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- <refentry id="V4L2-PIX-FMT-YUV420M">
- <refmeta>
- <refentrytitle>V4L2_PIX_FMT_YUV420M ('YM12')</refentrytitle>
- &manvol;
- </refmeta>
- <refnamediv>
- <refname> <constant>V4L2_PIX_FMT_YUV420M</constant></refname>
- <refpurpose>Variation of <constant>V4L2_PIX_FMT_YUV420</constant>
- with planes non contiguous in memory. </refpurpose>
- </refnamediv>
- <refsect1>
- <title>Description</title>
- <para>This is a multi-planar format, as opposed to a packed format.
- The three components are separated into three sub- images or planes.
- The Y plane is first. The Y plane has one byte per pixel. The Cb data
- constitutes the second plane which is half the width and half
- the height of the Y plane (and of the image). Each Cb belongs to four
- pixels, a two-by-two square of the image. For example,
- Cb<subscript>0</subscript> belongs to Y'<subscript>00</subscript>,
- Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and
- Y'<subscript>11</subscript>. The Cr data, just like the Cb plane, is
- in the third plane. </para>
- <para>If the Y plane has pad bytes after each row, then the Cb
- and Cr planes have half as many pad bytes after their rows. In other
- words, two Cx rows (including padding) is exactly as long as one Y row
- (including padding).</para>
- <para><constant>V4L2_PIX_FMT_YUV420M</constant> is intended to be
- used only in drivers and applications that support the multi-planar API,
- described in <xref linkend="planar-apis"/>. </para>
- <example>
- <title><constant>V4L2_PIX_FMT_YUV420M</constant> 4 × 4
- pixel image</title>
- <formalpara>
- <title>Byte Order.</title>
- <para>Each cell is one byte.
- <informaltable frame="none">
- <tgroup cols="5" align="center">
- <colspec align="left" colwidth="2*" />
- <tbody valign="top">
- <row>
- <entry>start0 + 0:</entry>
- <entry>Y'<subscript>00</subscript></entry>
- <entry>Y'<subscript>01</subscript></entry>
- <entry>Y'<subscript>02</subscript></entry>
- <entry>Y'<subscript>03</subscript></entry>
- </row>
- <row>
- <entry>start0 + 4:</entry>
- <entry>Y'<subscript>10</subscript></entry>
- <entry>Y'<subscript>11</subscript></entry>
- <entry>Y'<subscript>12</subscript></entry>
- <entry>Y'<subscript>13</subscript></entry>
- </row>
- <row>
- <entry>start0 + 8:</entry>
- <entry>Y'<subscript>20</subscript></entry>
- <entry>Y'<subscript>21</subscript></entry>
- <entry>Y'<subscript>22</subscript></entry>
- <entry>Y'<subscript>23</subscript></entry>
- </row>
- <row>
- <entry>start0 + 12:</entry>
- <entry>Y'<subscript>30</subscript></entry>
- <entry>Y'<subscript>31</subscript></entry>
- <entry>Y'<subscript>32</subscript></entry>
- <entry>Y'<subscript>33</subscript></entry>
- </row>
- <row><entry></entry></row>
- <row>
- <entry>start1 + 0:</entry>
- <entry>Cb<subscript>00</subscript></entry>
- <entry>Cb<subscript>01</subscript></entry>
- </row>
- <row>
- <entry>start1 + 2:</entry>
- <entry>Cb<subscript>10</subscript></entry>
- <entry>Cb<subscript>11</subscript></entry>
- </row>
- <row><entry></entry></row>
- <row>
- <entry>start2 + 0:</entry>
- <entry>Cr<subscript>00</subscript></entry>
- <entry>Cr<subscript>01</subscript></entry>
- </row>
- <row>
- <entry>start2 + 2:</entry>
- <entry>Cr<subscript>10</subscript></entry>
- <entry>Cr<subscript>11</subscript></entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- </para>
- </formalpara>
- <formalpara>
- <title>Color Sample Location.</title>
- <para>
- <informaltable frame="none">
- <tgroup cols="7" align="center">
- <tbody valign="top">
- <row>
- <entry></entry>
- <entry>0</entry><entry></entry><entry>1</entry><entry></entry>
- <entry>2</entry><entry></entry><entry>3</entry>
- </row>
- <row>
- <entry>0</entry>
- <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
- <entry>Y</entry><entry></entry><entry>Y</entry>
- </row>
- <row>
- <entry></entry>
- <entry></entry><entry>C</entry><entry></entry><entry></entry>
- <entry></entry><entry>C</entry><entry></entry>
- </row>
- <row>
- <entry>1</entry>
- <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
- <entry>Y</entry><entry></entry><entry>Y</entry>
- </row>
- <row>
- <entry></entry>
- </row>
- <row>
- <entry>2</entry>
- <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
- <entry>Y</entry><entry></entry><entry>Y</entry>
- </row>
- <row>
- <entry></entry>
- <entry></entry><entry>C</entry><entry></entry><entry></entry>
- <entry></entry><entry>C</entry><entry></entry>
- </row>
- <row>
- <entry>3</entry>
- <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
- <entry>Y</entry><entry></entry><entry>Y</entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- </para>
- </formalpara>
- </example>
- </refsect1>
- </refentry>
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