Documentation/DocBook/v4l/pixfmt-nv12m.xml

   1     <refentry id="V4L2-PIX-FMT-NV12M">
   2       <refmeta>
   3         <refentrytitle>V4L2_PIX_FMT_NV12M ('NV12M')</refentrytitle>
   4         &manvol;
   5       </refmeta>
   6       <refnamediv>
   7         <refname> <constant>V4L2_PIX_FMT_NV12M</constant></refname>
   8         <refpurpose>Variation of <constant>V4L2_PIX_FMT_NV12</constant> with planes
   9           non contiguous in memory. </refpurpose>
  10       </refnamediv>
  11       <refsect1>
  12         <title>Description</title>
  13
  14         <para>This is a multi-planar, two-plane version of the YUV 4:2:0 format.
  15 The three components are separated into two sub-images or planes.
  16 <constant>V4L2_PIX_FMT_NV12M</constant> differs from <constant>V4L2_PIX_FMT_NV12
  17 </constant> in that the two planes are non-contiguous in memory, i.e. the chroma
  18 plane do not necessarily immediately follows the luma plane.
  19 The luminance data occupies the first plane. The Y plane has one byte per pixel.
  20 In the second plane there is a chrominance data with alternating chroma samples.
  21 The CbCr plane is the same width, in bytes, as the Y plane (and of the image),
  22 but is half as tall in pixels. Each CbCr pair belongs to four pixels. For example,
  23 Cb<subscript>0</subscript>/Cr<subscript>0</subscript> belongs to
  24 Y'<subscript>00</subscript>, Y'<subscript>01</subscript>,
  25 Y'<subscript>10</subscript>, Y'<subscript>11</subscript>. </para>
  26
  27         <para><constant>V4L2_PIX_FMT_NV12M</constant> is intended to be
  28 used only in drivers and applications that support the multi-planar API,
  29 described in <xref linkend="planar-apis"/>. </para>
  30
  31         <para>If the Y plane has pad bytes after each row, then the
  32 CbCr plane has as many pad bytes after its rows.</para>
  33
  34         <example>
  35           <title><constant>V4L2_PIX_FMT_NV12M</constant> 4 &times; 4 pixel image</title>
  36
  37           <formalpara>
  38             <title>Byte Order.</title>
  39             <para>Each cell is one byte.
  40                 <informaltable frame="none">
  41                 <tgroup cols="5" align="center">
  42                   <colspec align="left" colwidth="2*" />
  43                   <tbody valign="top">
  44                     <row>
  45                       <entry>start0&nbsp;+&nbsp;0:</entry>
  46                       <entry>Y'<subscript>00</subscript></entry>
  47                       <entry>Y'<subscript>01</subscript></entry>
  48                       <entry>Y'<subscript>02</subscript></entry>
  49                       <entry>Y'<subscript>03</subscript></entry>
  50                     </row>
  51                     <row>
  52                       <entry>start0&nbsp;+&nbsp;4:</entry>
  53                       <entry>Y'<subscript>10</subscript></entry>
  54                       <entry>Y'<subscript>11</subscript></entry>
  55                       <entry>Y'<subscript>12</subscript></entry>
  56                       <entry>Y'<subscript>13</subscript></entry>
  57                     </row>
  58                     <row>
  59                       <entry>start0&nbsp;+&nbsp;8:</entry>
  60                       <entry>Y'<subscript>20</subscript></entry>
  61                       <entry>Y'<subscript>21</subscript></entry>
  62                       <entry>Y'<subscript>22</subscript></entry>
  63                       <entry>Y'<subscript>23</subscript></entry>
  64                     </row>
  65                     <row>
  66                       <entry>start0&nbsp;+&nbsp;12:</entry>
  67                       <entry>Y'<subscript>30</subscript></entry>
  68                       <entry>Y'<subscript>31</subscript></entry>
  69                       <entry>Y'<subscript>32</subscript></entry>
  70                       <entry>Y'<subscript>33</subscript></entry>
  71                     </row>
  72                     <row>
  73                       <entry></entry>
  74                     </row>
  75                     <row>
  76                       <entry>start1&nbsp;+&nbsp;0:</entry>
  77                       <entry>Cb<subscript>00</subscript></entry>
  78                       <entry>Cr<subscript>00</subscript></entry>
  79                       <entry>Cb<subscript>01</subscript></entry>
  80                       <entry>Cr<subscript>01</subscript></entry>
  81                     </row>
  82                     <row>
  83                       <entry>start1&nbsp;+&nbsp;4:</entry>
  84                       <entry>Cb<subscript>10</subscript></entry>
  85                       <entry>Cr<subscript>10</subscript></entry>
  86                       <entry>Cb<subscript>11</subscript></entry>
  87                       <entry>Cr<subscript>11</subscript></entry>
  88                     </row>
  89                   </tbody>
  90                 </tgroup>
  91                 </informaltable>
  92               </para>
  93           </formalpara>
  94
  95           <formalpara>
  96             <title>Color Sample Location.</title>
  97             <para>
  98                 <informaltable frame="none">
  99                 <tgroup cols="7" align="center">
 100                   <tbody valign="top">
 101                     <row>
 102                       <entry></entry>
 103                       <entry>0</entry><entry></entry><entry>1</entry><entry></entry>
 104                       <entry>2</entry><entry></entry><entry>3</entry>
 105                     </row>
 106                     <row>
 107                       <entry>0</entry>
 108                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 109                       <entry>Y</entry><entry></entry><entry>Y</entry>
 110                     </row>
 111                     <row>
 112                       <entry></entry>
 113                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 114                       <entry></entry><entry>C</entry><entry></entry>
 115                     </row>
 116                     <row>
 117                       <entry>1</entry>
 118                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 119                       <entry>Y</entry><entry></entry><entry>Y</entry>
 120                     </row>
 121                     <row>
 122                       <entry></entry>
 123                     </row>
 124                     <row>
 125                       <entry>2</entry>
 126                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 127                       <entry>Y</entry><entry></entry><entry>Y</entry>
 128                     </row>
 129                     <row>
 130                       <entry></entry>
 131                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 132                       <entry></entry><entry>C</entry><entry></entry>
 133                     </row>
 134                     <row>
 135                       <entry>3</entry>
 136                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 137                       <entry>Y</entry><entry></entry><entry>Y</entry>
 138                     </row>
 139                   </tbody>
 140                 </tgroup>
 141                 </informaltable>
 142               </para>
 143           </formalpara>
 144         </example>
 145       </refsect1>
 146     </refentry>
 147
 148   <!--
 149 Local Variables:
 150 mode: sgml
 151 sgml-parent-document: "pixfmt.sgml"
 152 indent-tabs-mode: nil
 153 End:
 154   -->