_H
- float gainquant(/* (o) quantized gain value */
- float in, /* (i) gain value */
- float maxIn,/* (i) maximum of gain value */
- int cblen, /* (i) number of quantization indices */
- int *index /* (o) quantization index */
- );
- float gaindequant( /* (o) quantized gain value */
- int index, /* (i) quantization index */
- float maxIn,/* (i) maximum of unquantized gain */
- int cblen /* (i) number of quantization indices */
- );
- #endif
- A.22. gainquant.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- Andersen, et al. Experimental [Page 131]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- gainquant.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <string.h>
- #include <math.h>
- #include "constants.h"
- #include "filter.h"
- /*----------------------------------------------------------------*
- * quantizer for the gain in the gain-shape coding of residual
- *---------------------------------------------------------------*/
- float gainquant(/* (o) quantized gain value */
- float in, /* (i) gain value */
- float maxIn,/* (i) maximum of gain value */
- int cblen, /* (i) number of quantization indices */
- int *index /* (o) quantization index */
- ){
- int i, tindex;
- float minmeasure,measure, *cb, scale;
- /* ensure a lower bound on the scaling factor */
- scale=maxIn;
- if (scale<0.1) {
- scale=(float)0.1;
- }
- /* select the quantization table */
- if (cblen == 8) {
- cb = gain_sq3Tbl;
- } else if (cblen == 16) {
- cb = gain_sq4Tbl;
- } else {
- cb = gain_sq5Tbl;
- }
- /* select the best index in the quantization table */
- minmeasure=10000000.0;
- tindex=0;
- for (i=0; i<cblen; i++) {
- Andersen, et al. Experimental [Page 132]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- measure=(in-scale*cb[i])*(in-scale*cb[i]);
- if (measure<minmeasure) {
- tindex=i;
- minmeasure=measure;
- }
- }
- *index=tindex;
- /* return the quantized value */
- return scale*cb[tindex];
- }
- /*----------------------------------------------------------------*
- * decoder for quantized gains in the gain-shape coding of
- * residual
- *---------------------------------------------------------------*/
- float gaindequant( /* (o) quantized gain value */
- int index, /* (i) quantization index */
- float maxIn,/* (i) maximum of unquantized gain */
- int cblen /* (i) number of quantization indices */
- ){
- float scale;
- /* obtain correct scale factor */
- scale=(float)fabs(maxIn);
- if (scale<0.1) {
- scale=(float)0.1;
- }
- /* select the quantization table and return the decoded value */
- if (cblen==8) {
- return scale*gain_sq3Tbl[index];
- } else if (cblen==16) {
- return scale*gain_sq4Tbl[index];
- }
- else if (cblen==32) {
- return scale*gain_sq5Tbl[index];
- }
- return 0.0;
- }
- Andersen, et al. Experimental [Page 133]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.23. getCBvec.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- getCBvec.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_GETCBVEC_H
- #define __iLBC_GETCBVEC_H
- void getCBvec(
- float *cbvec, /* (o) Constructed codebook vector */
- float *mem, /* (i) Codebook buffer */
- int index, /* (i) Codebook index */
- int lMem, /* (i) Length of codebook buffer */
- int cbveclen/* (i) Codebook vector length */
- );
- #endif
- A.24. getCBvec.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- getCBvec.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "iLBC_define.h"
- #include "constants.h"
- #include <string.h>
- /*----------------------------------------------------------------*
- * Construct codebook vector for given index.
- *---------------------------------------------------------------*/
- void getCBvec(
- Andersen, et al. Experimental [Page 134]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *cbvec, /* (o) Constructed codebook vector */
- float *mem, /* (i) Codebook buffer */
- int index, /* (i) Codebook index */
- int lMem, /* (i) Length of codebook buffer */
- int cbveclen/* (i) Codebook vector length */
- ){
- int j, k, n, memInd, sFilt;
- float tmpbuf[CB_MEML];
- int base_size;
- int ilow, ihigh;
- float alfa, alfa1;
- /* Determine size of codebook sections */
- base_size=lMem-cbveclen+1;
- if (cbveclen==SUBL) {
- base_size+=cbveclen/2;
- }
- /* No filter -> First codebook section */
- if (index<lMem-cbveclen+1) {
- /* first non-interpolated vectors */
- k=index+cbveclen;
- /* get vector */
- memcpy(cbvec, mem+lMem-k, cbveclen*sizeof(float));
- } else if (index < base_size) {
- k=2*(index-(lMem-cbveclen+1))+cbveclen;
- ihigh=k/2;
- ilow=ihigh-5;
- /* Copy first noninterpolated part */
- memcpy(cbvec, mem+lMem-k/2, ilow*sizeof(float));
- /* interpolation */
- alfa1=(float)0.2;
- alfa=0.0;
- for (j=ilow; j<ihigh; j++) {
- cbvec[j]=((float)1.0-alfa)*mem[lMem-k/2+j]+
- alfa*mem[lMem-k+j];
- Andersen, et al. Experimental [Page 135]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- alfa+=alfa1;
- }
- /* Copy second noninterpolated part */
- memcpy(cbvec+ihigh, mem+lMem-k+ihigh,
- (cbveclen-ihigh)*sizeof(float));
- }
- /* Higher codebook section based on filtering */
- else {
- /* first non-interpolated vectors */
- if (index-base_size<lMem-cbveclen+1) {
- float tempbuff2[CB_MEML+CB_FILTERLEN+1];
- float *pos;
- float *pp, *pp1;
- memset(tempbuff2, 0,
- CB_HALFFILTERLEN*sizeof(float));
- memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
- lMem*sizeof(float));
- memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
- (CB_HALFFILTERLEN+1)*sizeof(float));
- k=index-base_size+cbveclen;
- sFilt=lMem-k;
- memInd=sFilt+1-CB_HALFFILTERLEN;
- /* do filtering */
- pos=cbvec;
- memset(pos, 0, cbveclen*sizeof(float));
- for (n=0; n<cbveclen; n++) {
- pp=&tempbuff2[memInd+n+CB_HALFFILTERLEN];
- pp1=&cbfiltersTbl[CB_FILTERLEN-1];
- for (j=0; j<CB_FILTERLEN; j++) {
- (*pos)+=(*pp++)*(*pp1--);
- }
- pos++;
- }
- }
- /* interpolated vectors */
- else {
- Andersen, et al. Experimental [Page 136]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float tempbuff2[CB_MEML+CB_FILTERLEN+1];
- float *pos;
- float *pp, *pp1;
- int i;
- memset(tempbuff2, 0,
- CB_HALFFILTERLEN*sizeof(float));
- memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
- lMem*sizeof(float));
- memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
- (CB_HALFFILTERLEN+1)*sizeof(float));
- k=2*(index-base_size-
- (lMem-cbveclen+1))+cbveclen;
- sFilt=lMem-k;
- memInd=sFilt+1-CB_HALFFILTERLEN;
- /* do filtering */
- pos=&tmpbuf[sFilt];
- memset(pos, 0, k*sizeof(float));
- for (i=0; i<k; i++) {
- pp=&tempbuff2[memInd+i+CB_HALFFILTERLEN];
- pp1=&cbfiltersTbl[CB_FILTERLEN-1];
- for (j=0; j<CB_FILTERLEN; j++) {
- (*pos)+=(*pp++)*(*pp1--);
- }
- pos++;
- }
- ihigh=k/2;
- ilow=ihigh-5;
- /* Copy first noninterpolated part */
- memcpy(cbvec, tmpbuf+lMem-k/2,
- ilow*sizeof(float));
- /* interpolation */
- alfa1=(float)0.2;
- alfa=0.0;
- for (j=ilow; j<ihigh; j++) {
- cbvec[j]=((float)1.0-alfa)*
- tmpbuf[lMem-k/2+j]+alfa*tmpbuf[lMem-k+j];
- alfa+=alfa1;
- }
- Andersen, et al. Experimental [Page 137]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* Copy second noninterpolated part */
- memcpy(cbvec+ihigh, tmpbuf+lMem-k+ihigh,
- (cbveclen-ihigh)*sizeof(float));
- }
- }
- }
- A.25. helpfun.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- helpfun.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_HELPFUN_H
- #define __iLBC_HELPFUN_H
- void autocorr(
- float *r, /* (o) autocorrelation vector */
- const float *x, /* (i) data vector */
- int N, /* (i) length of data vector */
- int order /* largest lag for calculated
- autocorrelations */
- );
- void window(
- float *z, /* (o) the windowed data */
- const float *x, /* (i) the original data vector */
- const float *y, /* (i) the window */
- int N /* (i) length of all vectors */
- );
- void levdurb(
- float *a, /* (o) lpc coefficient vector starting
- with 1.0 */
- float *k, /* (o) reflection coefficients */
- float *r, /* (i) autocorrelation vector */
- int order /* (i) order of lpc filter */
- );
- void interpolate(
- Andersen, et al. Experimental [Page 138]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *out, /* (o) the interpolated vector */
- float *in1, /* (i) the first vector for the
- interpolation */
- float *in2, /* (i) the second vector for the
- interpolation */
- float coef, /* (i) interpolation weights */
- int length /* (i) length of all vectors */
- );
- void bwexpand(
- float *out, /* (o) the bandwidth expanded lpc
- coefficients */
- float *in, /* (i) the lpc coefficients before bandwidth
- expansion */
- float coef, /* (i) the bandwidth expansion factor */
- int length /* (i) the length of lpc coefficient vectors */
- );
- void vq(
- float *Xq, /* (o) the quantized vector */
- int *index, /* (o) the quantization index */
- const float *CB,/* (i) the vector quantization codebook */
- float *X, /* (i) the vector to quantize */
- int n_cb, /* (i) the number of vectors in the codebook */
- int dim /* (i) the dimension of all vectors */
- );
- void SplitVQ(
- float *qX, /* (o) the quantized vector */
- int *index, /* (o) a vector of indexes for all vector
- codebooks in the split */
- float *X, /* (i) the vector to quantize */
- const float *CB,/* (i) the quantizer codebook */
- int nsplit, /* the number of vector splits */
- const int *dim, /* the dimension of X and qX */
- const int *cbsize /* the number of vectors in the codebook */
- );
- void sort_sq(
- float *xq, /* (o) the quantized value */
- int *index, /* (o) the quantization index */
- float x, /* (i) the value to quantize */
- const float *cb,/* (i) the quantization codebook */
- int cb_size /* (i) the size of the quantization codebook */
- );
- int LSF_check( /* (o) 1 for stable lsf vectors and 0 for
- Andersen, et al. Experimental [Page 139]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- nonstable ones */
- float *lsf, /* (i) a table of lsf vectors */
- int dim, /* (i) the dimension of each lsf vector */
- int NoAn /* (i) the number of lsf vectors in the
- table */
- );
- #endif
- A.26. helpfun.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- helpfun.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include "iLBC_define.h"
- #include "constants.h"
- /*----------------------------------------------------------------*
- * calculation of auto correlation
- *---------------------------------------------------------------*/
- void autocorr(
- float *r, /* (o) autocorrelation vector */
- const float *x, /* (i) data vector */
- int N, /* (i) length of data vector */
- int order /* largest lag for calculated
- autocorrelations */
- ){
- int lag, n;
- float sum;
- for (lag = 0; lag <= order; lag++) {
- sum = 0;
- for (n = 0; n < N - lag; n++) {
- sum += x[n] * x[n+lag];
- }
- r[lag] = sum;
- }
- Andersen, et al. Experimental [Page 140]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- /*----------------------------------------------------------------*
- * window multiplication
- *---------------------------------------------------------------*/
- void window(
- float *z, /* (o) the windowed data */
- const float *x, /* (i) the original data vector */
- const float *y, /* (i) the window */
- int N /* (i) length of all vectors */
- ){
- int i;
- for (i = 0; i < N; i++) {
- z[i] = x[i] * y[i];
- }
- }
- /*----------------------------------------------------------------*
- * levinson-durbin solution for lpc coefficients
- *---------------------------------------------------------------*/
- void levdurb(
- float *a, /* (o) lpc coefficient vector starting
- with 1.0 */
- float *k, /* (o) reflection coefficients */
- float *r, /* (i) autocorrelation vector */
- int order /* (i) order of lpc filter */
- ){
- float sum, alpha;
- int m, m_h, i;
- a[0] = 1.0;
- if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
- for (i = 0; i < order; i++) {
- k[i] = 0;
- a[i+1] = 0;
- }
- } else {
- a[1] = k[0] = -r[1]/r[0];
- alpha = r[0] + r[1] * k[0];
- for (m = 1; m < order; m++){
- sum = r[m + 1];
- for (i = 0; i < m; i++){
- sum += a[i+1] * r[m - i];
- }
- Andersen, et al. Experimental [Page 141]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- k[m] = -sum / alpha;
- alpha += k[m] * sum;
- m_h = (m + 1) >> 1;
- for (i = 0; i < m_h; i++){
- sum = a[i+1] + k[m] * a[m - i];
- a[m - i] += k[m] * a[i+1];
- a[i+1] = sum;
- }
- a[m+1] = k[m];
- }
- }
- }
- /*----------------------------------------------------------------*
- * interpolation between vectors
- *---------------------------------------------------------------*/
- void interpolate(
- float *out, /* (o) the interpolated vector */
- float *in1, /* (i) the first vector for the
- interpolation */
- float *in2, /* (i) the second vector for the
- interpolation */
- float coef, /* (i) interpolation weights */
- int length /* (i) length of all vectors */
- ){
- int i;
- float invcoef;
- invcoef = (float)1.0 - coef;
- for (i = 0; i < length; i++) {
- out[i] = coef * in1[i] + invcoef * in2[i];
- }
- }
- /*----------------------------------------------------------------*
- * lpc bandwidth expansion
- *---------------------------------------------------------------*/
- void bwexpand(
- float *out, /* (o) the bandwidth expanded lpc
- coefficients */
- float *in, /* (i) the lpc coefficients before bandwidth
- expansion */
- float coef, /* (i) the bandwidth expansion factor */
- int length /* (i) the length of lpc coefficient vectors */
- ){
- int i;
- Andersen, et al. Experimental [Page 142]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float chirp;
- chirp = coef;
- out[0] = in[0];
- for (i = 1; i < length; i++) {
- out[i] = chirp * in[i];
- chirp *= coef;
- }
- }
- /*----------------------------------------------------------------*
- * vector quantization
- *---------------------------------------------------------------*/
- void vq(
- float *Xq, /* (o) the quantized vector */
- int *index, /* (o) the quantization index */
- const float *CB,/* (i) the vector quantization codebook */
- float *X, /* (i) the vector to quantize */
- int n_cb, /* (i) the number of vectors in the codebook */
- int dim /* (i) the dimension of all vectors */
- ){
- int i, j;
- int pos, minindex;
- float dist, tmp, mindist;
- pos = 0;
- mindist = FLOAT_MAX;
- minindex = 0;
- for (j = 0; j < n_cb; j++) {
- dist = X[0] - CB[pos];
- dist *= dist;
- for (i = 1; i < dim; i++) {
- tmp = X[i] - CB[pos + i];
- dist += tmp*tmp;
- }
- if (dist < mindist) {
- mindist = dist;
- minindex = j;
- }
- pos += dim;
- }
- for (i = 0; i < dim; i++) {
- Xq[i] = CB[minindex*dim + i];
- }
- *index = minindex;
- Andersen, et al. Experimental [Page 143]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- /*----------------------------------------------------------------*
- * split vector quantization
- *---------------------------------------------------------------*/
- void SplitVQ(
- float *qX, /* (o) the quantized vector */
- int *index, /* (o) a vector of indexes for all vector
- codebooks in the split */
- float *X, /* (i) the vector to quantize */
- const float *CB,/* (i) the quantizer codebook */
- int nsplit, /* the number of vector splits */
- const int *dim, /* the dimension of X and qX */
- const int *cbsize /* the number of vectors in the codebook */
- ){
- int cb_pos, X_pos, i;
- cb_pos = 0;
- X_pos= 0;
- for (i = 0; i < nsplit; i++) {
- vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos,
- cbsize[i], dim[i]);
- X_pos += dim[i];
- cb_pos += dim[i] * cbsize[i];
- }
- }
- /*----------------------------------------------------------------*
- * scalar quantization
- *---------------------------------------------------------------*/
- void sort_sq(
- float *xq, /* (o) the quantized value */
- int *index, /* (o) the quantization index */
- float x, /* (i) the value to quantize */
- const float *cb,/* (i) the quantization codebook */
- int cb_size /* (i) the size of the quantization codebook */
- ){
- int i;
- if (x <= cb[0]) {
- *index = 0;
- *xq = cb[0];
- } else {
- i = 0;
- while ((x > cb[i]) && i < cb_size - 1) {
- i++;
- Andersen, et al. Experimental [Page 144]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- if (x > ((cb[i] + cb[i - 1])/2)) {
- *index = i;
- *xq = cb[i];
- } else {
- *index = i - 1;
- *xq = cb[i - 1];
- }
- }
- }
- /*----------------------------------------------------------------*
- * check for stability of lsf coefficients
- *---------------------------------------------------------------*/
- int LSF_check( /* (o) 1 for stable lsf vectors and 0 for
- nonstable ones */
- float *lsf, /* (i) a table of lsf vectors */
- int dim, /* (i) the dimension of each lsf vector */
- int NoAn /* (i) the number of lsf vectors in the
- table */
- ){
- int k,n,m, Nit=2, change=0,pos;
- float tmp;
- static float eps=(float)0.039; /* 50 Hz */
- static float eps2=(float)0.0195;
- static float maxlsf=(float)3.14; /* 4000 Hz */
- static float minlsf=(float)0.01; /* 0 Hz */
- /* LSF separation check*/
- for (n=0; n<Nit; n++) { /* Run through a couple of times */
- for (m=0; m<NoAn; m++) { /* Number of analyses per frame */
- for (k=0; k<(dim-1); k++) {
- pos=m*dim+k;
- if ((lsf[pos+1]-lsf[pos])<eps) {
- if (lsf[pos+1]<lsf[pos]) {
- tmp=lsf[pos+1];
- lsf[pos+1]= lsf[pos]+eps2;
- lsf[pos]= lsf[pos+1]-eps2;
- } else {
- lsf[pos]-=eps2;
- lsf[pos+1]+=eps2;
- }
- change=1;
- Andersen, et al. Experimental [Page 145]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- if (lsf[pos]<minlsf) {
- lsf[pos]=minlsf;
- change=1;
- }
- if (lsf[pos]>maxlsf) {
- lsf[pos]=maxlsf;
- change=1;
- }
- }
- }
- }
- return change;
- }
- A.27. hpInput.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- hpInput.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_HPINPUT_H
- #define __iLBC_HPINPUT_H
- void hpInput(
- float *In, /* (i) vector to filter */
- int len, /* (i) length of vector to filter */
- float *Out, /* (o) the resulting filtered vector */
- float *mem /* (i/o) the filter state */
- );
- #endif
- A.28. hpInput.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- Andersen, et al. Experimental [Page 146]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- hpInput.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "constants.h"
- /*----------------------------------------------------------------*
- * Input high-pass filter
- *---------------------------------------------------------------*/
- void hpInput(
- float *In, /* (i) vector to filter */
- int len, /* (i) length of vector to filter */
- float *Out, /* (o) the resulting filtered vector */
- float *mem /* (i/o) the filter state */
- ){
- int i;
- float *pi, *po;
- /* all-zero section*/
- pi = &In[0];
- po = &Out[0];
- for (i=0; i<len; i++) {
- *po = hpi_zero_coefsTbl[0] * (*pi);
- *po += hpi_zero_coefsTbl[1] * mem[0];
- *po += hpi_zero_coefsTbl[2] * mem[1];
- mem[1] = mem[0];
- mem[0] = *pi;
- po++;
- pi++;
- }
- /* all-pole section*/
- po = &Out[0];
- for (i=0; i<len; i++) {
- *po -= hpi_pole_coefsTbl[1] * mem[2];
- *po -= hpi_pole_coefsTbl[2] * mem[3];
- mem[3] = mem[2];
- mem[2] = *po;
- po++;
- Andersen, et al. Experimental [Page 147]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- }
- A.29. hpOutput.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- hpOutput.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_HPOUTPUT_H
- #define __iLBC_HPOUTPUT_H
- void hpOutput(
- float *In, /* (i) vector to filter */
- int len,/* (i) length of vector to filter */
- float *Out, /* (o) the resulting filtered vector */
- float *mem /* (i/o) the filter state */
- );
- #endif
- A.30. hpOutput.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- hpOutput.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "constants.h"
- /*----------------------------------------------------------------*
- * Output high-pass filter
- *---------------------------------------------------------------*/
- void hpOutput(
- Andersen, et al. Experimental [Page 148]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *In, /* (i) vector to filter */
- int len,/* (i) length of vector to filter */
- float *Out, /* (o) the resulting filtered vector */
- float *mem /* (i/o) the filter state */
- ){
- int i;
- float *pi, *po;
- /* all-zero section*/
- pi = &In[0];
- po = &Out[0];
- for (i=0; i<len; i++) {
- *po = hpo_zero_coefsTbl[0] * (*pi);
- *po += hpo_zero_coefsTbl[1] * mem[0];
- *po += hpo_zero_coefsTbl[2] * mem[1];
- mem[1] = mem[0];
- mem[0] = *pi;
- po++;
- pi++;
- }
- /* all-pole section*/
- po = &Out[0];
- for (i=0; i<len; i++) {
- *po -= hpo_pole_coefsTbl[1] * mem[2];
- *po -= hpo_pole_coefsTbl[2] * mem[3];
- mem[3] = mem[2];
- mem[2] = *po;
- po++;
- }
- }
- A.31. iCBConstruct.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iCBConstruct.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- Andersen, et al. Experimental [Page 149]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- ******************************************************************/
- #ifndef __iLBC_ICBCONSTRUCT_H
- #define __iLBC_ICBCONSTRUCT_H
- void index_conv_enc(
- int *index /* (i/o) Codebook indexes */
- );
- void index_conv_dec(
- int *index /* (i/o) Codebook indexes */
- );
- void iCBConstruct(
- float *decvector, /* (o) Decoded vector */
- int *index, /* (i) Codebook indices */
- int *gain_index,/* (i) Gain quantization indices */
- float *mem, /* (i) Buffer for codevector construction */
- int lMem, /* (i) Length of buffer */
- int veclen, /* (i) Length of vector */
- int nStages /* (i) Number of codebook stages */
- );
- #endif
- A.32. iCBConstruct.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iCBConstruct.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include "iLBC_define.h"
- #include "gainquant.h"
- #include "getCBvec.h"
- /*----------------------------------------------------------------*
- * Convert the codebook indexes to make the search easier
- *---------------------------------------------------------------*/
- Andersen, et al. Experimental [Page 150]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void index_conv_enc(
- int *index /* (i/o) Codebook indexes */
- ){
- int k;
- for (k=1; k<CB_NSTAGES; k++) {
- if ((index[k]>=108)&&(index[k]<172)) {
- index[k]-=64;
- } else if (index[k]>=236) {
- index[k]-=128;
- } else {
- /* ERROR */
- }
- }
- }
- void index_conv_dec(
- int *index /* (i/o) Codebook indexes */
- ){
- int k;
- for (k=1; k<CB_NSTAGES; k++) {
- if ((index[k]>=44)&&(index[k]<108)) {
- index[k]+=64;
- } else if ((index[k]>=108)&&(index[k]<128)) {
- index[k]+=128;
- } else {
- /* ERROR */
- }
- }
- }
- /*----------------------------------------------------------------*
- * Construct decoded vector from codebook and gains.
- *---------------------------------------------------------------*/
- void iCBConstruct(
- float *decvector, /* (o) Decoded vector */
- int *index, /* (i) Codebook indices */
- int *gain_index,/* (i) Gain quantization indices */
- float *mem, /* (i) Buffer for codevector construction */
- int lMem, /* (i) Length of buffer */
- int veclen, /* (i) Length of vector */
- int nStages /* (i) Number of codebook stages */
- ){
- int j,k;
- Andersen, et al. Experimental [Page 151]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float gain[CB_NSTAGES];
- float cbvec[SUBL];
- /* gain de-quantization */
- gain[0] = gaindequant(gain_index[0], 1.0, 32);
- if (nStages > 1) {
- gain[1] = gaindequant(gain_index[1],
- (float)fabs(gain[0]), 16);
- }
- if (nStages > 2) {
- gain[2] = gaindequant(gain_index[2],
- (float)fabs(gain[1]), 8);
- }
- /* codebook vector construction and construction of
- total vector */
- getCBvec(cbvec, mem, index[0], lMem, veclen);
- for (j=0;j<veclen;j++){
- decvector[j] = gain[0]*cbvec[j];
- }
- if (nStages > 1) {
- for (k=1; k<nStages; k++) {
- getCBvec(cbvec, mem, index[k], lMem, veclen);
- for (j=0;j<veclen;j++) {
- decvector[j] += gain[k]*cbvec[j];
- }
- }
- }
- }
- A.33. iCBSearch.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iCBSearch.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_ICBSEARCH_H
- #define __iLBC_ICBSEARCH_H
- Andersen, et al. Experimental [Page 152]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void iCBSearch(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) the encoder state structure */
- int *index, /* (o) Codebook indices */
- int *gain_index,/* (o) Gain quantization indices */
- float *intarget,/* (i) Target vector for encoding */
- float *mem, /* (i) Buffer for codebook construction */
- int lMem, /* (i) Length of buffer */
- int lTarget, /* (i) Length of vector */
- int nStages, /* (i) Number of codebook stages */
- float *weightDenum, /* (i) weighting filter coefficients */
- float *weightState, /* (i) weighting filter state */
- int block /* (i) the sub-block number */
- );
- #endif
- A.34. iCBSearch.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- iCBSearch.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "gainquant.h"
- #include "createCB.h"
- #include "filter.h"
- #include "constants.h"
- /*----------------------------------------------------------------*
- * Search routine for codebook encoding and gain quantization.
- *---------------------------------------------------------------*/
- void iCBSearch(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) the encoder state structure */
- int *index, /* (o) Codebook indices */
- int *gain_index,/* (o) Gain quantization indices */
- Andersen, et al. Experimental [Page 153]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *intarget,/* (i) Target vector for encoding */
- float *mem, /* (i) Buffer for codebook construction */
- int lMem, /* (i) Length of buffer */
- int lTarget, /* (i) Length of vector */
- int nStages, /* (i) Number of codebook stages */
- float *weightDenum, /* (i) weighting filter coefficients */
- float *weightState, /* (i) weighting filter state */
- int block /* (i) the sub-block number */
- ){
- int i, j, icount, stage, best_index, range, counter;
- float max_measure, gain, measure, crossDot, ftmp;
- float gains[CB_NSTAGES];
- float target[SUBL];
- int base_index, sInd, eInd, base_size;
- int sIndAug=0, eIndAug=0;
- float buf[CB_MEML+SUBL+2*LPC_FILTERORDER];
- float invenergy[CB_EXPAND*128], energy[CB_EXPAND*128];
- float *pp, *ppi=0, *ppo=0, *ppe=0;
- float cbvectors[CB_MEML];
- float tene, cene, cvec[SUBL];
- float aug_vec[SUBL];
- memset(cvec,0,SUBL*sizeof(float));
- /* Determine size of codebook sections */
- base_size=lMem-lTarget+1;
- if (lTarget==SUBL) {
- base_size=lMem-lTarget+1+lTarget/2;
- }
- /* setup buffer for weighting */
- memcpy(buf,weightState,sizeof(float)*LPC_FILTERORDER);
- memcpy(buf+LPC_FILTERORDER,mem,lMem*sizeof(float));
- memcpy(buf+LPC_FILTERORDER+lMem,intarget,lTarget*sizeof(float));
- /* weighting */
- AllPoleFilter(buf+LPC_FILTERORDER, weightDenum,
- lMem+lTarget, LPC_FILTERORDER);
- /* Construct the codebook and target needed */
- memcpy(target, buf+LPC_FILTERORDER+lMem, lTarget*sizeof(float));
- tene=0.0;
- Andersen, et al. Experimental [Page 154]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- for (i=0; i<lTarget; i++) {
- tene+=target[i]*target[i];
- }
- /* Prepare search over one more codebook section. This section
- is created by filtering the original buffer with a filter. */
- filteredCBvecs(cbvectors, buf+LPC_FILTERORDER, lMem);
- /* The Main Loop over stages */
- for (stage=0; stage<nStages; stage++) {
- range = search_rangeTbl[block][stage];
- /* initialize search measure */
- max_measure = (float)-10000000.0;
- gain = (float)0.0;
- best_index = 0;
- /* Compute cross dot product between the target
- and the CB memory */
- crossDot=0.0;
- pp=buf+LPC_FILTERORDER+lMem-lTarget;
- for (j=0; j<lTarget; j++) {
- crossDot += target[j]*(*pp++);
- }
- if (stage==0) {
- /* Calculate energy in the first block of
- 'lTarget' samples. */
- ppe = energy;
- ppi = buf+LPC_FILTERORDER+lMem-lTarget-1;
- ppo = buf+LPC_FILTERORDER+lMem-1;
- *ppe=0.0;
- pp=buf+LPC_FILTERORDER+lMem-lTarget;
- for (j=0; j<lTarget; j++) {
- *ppe+=(*pp)*(*pp++);
- }
- if (*ppe>0.0) {
- invenergy[0] = (float) 1.0 / (*ppe + EPS);
- } else {
- invenergy[0] = (float) 0.0;
- Andersen, et al. Experimental [Page 155]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- ppe++;
- measure=(float)-10000000.0;
- if (crossDot > 0.0) {
- measure = crossDot*crossDot*invenergy[0];
- }
- }
- else {
- measure = crossDot*crossDot*invenergy[0];
- }
- /* check if measure is better */
- ftmp = crossDot*invenergy[0];
- if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
- best_index = 0;
- max_measure = measure;
- gain = ftmp;
- }
- /* loop over the main first codebook section,
- full search */
- for (icount=1; icount<range; icount++) {
- /* calculate measure */
- crossDot=0.0;
- pp = buf+LPC_FILTERORDER+lMem-lTarget-icount;
- for (j=0; j<lTarget; j++) {
- crossDot += target[j]*(*pp++);
- }
- if (stage==0) {
- *ppe++ = energy[icount-1] + (*ppi)*(*ppi) -
- (*ppo)*(*ppo);
- ppo--;
- ppi--;
- if (energy[icount]>0.0) {
- invenergy[icount] =
- (float)1.0/(energy[icount]+EPS);
- } else {
- invenergy[icount] = (float) 0.0;
- }
- Andersen, et al. Experimental [Page 156]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- measure=(float)-10000000.0;
- if (crossDot > 0.0) {
- measure = crossDot*crossDot*invenergy[icount];
- }
- }
- else {
- measure = crossDot*crossDot*invenergy[icount];
- }
- /* check if measure is better */
- ftmp = crossDot*invenergy[icount];
- if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
- best_index = icount;
- max_measure = measure;
- gain = ftmp;
- }
- }
- /* Loop over augmented part in the first codebook
- * section, full search.
- * The vectors are interpolated.
- */
- if (lTarget==SUBL) {
- /* Search for best possible cb vector and
- compute the CB-vectors' energy. */
- searchAugmentedCB(20, 39, stage, base_size-lTarget/2,
- target, buf+LPC_FILTERORDER+lMem,
- &max_measure, &best_index, &gain, energy,
- invenergy);
- }
- /* set search range for following codebook sections */
- base_index=best_index;
- /* unrestricted search */
- if (CB_RESRANGE == -1) {
- sInd=0;
- eInd=range-1;
- sIndAug=20;
- eIndAug=39;
- }
- Andersen, et al. Experimental [Page 157]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* restricted search around best index from first
- codebook section */
- else {
- /* Initialize search indices */
- sIndAug=0;
- eIndAug=0;
- sInd=base_index-CB_RESRANGE/2;
- eInd=sInd+CB_RESRANGE;
- if (lTarget==SUBL) {
- if (sInd<0) {
- sIndAug = 40 + sInd;
- eIndAug = 39;
- sInd=0;
- } else if ( base_index < (base_size-20) ) {
- if (eInd > range) {
- sInd -= (eInd-range);
- eInd = range;
- }
- } else { /* base_index >= (base_size-20) */
- if (sInd < (base_size-20)) {
- sIndAug = 20;
- sInd = 0;
- eInd = 0;
- eIndAug = 19 + CB_RESRANGE;
- if(eIndAug > 39) {
- eInd = eIndAug-39;
- eIndAug = 39;
- }
- } else {
- sIndAug = 20 + sInd - (base_size-20);
- eIndAug = 39;
- sInd = 0;
- eInd = CB_RESRANGE - (eIndAug-sIndAug+1);
- }
- }
- } else { /* lTarget = 22 or 23 */
- if (sInd < 0) {
- eInd -= sInd;
- Andersen, et al. Experimental [Page 158]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- sInd = 0;
- }
- if(eInd > range) {
- sInd -= (eInd - range);
- eInd = range;
- }
- }
- }
- /* search of higher codebook section */
- /* index search range */
- counter = sInd;
- sInd += base_size;
- eInd += base_size;
- if (stage==0) {
- ppe = energy+base_size;
- *ppe=0.0;
- pp=cbvectors+lMem-lTarget;
- for (j=0; j<lTarget; j++) {
- *ppe+=(*pp)*(*pp++);
- }
- ppi = cbvectors + lMem - 1 - lTarget;
- ppo = cbvectors + lMem - 1;
- for (j=0; j<(range-1); j++) {
- *(ppe+1) = *ppe + (*ppi)*(*ppi) - (*ppo)*(*ppo);
- ppo--;
- ppi--;
- ppe++;
- }
- }
- /* loop over search range */
- for (icount=sInd; icount<eInd; icount++) {
- /* calculate measure */
- crossDot=0.0;
- pp=cbvectors + lMem - (counter++) - lTarget;
- for (j=0;j<lTarget;j++) {
- Andersen, et al. Experimental [Page 159]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- crossDot += target[j]*(*pp++);
- }
- if (energy[icount]>0.0) {
- invenergy[icount] =(float)1.0/(energy[icount]+EPS);
- } else {
- invenergy[icount] =(float)0.0;
- }
- if (stage==0) {
- measure=(float)-10000000.0;
- if (crossDot > 0.0) {
- measure = crossDot*crossDot*
- invenergy[icount];
- }
- }
- else {
- measure = crossDot*crossDot*invenergy[icount];
- }
- /* check if measure is better */
- ftmp = crossDot*invenergy[icount];
- if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
- best_index = icount;
- max_measure = measure;
- gain = ftmp;
- }
- }
- /* Search the augmented CB inside the limited range. */
- if ((lTarget==SUBL)&&(sIndAug!=0)) {
- searchAugmentedCB(sIndAug, eIndAug, stage,
- 2*base_size-20, target, cbvectors+lMem,
- &max_measure, &best_index, &gain, energy,
- invenergy);
- }
- /* record best index */
- index[stage] = best_index;
- /* gain quantization */
- if (stage==0){
- Andersen, et al. Experimental [Page 160]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if (gain<0.0){
- gain = 0.0;
- }
- if (gain>CB_MAXGAIN) {
- gain = (float)CB_MAXGAIN;
- }
- gain = gainquant(gain, 1.0, 32, &gain_index[stage]);
- }
- else {
- if (stage==1) {
- gain = gainquant(gain, (float)fabs(gains[stage-1]),
- 16, &gain_index[stage]);
- } else {
- gain = gainquant(gain, (float)fabs(gains[stage-1]),
- 8, &gain_index[stage]);
- }
- }
- /* Extract the best (according to measure)
- codebook vector */
- if (lTarget==(STATE_LEN-iLBCenc_inst->state_short_len)) {
- if (index[stage]<base_size) {
- pp=buf+LPC_FILTERORDER+lMem-lTarget-index[stage];
- } else {
- pp=cbvectors+lMem-lTarget-
- index[stage]+base_size;
- }
- } else {
- if (index[stage]<base_size) {
- if (index[stage]<(base_size-20)) {
- pp=buf+LPC_FILTERORDER+lMem-
- lTarget-index[stage];
- } else {
- createAugmentedVec(index[stage]-base_size+40,
- buf+LPC_FILTERORDER+lMem,aug_vec);
- pp=aug_vec;
- }
- } else {
- int filterno, position;
- filterno=index[stage]/base_size;
- position=index[stage]-filterno*base_size;
- Andersen, et al. Experimental [Page 161]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if (position<(base_size-20)) {
- pp=cbvectors+filterno*lMem-lTarget-
- index[stage]+filterno*base_size;
- } else {
- createAugmentedVec(
- index[stage]-(filterno+1)*base_size+40,
- cbvectors+filterno*lMem,aug_vec);
- pp=aug_vec;
- }
- }
- }
- /* Subtract the best codebook vector, according
- to measure, from the target vector */
- for (j=0;j<lTarget;j++) {
- cvec[j] += gain*(*pp);
- target[j] -= gain*(*pp++);
- }
- /* record quantized gain */
- gains[stage]=gain;
- }/* end of Main Loop. for (stage=0;... */
- /* Gain adjustment for energy matching */
- cene=0.0;
- for (i=0; i<lTarget; i++) {
- cene+=cvec[i]*cvec[i];
- }
- j=gain_index[0];
- for (i=gain_index[0]; i<32; i++) {
- ftmp=cene*gain_sq5Tbl[i]*gain_sq5Tbl[i];
- if ((ftmp<(tene*gains[0]*gains[0])) &&
- (gain_sq5Tbl[j]<(2.0*gains[0]))) {
- j=i;
- }
- }
- gain_index[0]=j;
- }
- Andersen, et al. Experimental [Page 162]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.35. LPCdecode.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- LPC_decode.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_LPC_DECODE_H
- #define __iLBC_LPC_DECODE_H
- void LSFinterpolate2a_dec(
- float *a, /* (o) lpc coefficients for a sub-frame */
- float *lsf1, /* (i) first lsf coefficient vector */
- float *lsf2, /* (i) second lsf coefficient vector */
- float coef, /* (i) interpolation weight */
- int length /* (i) length of lsf vectors */
- );
- void SimplelsfDEQ(
- float *lsfdeq, /* (o) dequantized lsf coefficients */
- int *index, /* (i) quantization index */
- int lpc_n /* (i) number of LPCs */
- );
- void DecoderInterpolateLSF(
- float *syntdenum, /* (o) synthesis filter coefficients */
- float *weightdenum, /* (o) weighting denumerator
- coefficients */
- float *lsfdeq, /* (i) dequantized lsf coefficients */
- int length, /* (i) length of lsf coefficient vector */
- iLBC_Dec_Inst_t *iLBCdec_inst
- /* (i) the decoder state structure */
- );
- #endif
- Andersen, et al. Experimental [Page 163]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.36. LPCdecode.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- LPC_decode.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include "helpfun.h"
- #include "lsf.h"
- #include "iLBC_define.h"
- #include "constants.h"
- /*---------------------------------------------------------------*
- * interpolation of lsf coefficients for the decoder
- *--------------------------------------------------------------*/
- void LSFinterpolate2a_dec(
- float *a, /* (o) lpc coefficients for a sub-frame */
- float *lsf1, /* (i) first lsf coefficient vector */
- float *lsf2, /* (i) second lsf coefficient vector */
- float coef, /* (i) interpolation weight */
- int length /* (i) length of lsf vectors */
- ){
- float lsftmp[LPC_FILTERORDER];
- interpolate(lsftmp, lsf1, lsf2, coef, length);
- lsf2a(a, lsftmp);
- }
- /*---------------------------------------------------------------*
- * obtain dequantized lsf coefficients from quantization index
- *--------------------------------------------------------------*/
- void SimplelsfDEQ(
- float *lsfdeq, /* (o) dequantized lsf coefficients */
- int *index, /* (i) quantization index */
- int lpc_n /* (i) number of LPCs */
- ){
- int i, j, pos, cb_pos;
- Andersen, et al. Experimental [Page 164]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* decode first LSF */
- pos = 0;
- cb_pos = 0;
- for (i = 0; i < LSF_NSPLIT; i++) {
- for (j = 0; j < dim_lsfCbTbl[i]; j++) {
- lsfdeq[pos + j] = lsfCbTbl[cb_pos +
- (long)(index[i])*dim_lsfCbTbl[i] + j];
- }
- pos += dim_lsfCbTbl[i];
- cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
- }
- if (lpc_n>1) {
- /* decode last LSF */
- pos = 0;
- cb_pos = 0;
- for (i = 0; i < LSF_NSPLIT; i++) {
- for (j = 0; j < dim_lsfCbTbl[i]; j++) {
- lsfdeq[LPC_FILTERORDER + pos + j] =
- lsfCbTbl[cb_pos +
- (long)(index[LSF_NSPLIT + i])*
- dim_lsfCbTbl[i] + j];
- }
- pos += dim_lsfCbTbl[i];
- cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
- }
- }
- }
- /*----------------------------------------------------------------*
- * obtain synthesis and weighting filters form lsf coefficients
- *---------------------------------------------------------------*/
- void DecoderInterpolateLSF(
- float *syntdenum, /* (o) synthesis filter coefficients */
- float *weightdenum, /* (o) weighting denumerator
- coefficients */
- float *lsfdeq, /* (i) dequantized lsf coefficients */
- int length, /* (i) length of lsf coefficient vector */
- iLBC_Dec_Inst_t *iLBCdec_inst
- /* (i) the decoder state structure */
- ){
- int i, pos, lp_length;
- float lp[LPC_FILTERORDER + 1], *lsfdeq2;
- Andersen, et al. Experimental [Page 165]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- lsfdeq2 = lsfdeq + length;
- lp_length = length + 1;
- if (iLBCdec_inst->mode==30) {
- /* sub-frame 1: Interpolation between old and first */
- LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq,
- lsf_weightTbl_30ms[0], length);
- memcpy(syntdenum,lp,lp_length*sizeof(float));
- bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM,
- lp_length);
- /* sub-frames 2 to 6: interpolation between first
- and last LSF */
- pos = lp_length;
- for (i = 1; i < 6; i++) {
- LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2,
- lsf_weightTbl_30ms[i], length);
- memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
- bwexpand(weightdenum + pos, lp,
- LPC_CHIRP_WEIGHTDENUM, lp_length);
- pos += lp_length;
- }
- }
- else {
- pos = 0;
- for (i = 0; i < iLBCdec_inst->nsub; i++) {
- LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold,
- lsfdeq, lsf_weightTbl_20ms[i], length);
- memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
- bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM,
- lp_length);
- pos += lp_length;
- }
- }
- /* update memory */
- if (iLBCdec_inst->mode==30)
- memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2,
- length*sizeof(float));
- else
- memcpy(iLBCdec_inst->lsfdeqold, lsfdeq,
- length*sizeof(float));
- }
- Andersen, et al. Experimental [Page 166]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.37. LPCencode.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- LPCencode.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_LPCENCOD_H
- #define __iLBC_LPCENCOD_H
- void LPCencode(
- float *syntdenum, /* (i/o) synthesis filter coefficients
- before/after encoding */
- float *weightdenum, /* (i/o) weighting denumerator coefficients
- before/after encoding */
- int *lsf_index, /* (o) lsf quantization index */
- float *data, /* (i) lsf coefficients to quantize */
- iLBC_Enc_Inst_t *iLBCenc_inst
- /* (i/o) the encoder state structure */
- );
- #endif
- A.38. LPCencode.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- LPCencode.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <string.h>
- #include "iLBC_define.h"
- #include "helpfun.h"
- #include "lsf.h"
- #include "constants.h"
- Andersen, et al. Experimental [Page 167]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /*----------------------------------------------------------------*
- * lpc analysis (subrutine to LPCencode)
- *---------------------------------------------------------------*/
- void SimpleAnalysis(
- float *lsf, /* (o) lsf coefficients */
- float *data, /* (i) new data vector */
- iLBC_Enc_Inst_t *iLBCenc_inst
- /* (i/o) the encoder state structure */
- ){
- int k, is;
- float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1];
- float lp2[LPC_FILTERORDER + 1];
- float r[LPC_FILTERORDER + 1];
- is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
- memcpy(iLBCenc_inst->lpc_buffer+is,data,
- iLBCenc_inst->blockl*sizeof(float));
- /* No lookahead, last window is asymmetric */
- for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
- is = LPC_LOOKBACK;
- if (k < (iLBCenc_inst->lpc_n - 1)) {
- window(temp, lpc_winTbl,
- iLBCenc_inst->lpc_buffer, BLOCKL_MAX);
- } else {
- window(temp, lpc_asymwinTbl,
- iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX);
- }
- autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER);
- window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1);
- levdurb(lp, temp, r, LPC_FILTERORDER);
- bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1);
- a2lsf(lsf + k*LPC_FILTERORDER, lp2);
- }
- is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
- memmove(iLBCenc_inst->lpc_buffer,
- iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is,
- is*sizeof(float));
- }
- /*----------------------------------------------------------------*
- Andersen, et al. Experimental [Page 168]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- * lsf interpolator and conversion from lsf to a coefficients
- * (subrutine to SimpleInterpolateLSF)
- *---------------------------------------------------------------*/
- void LSFinterpolate2a_enc(
- float *a, /* (o) lpc coefficients */
- float *lsf1,/* (i) first set of lsf coefficients */
- float *lsf2,/* (i) second set of lsf coefficients */
- float coef, /* (i) weighting coefficient to use between
- lsf1 and lsf2 */
- long length /* (i) length of coefficient vectors */
- ){
- float lsftmp[LPC_FILTERORDER];
- interpolate(lsftmp, lsf1, lsf2, coef, length);
- lsf2a(a, lsftmp);
- }
- /*----------------------------------------------------------------*
- * lsf interpolator (subrutine to LPCencode)
- *---------------------------------------------------------------*/
- void SimpleInterpolateLSF(
- float *syntdenum, /* (o) the synthesis filter denominator
- resulting from the quantized
- interpolated lsf */
- float *weightdenum, /* (o) the weighting filter denominator
- resulting from the unquantized
- interpolated lsf */
- float *lsf, /* (i) the unquantized lsf coefficients */
- float *lsfdeq, /* (i) the dequantized lsf coefficients */
- float *lsfold, /* (i) the unquantized lsf coefficients of
- the previous signal frame */
- float *lsfdeqold, /* (i) the dequantized lsf coefficients of
- the previous signal frame */
- int length, /* (i) should equate LPC_FILTERORDER */
- iLBC_Enc_Inst_t *iLBCenc_inst
- /* (i/o) the encoder state structure */
- ){
- int i, pos, lp_length;
- float lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2;
- lsf2 = lsf + length;
- lsfdeq2 = lsfdeq + length;
- lp_length = length + 1;
- if (iLBCenc_inst->mode==30) {
- /* sub-frame 1: Interpolation between old and first
- Andersen, et al. Experimental [Page 169]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- set of lsf coefficients */
- LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
- lsf_weightTbl_30ms[0], length);
- memcpy(syntdenum,lp,lp_length*sizeof(float));
- LSFinterpolate2a_enc(lp, lsfold, lsf,
- lsf_weightTbl_30ms[0], length);
- bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length);
- /* sub-frame 2 to 6: Interpolation between first
- and second set of lsf coefficients */
- pos = lp_length;
- for (i = 1; i < iLBCenc_inst->nsub; i++) {
- LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2,
- lsf_weightTbl_30ms[i], length);
- memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
- LSFinterpolate2a_enc(lp, lsf, lsf2,
- lsf_weightTbl_30ms[i], length);
- bwexpand(weightdenum + pos, lp,
- LPC_CHIRP_WEIGHTDENUM, lp_length);
- pos += lp_length;
- }
- }
- else {
- pos = 0;
- for (i = 0; i < iLBCenc_inst->nsub; i++) {
- LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
- lsf_weightTbl_20ms[i], length);
- memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
- LSFinterpolate2a_enc(lp, lsfold, lsf,
- lsf_weightTbl_20ms[i], length);
- bwexpand(weightdenum+pos, lp,
- LPC_CHIRP_WEIGHTDENUM, lp_length);
- pos += lp_length;
- }
- }
- /* update memory */
- if (iLBCenc_inst->mode==30) {
- memcpy(lsfold, lsf2, length*sizeof(float));
- memcpy(lsfdeqold, lsfdeq2, length*sizeof(float));
- }
- else {
- memcpy(lsfold, lsf, length*sizeof(float));
- memcpy(lsfdeqold, lsfdeq, length*sizeof(float));
- Andersen, et al. Experimental [Page 170]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- }
- }
- /*----------------------------------------------------------------*
- * lsf quantizer (subrutine to LPCencode)
- *---------------------------------------------------------------*/
- void SimplelsfQ(
- float *lsfdeq, /* (o) dequantized lsf coefficients
- (dimension FILTERORDER) */
- int *index, /* (o) quantization index */
- float *lsf, /* (i) the lsf coefficient vector to be
- quantized (dimension FILTERORDER ) */
- int lpc_n /* (i) number of lsf sets to quantize */
- ){
- /* Quantize first LSF with memoryless split VQ */
- SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT,
- dim_lsfCbTbl, size_lsfCbTbl);
- if (lpc_n==2) {
- /* Quantize second LSF with memoryless split VQ */
- SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT,
- lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT,
- dim_lsfCbTbl, size_lsfCbTbl);
- }
- }
- /*----------------------------------------------------------------*
- * lpc encoder
- *---------------------------------------------------------------*/
- void LPCencode(
- float *syntdenum, /* (i/o) synthesis filter coefficients
- before/after encoding */
- float *weightdenum, /* (i/o) weighting denumerator
- coefficients before/after
- encoding */
- int *lsf_index, /* (o) lsf quantization index */
- float *data, /* (i) lsf coefficients to quantize */
- iLBC_Enc_Inst_t *iLBCenc_inst
- /* (i/o) the encoder state structure */
- ){
- float lsf[LPC_FILTERORDER * LPC_N_MAX];
- float lsfdeq[LPC_FILTERORDER * LPC_N_MAX];
- int change=0;
- SimpleAnalysis(lsf, data, iLBCenc_inst);
- SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n);
- Andersen, et al. Experimental [Page 171]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- change=LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n);
- SimpleInterpolateLSF(syntdenum, weightdenum,
- lsf, lsfdeq, iLBCenc_inst->lsfold,
- iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst);
- }
- A.39. lsf.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- lsf.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_LSF_H
- #define __iLBC_LSF_H
- void a2lsf(
- float *freq,/* (o) lsf coefficients */
- float *a /* (i) lpc coefficients */
- );
- void lsf2a(
- float *a_coef, /* (o) lpc coefficients */
- float *freq /* (i) lsf coefficients */
- );
- #endif
- A.40. lsf.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- lsf.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <string.h>
- Andersen, et al. Experimental [Page 172]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- #include <math.h>
- #include "iLBC_define.h"
- /*----------------------------------------------------------------*
- * conversion from lpc coefficients to lsf coefficients
- *---------------------------------------------------------------*/
- void a2lsf(
- float *freq,/* (o) lsf coefficients */
- float *a /* (i) lpc coefficients */
- ){
- float steps[LSF_NUMBER_OF_STEPS] =
- {(float)0.00635, (float)0.003175, (float)0.0015875,
- (float)0.00079375};
- float step;
- int step_idx;
- int lsp_index;
- float p[LPC_HALFORDER];
- float q[LPC_HALFORDER];
- float p_pre[LPC_HALFORDER];
- float q_pre[LPC_HALFORDER];
- float old_p, old_q, *old;
- float *pq_coef;
- float omega, old_omega;
- int i;
- float hlp, hlp1, hlp2, hlp3, hlp4, hlp5;
- for (i=0; i<LPC_HALFORDER; i++) {
- p[i] = (float)-1.0 * (a[i + 1] + a[LPC_FILTERORDER - i]);
- q[i] = a[LPC_FILTERORDER - i] - a[i + 1];
- }
- p_pre[0] = (float)-1.0 - p[0];
- p_pre[1] = - p_pre[0] - p[1];
- p_pre[2] = - p_pre[1] - p[2];
- p_pre[3] = - p_pre[2] - p[3];
- p_pre[4] = - p_pre[3] - p[4];
- p_pre[4] = p_pre[4] / 2;
- q_pre[0] = (float)1.0 - q[0];
- q_pre[1] = q_pre[0] - q[1];
- q_pre[2] = q_pre[1] - q[2];
- q_pre[3] = q_pre[2] - q[3];
- q_pre[4] = q_pre[3] - q[4];
- q_pre[4] = q_pre[4] / 2;
- omega = 0.0;
- Andersen, et al. Experimental [Page 173]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- old_omega = 0.0;
- old_p = FLOAT_MAX;
- old_q = FLOAT_MAX;
- /* Here we loop through lsp_index to find all the
- LPC_FILTERORDER roots for omega. */
- for (lsp_index = 0; lsp_index<LPC_FILTERORDER; lsp_index++) {
- /* Depending on lsp_index being even or odd, we
- alternatively solve the roots for the two LSP equations. */
- if ((lsp_index & 0x1) == 0) {
- pq_coef = p_pre;
- old = &old_p;
- } else {
- pq_coef = q_pre;
- old = &old_q;
- }
- /* Start with low resolution grid */
- for (step_idx = 0, step = steps[step_idx];
- step_idx < LSF_NUMBER_OF_STEPS;){
- /* cos(10piw) + pq(0)cos(8piw) + pq(1)cos(6piw) +
- pq(2)cos(4piw) + pq(3)cod(2piw) + pq(4) */
- hlp = (float)cos(omega * TWO_PI);
- hlp1 = (float)2.0 * hlp + pq_coef[0];
- hlp2 = (float)2.0 * hlp * hlp1 - (float)1.0 +
- pq_coef[1];
- hlp3 = (float)2.0 * hlp * hlp2 - hlp1 + pq_coef[2];
- hlp4 = (float)2.0 * hlp * hlp3 - hlp2 + pq_coef[3];
- hlp5 = hlp * hlp4 - hlp3 + pq_coef[4];
- if (((hlp5 * (*old)) <= 0.0) || (omega >= 0.5)){
- if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){
- if (fabs(hlp5) >= fabs(*old)) {
- freq[lsp_index] = omega - step;
- } else {
- freq[lsp_index] = omega;
- }
- Andersen, et al. Experimental [Page 174]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- if ((*old) >= 0.0){
- *old = (float)-1.0 * FLOAT_MAX;
- } else {
- *old = FLOAT_MAX;
- }
- omega = old_omega;
- step_idx = 0;
- step_idx = LSF_NUMBER_OF_STEPS;
- } else {
- if (step_idx == 0) {
- old_omega = omega;
- }
- step_idx++;
- omega -= steps[step_idx];
- /* Go back one grid step */
- step = steps[step_idx];
- }
- } else {
- /* increment omega until they are of different sign,
- and we know there is at least one root between omega
- and old_omega */
- *old = hlp5;
- omega += step;
- }
- }
- }
- for (i = 0; i<LPC_FILTERORDER; i++) {
- freq[i] = freq[i] * TWO_PI;
- }
- }
- /*----------------------------------------------------------------*
- * conversion from lsf coefficients to lpc coefficients
- *---------------------------------------------------------------*/
- void lsf2a(
- float *a_coef, /* (o) lpc coefficients */
- float *freq /* (i) lsf coefficients */
- Andersen, et al. Experimental [Page 175]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- ){
- int i, j;
- float hlp;
- float p[LPC_HALFORDER], q[LPC_HALFORDER];
- float a[LPC_HALFORDER + 1], a1[LPC_HALFORDER],
- a2[LPC_HALFORDER];
- float b[LPC_HALFORDER + 1], b1[LPC_HALFORDER],
- b2[LPC_HALFORDER];
- for (i=0; i<LPC_FILTERORDER; i++) {
- freq[i] = freq[i] * PI2;
- }
- /* Check input for ill-conditioned cases. This part is not
- found in the TIA standard. It involves the following 2 IF
- blocks. If "freq" is judged ill-conditioned, then we first
- modify freq[0] and freq[LPC_HALFORDER-1] (normally
- LPC_HALFORDER = 10 for LPC applications), then we adjust
- the other "freq" values slightly */
- if ((freq[0] <= 0.0) || (freq[LPC_FILTERORDER - 1] >= 0.5)){
- if (freq[0] <= 0.0) {
- freq[0] = (float)0.022;
- }
- if (freq[LPC_FILTERORDER - 1] >= 0.5) {
- freq[LPC_FILTERORDER - 1] = (float)0.499;
- }
- hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) /
- (float) (LPC_FILTERORDER - 1);
- for (i=1; i<LPC_FILTERORDER; i++) {
- freq[i] = freq[i - 1] + hlp;
- }
- }
- memset(a1, 0, LPC_HALFORDER*sizeof(float));
- memset(a2, 0, LPC_HALFORDER*sizeof(float));
- memset(b1, 0, LPC_HALFORDER*sizeof(float));
- memset(b2, 0, LPC_HALFORDER*sizeof(float));
- memset(a, 0, (LPC_HALFORDER+1)*sizeof(float));
- memset(b, 0, (LPC_HALFORDER+1)*sizeof(float));
- Andersen, et al. Experimental [Page 176]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* p[i] and q[i] compute cos(2*pi*omega_{2j}) and
- cos(2*pi*omega_{2j-1} in eqs. 4.2.2.2-1 and 4.2.2.2-2.
- Note that for this code p[i] specifies the coefficients
- used in .Q_A(z) while q[i] specifies the coefficients used
- in .P_A(z) */
- for (i=0; i<LPC_HALFORDER; i++) {
- p[i] = (float)cos(TWO_PI * freq[2 * i]);
- q[i] = (float)cos(TWO_PI * freq[2 * i + 1]);
- }
- a[0] = 0.25;
- b[0] = 0.25;
- for (i= 0; i<LPC_HALFORDER; i++) {
- a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
- b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
- a2[i] = a1[i];
- a1[i] = a[i];
- b2[i] = b1[i];
- b1[i] = b[i];
- }
- for (j=0; j<LPC_FILTERORDER; j++) {
- if (j == 0) {
- a[0] = 0.25;
- b[0] = -0.25;
- } else {
- a[0] = b[0] = 0.0;
- }
- for (i=0; i<LPC_HALFORDER; i++) {
- a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
- b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
- a2[i] = a1[i];
- a1[i] = a[i];
- b2[i] = b1[i];
- b1[i] = b[i];
- }
- a_coef[j + 1] = 2 * (a[LPC_HALFORDER] + b[LPC_HALFORDER]);
- }
- a_coef[0] = 1.0;
- }
- Andersen, et al. Experimental [Page 177]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.41. packing.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- packing.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __PACKING_H
- #define __PACKING_H
- void packsplit(
- int *index, /* (i) the value to split */
- int *firstpart, /* (o) the value specified by most
- significant bits */
- int *rest, /* (o) the value specified by least
- significant bits */
- int bitno_firstpart, /* (i) number of bits in most
- significant part */
- int bitno_total /* (i) number of bits in full range
- of value */
- );
- void packcombine(
- int *index, /* (i/o) the msb value in the
- combined value out */
- int rest, /* (i) the lsb value */
- int bitno_rest /* (i) the number of bits in the
- lsb part */
- );
- void dopack(
- unsigned char **bitstream, /* (i/o) on entrance pointer to
- place in bitstream to pack
- new data, on exit pointer
- to place in bitstream to
- pack future data */
- int index, /* (i) the value to pack */
- int bitno, /* (i) the number of bits that the
- value will fit within */
- int *pos /* (i/o) write position in the
- current byte */
- );
- Andersen, et al. Experimental [Page 178]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- void unpack(
- unsigned char **bitstream, /* (i/o) on entrance pointer to
- place in bitstream to
- unpack new data from, on
- exit pointer to place in
- bitstream to unpack future
- data from */
- int *index, /* (o) resulting value */
- int bitno, /* (i) number of bits used to
- represent the value */
- int *pos /* (i/o) read position in the
- current byte */
- );
- #endif
- A.42. packing.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- packing.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <stdlib.h>
- #include "iLBC_define.h"
- #include "constants.h"
- #include "helpfun.h"
- #include "string.h"
- /*----------------------------------------------------------------*
- * splitting an integer into first most significant bits and
- * remaining least significant bits
- *---------------------------------------------------------------*/
- void packsplit(
- int *index, /* (i) the value to split */
- int *firstpart, /* (o) the value specified by most
- significant bits */
- int *rest, /* (o) the value specified by least
- significant bits */
- Andersen, et al. Experimental [Page 179]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- int bitno_firstpart, /* (i) number of bits in most
- significant part */
- int bitno_total /* (i) number of bits in full range
- of value */
- ){
- int bitno_rest = bitno_total-bitno_firstpart;
- *firstpart = *index>>(bitno_rest);
- *rest = *index-(*firstpart<<(bitno_rest));
- }
- /*----------------------------------------------------------------*
- * combining a value corresponding to msb's with a value
- * corresponding to lsb's
- *---------------------------------------------------------------*/
- void packcombine(
- int *index, /* (i/o) the msb value in the
- combined value out */
- int rest, /* (i) the lsb value */
- int bitno_rest /* (i) the number of bits in the
- lsb part */
- ){
- *index = *index<<bitno_rest;
- *index += rest;
- }
- /*----------------------------------------------------------------*
- * packing of bits into bitstream, i.e., vector of bytes
- *---------------------------------------------------------------*/
- void dopack(
- unsigned char **bitstream, /* (i/o) on entrance pointer to
- place in bitstream to pack
- new data, on exit pointer
- to place in bitstream to
- pack future data */
- int index, /* (i) the value to pack */
- int bitno, /* (i) the number of bits that the
- value will fit within */
- int *pos /* (i/o) write position in the
- current byte */
- ){
- int posLeft;
- /* Clear the bits before starting in a new byte */
- if ((*pos)==0) {
- Andersen, et al. Experimental [Page 180]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- **bitstream=0;
- }
- while (bitno>0) {
- /* Jump to the next byte if end of this byte is reached*/
- if (*pos==8) {
- *pos=0;
- (*bitstream)++;
- **bitstream=0;
- }
- posLeft=8-(*pos);
- /* Insert index into the bitstream */
- if (bitno <= posLeft) {
- **bitstream |= (unsigned char)(index<<(posLeft-bitno));
- *pos+=bitno;
- bitno=0;
- } else {
- **bitstream |= (unsigned char)(index>>(bitno-posLeft));
- *pos=8;
- index-=((index>>(bitno-posLeft))<<(bitno-posLeft));
- bitno-=posLeft;
- }
- }
- }
- /*----------------------------------------------------------------*
- * unpacking of bits from bitstream, i.e., vector of bytes
- *---------------------------------------------------------------*/
- void unpack(
- unsigned char **bitstream, /* (i/o) on entrance pointer to
- place in bitstream to
- unpack new data from, on
- exit pointer to place in
- bitstream to unpack future
- data from */
- int *index, /* (o) resulting value */
- int bitno, /* (i) number of bits used to
- represent the value */
- int *pos /* (i/o) read position in the
- current byte */
- Andersen, et al. Experimental [Page 181]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- ){
- int BitsLeft;
- *index=0;
- while (bitno>0) {
- /* move forward in bitstream when the end of the
- byte is reached */
- if (*pos==8) {
- *pos=0;
- (*bitstream)++;
- }
- BitsLeft=8-(*pos);
- /* Extract bits to index */
- if (BitsLeft>=bitno) {
- *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno));
- *pos+=bitno;
- bitno=0;
- } else {
- if ((8-bitno)>0) {
- *index+=((((**bitstream)<<(*pos)) & 0xFF)>>
- (8-bitno));
- *pos=8;
- } else {
- *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<<
- (bitno-8));
- *pos=8;
- }
- bitno-=BitsLeft;
- }
- }
- }
- A.43. StateConstructW.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- StateConstructW.h
- Andersen, et al. Experimental [Page 182]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_STATECONSTRUCTW_H
- #define __iLBC_STATECONSTRUCTW_H
- void StateConstructW(
- int idxForMax, /* (i) 6-bit index for the quantization of
- max amplitude */
- int *idxVec, /* (i) vector of quantization indexes */
- float *syntDenum, /* (i) synthesis filter denumerator */
- float *out, /* (o) the decoded state vector */
- int len /* (i) length of a state vector */
- );
- #endif
- A.44. StateConstructW.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- StateConstructW.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "constants.h"
- #include "filter.h"
- /*----------------------------------------------------------------*
- * decoding of the start state
- *---------------------------------------------------------------*/
- void StateConstructW(
- int idxForMax, /* (i) 6-bit index for the quantization of
- max amplitude */
- int *idxVec, /* (i) vector of quantization indexes */
- float *syntDenum, /* (i) synthesis filter denumerator */
- Andersen, et al. Experimental [Page 183]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *out, /* (o) the decoded state vector */
- int len /* (i) length of a state vector */
- ){
- float maxVal, tmpbuf[LPC_FILTERORDER+2*STATE_LEN], *tmp,
- numerator[LPC_FILTERORDER+1];
- float foutbuf[LPC_FILTERORDER+2*STATE_LEN], *fout;
- int k,tmpi;
- /* decoding of the maximum value */
- maxVal = state_frgqTbl[idxForMax];
- maxVal = (float)pow(10,maxVal)/(float)4.5;
- /* initialization of buffers and coefficients */
- memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float));
- memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float));
- for (k=0; k<LPC_FILTERORDER; k++) {
- numerator[k]=syntDenum[LPC_FILTERORDER-k];
- }
- numerator[LPC_FILTERORDER]=syntDenum[0];
- tmp = &tmpbuf[LPC_FILTERORDER];
- fout = &foutbuf[LPC_FILTERORDER];
- /* decoding of the sample values */
- for (k=0; k<len; k++) {
- tmpi = len-1-k;
- /* maxVal = 1/scal */
- tmp[k] = maxVal*state_sq3Tbl[idxVec[tmpi]];
- }
- /* circular convolution with all-pass filter */
- memset(tmp+len, 0, len*sizeof(float));
- ZeroPoleFilter(tmp, numerator, syntDenum, 2*len,
- LPC_FILTERORDER, fout);
- for (k=0;k<len;k++) {
- out[k] = fout[len-1-k]+fout[2*len-1-k];
- }
- }
- Andersen, et al. Experimental [Page 184]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.45. StateSearchW.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- StateSearchW.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_STATESEARCHW_H
- #define __iLBC_STATESEARCHW_H
- void AbsQuantW(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) Encoder instance */
- float *in, /* (i) vector to encode */
- float *syntDenum, /* (i) denominator of synthesis filter */
- float *weightDenum, /* (i) denominator of weighting filter */
- int *out, /* (o) vector of quantizer indexes */
- int len, /* (i) length of vector to encode and
- vector of quantizer indexes */
- int state_first /* (i) position of start state in the
- 80 vec */
- );
- void StateSearchW(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) Encoder instance */
- float *residual,/* (i) target residual vector */
- float *syntDenum, /* (i) lpc synthesis filter */
- float *weightDenum, /* (i) weighting filter denuminator */
- int *idxForMax, /* (o) quantizer index for maximum
- amplitude */
- int *idxVec, /* (o) vector of quantization indexes */
- int len, /* (i) length of all vectors */
- int state_first /* (i) position of start state in the
- 80 vec */
- );
- #endif
- Andersen, et al. Experimental [Page 185]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.46. StateSearchW.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- StateSearchW.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include <math.h>
- #include <string.h>
- #include "iLBC_define.h"
- #include "constants.h"
- #include "filter.h"
- #include "helpfun.h"
- /*----------------------------------------------------------------*
- * predictive noise shaping encoding of scaled start state
- * (subrutine for StateSearchW)
- *---------------------------------------------------------------*/
- void AbsQuantW(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) Encoder instance */
- float *in, /* (i) vector to encode */
- float *syntDenum, /* (i) denominator of synthesis filter */
- float *weightDenum, /* (i) denominator of weighting filter */
- int *out, /* (o) vector of quantizer indexes */
- int len, /* (i) length of vector to encode and
- vector of quantizer indexes */
- int state_first /* (i) position of start state in the
- 80 vec */
- ){
- float *syntOut;
- float syntOutBuf[LPC_FILTERORDER+STATE_SHORT_LEN_30MS];
- float toQ, xq;
- int n;
- int index;
- /* initialization of buffer for filtering */
- memset(syntOutBuf, 0, LPC_FILTERORDER*sizeof(float));
- Andersen, et al. Experimental [Page 186]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- /* initialization of pointer for filtering */
- syntOut = &syntOutBuf[LPC_FILTERORDER];
- /* synthesis and weighting filters on input */
- if (state_first) {
- AllPoleFilter (in, weightDenum, SUBL, LPC_FILTERORDER);
- } else {
- AllPoleFilter (in, weightDenum,
- iLBCenc_inst->state_short_len-SUBL,
- LPC_FILTERORDER);
- }
- /* encoding loop */
- for (n=0; n<len; n++) {
- /* time update of filter coefficients */
- if ((state_first)&&(n==SUBL)){
- syntDenum += (LPC_FILTERORDER+1);
- weightDenum += (LPC_FILTERORDER+1);
- /* synthesis and weighting filters on input */
- AllPoleFilter (&in[n], weightDenum, len-n,
- LPC_FILTERORDER);
- } else if ((state_first==0)&&
- (n==(iLBCenc_inst->state_short_len-SUBL))) {
- syntDenum += (LPC_FILTERORDER+1);
- weightDenum += (LPC_FILTERORDER+1);
- /* synthesis and weighting filters on input */
- AllPoleFilter (&in[n], weightDenum, len-n,
- LPC_FILTERORDER);
- }
- /* prediction of synthesized and weighted input */
- syntOut[n] = 0.0;
- AllPoleFilter (&syntOut[n], weightDenum, 1,
- LPC_FILTERORDER);
- /* quantization */
- toQ = in[n]-syntOut[n];
- Andersen, et al. Experimental [Page 187]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- sort_sq(&xq, &index, toQ, state_sq3Tbl, 8);
- out[n]=index;
- syntOut[n] = state_sq3Tbl[out[n]];
- /* update of the prediction filter */
- AllPoleFilter(&syntOut[n], weightDenum, 1,
- LPC_FILTERORDER);
- }
- }
- /*----------------------------------------------------------------*
- * encoding of start state
- *---------------------------------------------------------------*/
- void StateSearchW(
- iLBC_Enc_Inst_t *iLBCenc_inst,
- /* (i) Encoder instance */
- float *residual,/* (i) target residual vector */
- float *syntDenum, /* (i) lpc synthesis filter */
- float *weightDenum, /* (i) weighting filter denuminator */
- int *idxForMax, /* (o) quantizer index for maximum
- amplitude */
- int *idxVec, /* (o) vector of quantization indexes */
- int len, /* (i) length of all vectors */
- int state_first /* (i) position of start state in the
- 80 vec */
- ){
- float dtmp, maxVal;
- float tmpbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS];
- float *tmp, numerator[1+LPC_FILTERORDER];
- float foutbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS], *fout;
- int k;
- float qmax, scal;
- /* initialization of buffers and filter coefficients */
- memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float));
- memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float));
- for (k=0; k<LPC_FILTERORDER; k++) {
- numerator[k]=syntDenum[LPC_FILTERORDER-k];
- }
- numerator[LPC_FILTERORDER]=syntDenum[0];
- tmp = &tmpbuf[LPC_FILTERORDER];
- fout = &foutbuf[LPC_FILTERORDER];
- /* circular convolution with the all-pass filter */
- Andersen, et al. Experimental [Page 188]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- memcpy(tmp, residual, len*sizeof(float));
- memset(tmp+len, 0, len*sizeof(float));
- ZeroPoleFilter(tmp, numerator, syntDenum, 2*len,
- LPC_FILTERORDER, fout);
- for (k=0; k<len; k++) {
- fout[k] += fout[k+len];
- }
- /* identification of the maximum amplitude value */
- maxVal = fout[0];
- for (k=1; k<len; k++) {
- if (fout[k]*fout[k] > maxVal*maxVal){
- maxVal = fout[k];
- }
- }
- maxVal=(float)fabs(maxVal);
- /* encoding of the maximum amplitude value */
- if (maxVal < 10.0) {
- maxVal = 10.0;
- }
- maxVal = (float)log10(maxVal);
- sort_sq(&dtmp, idxForMax, maxVal, state_frgqTbl, 64);
- /* decoding of the maximum amplitude representation value,
- and corresponding scaling of start state */
- maxVal=state_frgqTbl[*idxForMax];
- qmax = (float)pow(10,maxVal);
- scal = (float)(4.5)/qmax;
- for (k=0; k<len; k++){
- fout[k] *= scal;
- }
- /* predictive noise shaping encoding of scaled start state */
- AbsQuantW(iLBCenc_inst, fout,syntDenum,
- weightDenum,idxVec, len, state_first);
- }
- Andersen, et al. Experimental [Page 189]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- A.47. syntFilter.h
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- syntFilter.h
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #ifndef __iLBC_SYNTFILTER_H
- #define __iLBC_SYNTFILTER_H
- void syntFilter(
- float *Out, /* (i/o) Signal to be filtered */
- float *a, /* (i) LP parameters */
- int len, /* (i) Length of signal */
- float *mem /* (i/o) Filter state */
- );
- #endif
- A.48. syntFilter.c
- /******************************************************************
- iLBC Speech Coder ANSI-C Source Code
- syntFilter.c
- Copyright (C) The Internet Society (2004).
- All Rights Reserved.
- ******************************************************************/
- #include "iLBC_define.h"
- /*----------------------------------------------------------------*
- * LP synthesis filter.
- *---------------------------------------------------------------*/
- void syntFilter(
- float *Out, /* (i/o) Signal to be filtered */
- float *a, /* (i) LP parameters */
- int len, /* (i) Length of signal */
- Andersen, et al. Experimental [Page 190]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- float *mem /* (i/o) Filter state */
- ){
- int i, j;
- float *po, *pi, *pa, *pm;
- po=Out;
- /* Filter first part using memory from past */
- for (i=0; i<LPC_FILTERORDER; i++) {
- pi=&Out[i-1];
- pa=&a[1];
- pm=&mem[LPC_FILTERORDER-1];
- for (j=1; j<=i; j++) {
- *po-=(*pa++)*(*pi--);
- }
- for (j=i+1; j<LPC_FILTERORDER+1; j++) {
- *po-=(*pa++)*(*pm--);
- }
- po++;
- }
- /* Filter last part where the state is entirely in
- the output vector */
- for (i=LPC_FILTERORDER; i<len; i++) {
- pi=&Out[i-1];
- pa=&a[1];
- for (j=1; j<LPC_FILTERORDER+1; j++) {
- *po-=(*pa++)*(*pi--);
- }
- po++;
- }
- /* Update state vector */
- memcpy(mem, &Out[len-LPC_FILTERORDER],
- LPC_FILTERORDER*sizeof(float));
- }
- Andersen, et al. Experimental [Page 191]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Authors' Addresses
- Soren Vang Andersen
- Department of Communication Technology
- Aalborg University
- Fredrik Bajers Vej 7A
- 9200 Aalborg
- Denmark
- Phone: ++45 9 6358627
- EMail: sva@kom.auc.dk
- Alan Duric
- Telio AS
- Stoperigt. 2
- Oslo, N-0250
- Norway
- Phone: +47 21673555
- EMail: alan.duric@telio.no
- Henrik Astrom
- Global IP Sound AB
- Olandsgatan 42
- Stockholm, S-11663
- Sweden
- Phone: +46 8 54553040
- EMail: henrik.astrom@globalipsound.com
- Roar Hagen
- Global IP Sound AB
- Olandsgatan 42
- Stockholm, S-11663
- Sweden
- Phone: +46 8 54553040
- EMail: roar.hagen@globalipsound.com
- Andersen, et al. Experimental [Page 192]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- W. Bastiaan Kleijn
- Global IP Sound AB
- Olandsgatan 42
- Stockholm, S-11663
- Sweden
- Phone: +46 8 54553040
- EMail: bastiaan.kleijn@globalipsound.com
- Jan Linden
- Global IP Sound Inc.
- 900 Kearny Street, suite 500
- San Francisco, CA-94133
- USA
- Phone: +1 415 397 2555
- EMail: jan.linden@globalipsound.com
- Andersen, et al. Experimental [Page 193]
- RFC 3951 Internet Low Bit Rate Codec December 2004
- Full Copyright Statement
- Copyright (C) The Internet Society (2004).
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
- Intellectual Property
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the IETF's procedures with respect to rights in IETF Documents can
- be found in BCP 78 and BCP 79.
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at ietf-
- ipr@ietf.org.
- Acknowledgement
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
- Andersen, et al. Experimental [Page 194]
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