rational.h 3.9 KB

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  1. /*
  2. * rational numbers
  3. * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
  4. *
  5. * This file is part of FFmpeg.
  6. *
  7. * FFmpeg is free software; you can redistribute it and/or
  8. * modify it under the terms of the GNU Lesser General Public
  9. * License as published by the Free Software Foundation; either
  10. * version 2.1 of the License, or (at your option) any later version.
  11. *
  12. * FFmpeg is distributed in the hope that it will be useful,
  13. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15. * Lesser General Public License for more details.
  16. *
  17. * You should have received a copy of the GNU Lesser General Public
  18. * License along with FFmpeg; if not, write to the Free Software
  19. * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20. */
  21. /**
  22. * @file
  23. * rational numbers
  24. * @author Michael Niedermayer <michaelni@gmx.at>
  25. */
  26. #ifndef AVUTIL_RATIONAL_H
  27. #define AVUTIL_RATIONAL_H
  28. #include <stdint.h>
  29. #include <limits.h>
  30. #include "attributes.h"
  31. /**
  32. * @addtogroup lavu_math
  33. * @{
  34. */
  35. /**
  36. * rational number numerator/denominator
  37. */
  38. typedef struct AVRational {
  39. int num; ///< numerator
  40. int den; ///< denominator
  41. } AVRational;
  42. /**
  43. * Compare two rationals.
  44. * @param a first rational
  45. * @param b second rational
  46. * @return 0 if a==b, 1 if a>b, -1 if a<b, and INT_MIN if one of the
  47. * values is of the form 0/0
  48. */
  49. static inline int av_cmp_q(AVRational a, AVRational b)
  50. {
  51. const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
  52. if(tmp) {
  53. return ((tmp ^ a.den ^ b.den)>>63)|1;
  54. }
  55. else if(b.den && a.den) {
  56. return 0;
  57. }
  58. else if(a.num && b.num) {
  59. return (a.num>>31) - (b.num>>31);
  60. }
  61. else {
  62. return INT_MIN;
  63. }
  64. }
  65. /**
  66. * Convert rational to double.
  67. * @param a rational to convert
  68. * @return (double) a
  69. */
  70. static inline double av_q2d(AVRational a)
  71. {
  72. return a.num / (double) a.den;
  73. }
  74. /**
  75. * Reduce a fraction.
  76. * This is useful for framerate calculations.
  77. * @param dst_num destination numerator
  78. * @param dst_den destination denominator
  79. * @param num source numerator
  80. * @param den source denominator
  81. * @param max the maximum allowed for dst_num & dst_den
  82. * @return 1 if exact, 0 otherwise
  83. */
  84. int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);
  85. /**
  86. * Multiply two rationals.
  87. * @param b first rational
  88. * @param c second rational
  89. * @return b*c
  90. */
  91. AVRational av_mul_q(AVRational b, AVRational c) av_const;
  92. /**
  93. * Divide one rational by another.
  94. * @param b first rational
  95. * @param c second rational
  96. * @return b/c
  97. */
  98. AVRational av_div_q(AVRational b, AVRational c) av_const;
  99. /**
  100. * Add two rationals.
  101. * @param b first rational
  102. * @param c second rational
  103. * @return b+c
  104. */
  105. AVRational av_add_q(AVRational b, AVRational c) av_const;
  106. /**
  107. * Subtract one rational from another.
  108. * @param b first rational
  109. * @param c second rational
  110. * @return b-c
  111. */
  112. AVRational av_sub_q(AVRational b, AVRational c) av_const;
  113. /**
  114. * Invert a rational.
  115. * @param q value
  116. * @return 1 / q
  117. */
  118. static av_always_inline AVRational av_inv_q(AVRational q)
  119. {
  120. AVRational r = { q.den, q.num };
  121. return r;
  122. }
  123. /**
  124. * Convert a double precision floating point number to a rational.
  125. * inf is expressed as {1,0} or {-1,0} depending on the sign.
  126. *
  127. * @param d double to convert
  128. * @param max the maximum allowed numerator and denominator
  129. * @return (AVRational) d
  130. */
  131. AVRational av_d2q(double d, int max) av_const;
  132. /**
  133. * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
  134. * than q1, 0 if they have the same distance.
  135. */
  136. int av_nearer_q(AVRational q, AVRational q1, AVRational q2);
  137. /**
  138. * Find the nearest value in q_list to q.
  139. * @param q_list an array of rationals terminated by {0, 0}
  140. * @return the index of the nearest value found in the array
  141. */
  142. int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);
  143. /**
  144. * @}
  145. */
  146. #endif /* AVUTIL_RATIONAL_H */