155 lines
5.2 KiB
XML
155 lines
5.2 KiB
XML
<refentry id="V4L2-PIX-FMT-NV12M">
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<refmeta>
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<refentrytitle>V4L2_PIX_FMT_NV12M ('NV12M')</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname> <constant>V4L2_PIX_FMT_NV12M</constant></refname>
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<refpurpose>Variation of <constant>V4L2_PIX_FMT_NV12</constant> with planes
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non contiguous in memory. </refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>This is a multi-planar, two-plane version of the YUV 4:2:0 format.
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The three components are separated into two sub-images or planes.
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<constant>V4L2_PIX_FMT_NV12M</constant> differs from <constant>V4L2_PIX_FMT_NV12
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</constant> in that the two planes are non-contiguous in memory, i.e. the chroma
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plane do not necessarily immediately follows the luma plane.
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The luminance data occupies the first plane. The Y plane has one byte per pixel.
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In the second plane there is a chrominance data with alternating chroma samples.
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The CbCr plane is the same width, in bytes, as the Y plane (and of the image),
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but is half as tall in pixels. Each CbCr pair belongs to four pixels. For example,
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Cb<subscript>0</subscript>/Cr<subscript>0</subscript> belongs to
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Y'<subscript>00</subscript>, Y'<subscript>01</subscript>,
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Y'<subscript>10</subscript>, Y'<subscript>11</subscript>. </para>
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<para><constant>V4L2_PIX_FMT_NV12M</constant> is intended to be
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used only in drivers and applications that support the multi-planar API,
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described in <xref linkend="planar-apis"/>. </para>
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<para>If the Y plane has pad bytes after each row, then the
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CbCr plane has as many pad bytes after its rows.</para>
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<example>
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<title><constant>V4L2_PIX_FMT_NV12M</constant> 4 × 4 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>start0 + 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>start0 + 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>start0 + 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>start0 + 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></entry>
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</row>
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<row>
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<entry>start1 + 0:</entry>
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<entry>Cb<subscript>00</subscript></entry>
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<entry>Cr<subscript>00</subscript></entry>
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<entry>Cb<subscript>01</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>start1 + 4:</entry>
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<entry>Cb<subscript>10</subscript></entry>
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<entry>Cr<subscript>10</subscript></entry>
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<entry>Cb<subscript>11</subscript></entry>
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<entry>Cr<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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