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151 lines
5.1 KiB
151 lines
5.1 KiB
<refentry>
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<refmeta>
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<refentrytitle>V4L2_PIX_FMT_NV12 ('NV12'), V4L2_PIX_FMT_NV21 ('NV21')</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-NV12"><constant>V4L2_PIX_FMT_NV12</constant></refname>
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<refname id="V4L2-PIX-FMT-NV21"><constant>V4L2_PIX_FMT_NV21</constant></refname>
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<refpurpose>Formats with ½ horizontal and vertical
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chroma resolution, also known as YUV 4:2:0. One luminance and one
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chrominance plane with alternating chroma samples as opposed to
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<constant>V4L2_PIX_FMT_YVU420</constant></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 two-plane versions of the YUV 4:2:0 format.
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The three components are separated into two sub-images or planes. The
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Y plane is first. The Y plane has one byte per pixel. For
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<constant>V4L2_PIX_FMT_NV12</constant>, a combined CbCr plane
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immediately follows the Y plane in memory. The CbCr plane is the same
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width, in bytes, as the Y plane (and of the image), but is half as
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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>.
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<constant>V4L2_PIX_FMT_NV21</constant> is the same except the Cb and
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Cr bytes are swapped, the CrCb plane starts with a Cr byte.</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_NV12</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>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>start + 20:</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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