Documentation/DocBook/media/v4l/pixfmt-nv12m.xml

   1     <refentry>
   2       <refmeta>
   3         <refentrytitle>V4L2_PIX_FMT_NV12M ('NM12'), V4L2_PIX_FMT_NV21M ('NM21'), V4L2_PIX_FMT_NV12MT_16X16</refentrytitle>
   4         &manvol;
   5       </refmeta>
   6       <refnamediv>
   7         <refname id="V4L2-PIX-FMT-NV12M"><constant>V4L2_PIX_FMT_NV12M</constant></refname>
   8         <refname id="V4L2-PIX-FMT-NV21M"><constant>V4L2_PIX_FMT_NV21M</constant></refname>
   9         <refname id="V4L2-PIX-FMT-NV12MT-16X16"><constant>V4L2_PIX_FMT_NV12MT_16X16</constant></refname>
  10         <refpurpose>Variation of <constant>V4L2_PIX_FMT_NV12</constant> and <constant>V4L2_PIX_FMT_NV21</constant> with planes
  11           non contiguous in memory. </refpurpose>
  12       </refnamediv>
  13       <refsect1>
  14         <title>Description</title>
  15
  16         <para>This is a multi-planar, two-plane version of the YUV 4:2:0 format.
  17 The three components are separated into two sub-images or planes.
  18 <constant>V4L2_PIX_FMT_NV12M</constant> differs from <constant>V4L2_PIX_FMT_NV12
  19 </constant> in that the two planes are non-contiguous in memory, i.e. the chroma
  20 plane do not necessarily immediately follows the luma plane.
  21 The luminance data occupies the first plane. The Y plane has one byte per pixel.
  22 In the second plane there is a chrominance data with alternating chroma samples.
  23 The CbCr plane is the same width, in bytes, as the Y plane (and of the image),
  24 but is half as tall in pixels. Each CbCr pair belongs to four pixels. For example,
  25 Cb<subscript>0</subscript>/Cr<subscript>0</subscript> belongs to
  26 Y'<subscript>00</subscript>, Y'<subscript>01</subscript>,
  27 Y'<subscript>10</subscript>, Y'<subscript>11</subscript>.
  28 <constant>V4L2_PIX_FMT_NV12MT_16X16</constant> is the tiled version of
  29 <constant>V4L2_PIX_FMT_NV12M</constant> with 16x16 macroblock tiles. Here pixels
  30 are arranged in 16x16 2D tiles and tiles are arranged in linear order in memory.
  31 <constant>V4L2_PIX_FMT_NV21M</constant> is the same as <constant>V4L2_PIX_FMT_NV12M</constant>
  32 except the Cb and Cr bytes are swapped, the CrCb plane starts with a Cr byte.</para>
  33
  34         <para><constant>V4L2_PIX_FMT_NV12M</constant> is intended to be
  35 used only in drivers and applications that support the multi-planar API,
  36 described in <xref linkend="planar-apis"/>. </para>
  37
  38         <para>If the Y plane has pad bytes after each row, then the
  39 CbCr plane has as many pad bytes after its rows.</para>
  40
  41         <example>
  42           <title><constant>V4L2_PIX_FMT_NV12M</constant> 4 &times; 4 pixel image</title>
  43
  44           <formalpara>
  45             <title>Byte Order.</title>
  46             <para>Each cell is one byte.
  47                 <informaltable frame="none">
  48                 <tgroup cols="5" align="center">
  49                   <colspec align="left" colwidth="2*" />
  50                   <tbody valign="top">
  51                     <row>
  52                       <entry>start0&nbsp;+&nbsp;0:</entry>
  53                       <entry>Y'<subscript>00</subscript></entry>
  54                       <entry>Y'<subscript>01</subscript></entry>
  55                       <entry>Y'<subscript>02</subscript></entry>
  56                       <entry>Y'<subscript>03</subscript></entry>
  57                     </row>
  58                     <row>
  59                       <entry>start0&nbsp;+&nbsp;4:</entry>
  60                       <entry>Y'<subscript>10</subscript></entry>
  61                       <entry>Y'<subscript>11</subscript></entry>
  62                       <entry>Y'<subscript>12</subscript></entry>
  63                       <entry>Y'<subscript>13</subscript></entry>
  64                     </row>
  65                     <row>
  66                       <entry>start0&nbsp;+&nbsp;8:</entry>
  67                       <entry>Y'<subscript>20</subscript></entry>
  68                       <entry>Y'<subscript>21</subscript></entry>
  69                       <entry>Y'<subscript>22</subscript></entry>
  70                       <entry>Y'<subscript>23</subscript></entry>
  71                     </row>
  72                     <row>
  73                       <entry>start0&nbsp;+&nbsp;12:</entry>
  74                       <entry>Y'<subscript>30</subscript></entry>
  75                       <entry>Y'<subscript>31</subscript></entry>
  76                       <entry>Y'<subscript>32</subscript></entry>
  77                       <entry>Y'<subscript>33</subscript></entry>
  78                     </row>
  79                     <row>
  80                       <entry></entry>
  81                     </row>
  82                     <row>
  83                       <entry>start1&nbsp;+&nbsp;0:</entry>
  84                       <entry>Cb<subscript>00</subscript></entry>
  85                       <entry>Cr<subscript>00</subscript></entry>
  86                       <entry>Cb<subscript>01</subscript></entry>
  87                       <entry>Cr<subscript>01</subscript></entry>
  88                     </row>
  89                     <row>
  90                       <entry>start1&nbsp;+&nbsp;4:</entry>
  91                       <entry>Cb<subscript>10</subscript></entry>
  92                       <entry>Cr<subscript>10</subscript></entry>
  93                       <entry>Cb<subscript>11</subscript></entry>
  94                       <entry>Cr<subscript>11</subscript></entry>
  95                     </row>
  96                   </tbody>
  97                 </tgroup>
  98                 </informaltable>
  99               </para>
 100           </formalpara>
 101
 102           <formalpara>
 103             <title>Color Sample Location.</title>
 104             <para>
 105                 <informaltable frame="none">
 106                 <tgroup cols="7" align="center">
 107                   <tbody valign="top">
 108                     <row>
 109                       <entry></entry>
 110                       <entry>0</entry><entry></entry><entry>1</entry><entry></entry>
 111                       <entry>2</entry><entry></entry><entry>3</entry>
 112                     </row>
 113                     <row>
 114                       <entry>0</entry>
 115                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 116                       <entry>Y</entry><entry></entry><entry>Y</entry>
 117                     </row>
 118                     <row>
 119                       <entry></entry>
 120                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 121                       <entry></entry><entry>C</entry><entry></entry>
 122                     </row>
 123                     <row>
 124                       <entry>1</entry>
 125                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 126                       <entry>Y</entry><entry></entry><entry>Y</entry>
 127                     </row>
 128                     <row>
 129                       <entry></entry>
 130                     </row>
 131                     <row>
 132                       <entry>2</entry>
 133                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 134                       <entry>Y</entry><entry></entry><entry>Y</entry>
 135                     </row>
 136                     <row>
 137                       <entry></entry>
 138                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 139                       <entry></entry><entry>C</entry><entry></entry>
 140                     </row>
 141                     <row>
 142                       <entry>3</entry>
 143                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 144                       <entry>Y</entry><entry></entry><entry>Y</entry>
 145                     </row>
 146                   </tbody>
 147                 </tgroup>
 148                 </informaltable>
 149               </para>
 150           </formalpara>
 151         </example>
 152       </refsect1>
 153     </refentry>