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Diffstat (limited to 'Documentation/DocBook/v4l/pixfmt-yuv420.xml')
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diff --git a/Documentation/DocBook/v4l/pixfmt-yuv420.xml b/Documentation/DocBook/v4l/pixfmt-yuv420.xml new file mode 100644 index 00000000000..42d7de5e456 --- /dev/null +++ b/Documentation/DocBook/v4l/pixfmt-yuv420.xml @@ -0,0 +1,157 @@ + <refentry> + <refmeta> + <refentrytitle>V4L2_PIX_FMT_YVU420 ('YV12'), V4L2_PIX_FMT_YUV420 ('YU12')</refentrytitle> + &manvol; + </refmeta> + <refnamediv> + <refname id="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></refname> + <refname id="V4L2-PIX-FMT-YUV420"><constant>V4L2_PIX_FMT_YUV420</constant></refname> + <refpurpose>Planar formats with ½ horizontal and +vertical chroma resolution, also known as YUV 4:2:0</refpurpose> + </refnamediv> + <refsect1> + <title>Description</title> + + <para>These are planar formats, 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. For +<constant>V4L2_PIX_FMT_YVU420</constant>, the Cr plane immediately +follows the Y plane in memory. The Cr plane is half the width and half +the height of the Y plane (and of the image). Each Cr belongs to four +pixels, a two-by-two square of the image. For example, +Cr<subscript>0</subscript> belongs to Y'<subscript>00</subscript>, +Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and +Y'<subscript>11</subscript>. Following the Cr plane is the Cb plane, +just like the Cr plane. <constant>V4L2_PIX_FMT_YUV420</constant> is +the same except the Cb plane comes first, then the Cr plane.</para> + + <para>If the Y plane has pad bytes after each row, then the Cr +and Cb 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> + + <example> + <title><constant>V4L2_PIX_FMT_YVU420</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>start + 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>start + 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>start + 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>start + 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>start + 16:</entry> + <entry>Cr<subscript>00</subscript></entry> + <entry>Cr<subscript>01</subscript></entry> + </row> + <row> + <entry>start + 18:</entry> + <entry>Cr<subscript>10</subscript></entry> + <entry>Cr<subscript>11</subscript></entry> + </row> + <row> + <entry>start + 20:</entry> + <entry>Cb<subscript>00</subscript></entry> + <entry>Cb<subscript>01</subscript></entry> + </row> + <row> + <entry>start + 22:</entry> + <entry>Cb<subscript>10</subscript></entry> + <entry>Cb<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> + + <!-- +Local Variables: +mode: sgml +sgml-parent-document: "pixfmt.sgml" +indent-tabs-mode: nil +End: + --> |