158 строки
5.3 KiB
XML
158 строки
5.3 KiB
XML
<refentry>
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<refmeta>
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<refentrytitle>V4L2_PIX_FMT_YVU420 ('YV12'), V4L2_PIX_FMT_YUV420 ('YU12')</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname id="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></refname>
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<refname id="V4L2-PIX-FMT-YUV420"><constant>V4L2_PIX_FMT_YUV420</constant></refname>
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<refpurpose>Planar formats with ½ horizontal and
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vertical chroma resolution, also known as YUV 4:2:0</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>These are planar formats, as opposed to a packed format.
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The three components are separated into three sub- images or planes.
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The Y plane is first. The Y plane has one byte per pixel. For
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<constant>V4L2_PIX_FMT_YVU420</constant>, the Cr plane immediately
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follows the Y plane in memory. The Cr plane is half the width and half
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the height of the Y plane (and of the image). Each Cr belongs to four
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pixels, a two-by-two square of the image. For example,
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Cr<subscript>0</subscript> belongs to Y'<subscript>00</subscript>,
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Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and
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Y'<subscript>11</subscript>. Following the Cr plane is the Cb plane,
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just like the Cr plane. <constant>V4L2_PIX_FMT_YUV420</constant> is
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the same except the Cb plane comes first, then the Cr plane.</para>
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<para>If the Y plane has pad bytes after each row, then the Cr
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and Cb planes have half as many pad bytes after their rows. In other
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words, two Cx rows (including padding) is exactly as long as one Y row
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(including padding).</para>
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<example>
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<title><constant>V4L2_PIX_FMT_YVU420</constant> 4 × 4
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pixel image</title>
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<formalpara>
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<title>Byte Order.</title>
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<para>Each cell is one byte.
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<informaltable frame="none">
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<tgroup cols="5" align="center">
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<colspec align="left" colwidth="2*" />
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<tbody valign="top">
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<row>
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<entry>start + 0:</entry>
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<entry>Y'<subscript>00</subscript></entry>
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<entry>Y'<subscript>01</subscript></entry>
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<entry>Y'<subscript>02</subscript></entry>
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<entry>Y'<subscript>03</subscript></entry>
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</row>
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<row>
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<entry>start + 4:</entry>
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<entry>Y'<subscript>10</subscript></entry>
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<entry>Y'<subscript>11</subscript></entry>
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<entry>Y'<subscript>12</subscript></entry>
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<entry>Y'<subscript>13</subscript></entry>
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</row>
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<row>
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<entry>start + 8:</entry>
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<entry>Y'<subscript>20</subscript></entry>
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<entry>Y'<subscript>21</subscript></entry>
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<entry>Y'<subscript>22</subscript></entry>
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<entry>Y'<subscript>23</subscript></entry>
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</row>
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<row>
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<entry>start + 12:</entry>
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<entry>Y'<subscript>30</subscript></entry>
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<entry>Y'<subscript>31</subscript></entry>
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<entry>Y'<subscript>32</subscript></entry>
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<entry>Y'<subscript>33</subscript></entry>
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</row>
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<row>
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<entry>start + 16:</entry>
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<entry>Cr<subscript>00</subscript></entry>
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<entry>Cr<subscript>01</subscript></entry>
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</row>
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<row>
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<entry>start + 18:</entry>
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<entry>Cr<subscript>10</subscript></entry>
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<entry>Cr<subscript>11</subscript></entry>
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</row>
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<row>
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<entry>start + 20:</entry>
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<entry>Cb<subscript>00</subscript></entry>
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<entry>Cb<subscript>01</subscript></entry>
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</row>
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<row>
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<entry>start + 22:</entry>
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<entry>Cb<subscript>10</subscript></entry>
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<entry>Cb<subscript>11</subscript></entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</formalpara>
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<formalpara>
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<title>Color Sample Location.</title>
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<para>
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<informaltable frame="none">
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<tgroup cols="7" align="center">
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<tbody valign="top">
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<row>
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<entry></entry>
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<entry>0</entry><entry></entry><entry>1</entry><entry></entry>
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<entry>2</entry><entry></entry><entry>3</entry>
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</row>
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<row>
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<entry>0</entry>
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<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
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<entry>Y</entry><entry></entry><entry>Y</entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry><entry>C</entry><entry></entry><entry></entry>
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<entry></entry><entry>C</entry><entry></entry>
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</row>
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<row>
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<entry>1</entry>
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<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
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<entry>Y</entry><entry></entry><entry>Y</entry>
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</row>
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<row>
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<entry></entry>
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</row>
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<row>
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<entry>2</entry>
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<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
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<entry>Y</entry><entry></entry><entry>Y</entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry><entry>C</entry><entry></entry><entry></entry>
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<entry></entry><entry>C</entry><entry></entry>
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</row>
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<row>
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<entry>3</entry>
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<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
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<entry>Y</entry><entry></entry><entry>Y</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</formalpara>
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</example>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "pixfmt.sgml"
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indent-tabs-mode: nil
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End:
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-->
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