Documentation/DocBook/media/v4l/pixfmt-yuv420m.xml

   1     <refentry id="V4L2-PIX-FMT-YUV420M">
   2       <refmeta>
   3         <refentrytitle>V4L2_PIX_FMT_YUV420M ('YU12M')</refentrytitle>
   4         &manvol;
   5       </refmeta>
   6       <refnamediv>
   7         <refname> <constant>V4L2_PIX_FMT_YUV420M</constant></refname>
   8         <refpurpose>Variation of <constant>V4L2_PIX_FMT_YUV420</constant>
   9           with planes non contiguous in memory. </refpurpose>
  10       </refnamediv>
  11
  12       <refsect1>
  13         <title>Description</title>
  14
  15         <para>This is a multi-planar format, as opposed to a packed format.
  16 The three components are separated into three sub- images or planes.
  17
  18 The Y plane is first. The Y plane has one byte per pixel. The Cb data
  19 constitutes the second plane which is half the width and half
  20 the height of the Y plane (and of the image). Each Cb belongs to four
  21 pixels, a two-by-two square of the image. For example,
  22 Cb<subscript>0</subscript> belongs to Y'<subscript>00</subscript>,
  23 Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and
  24 Y'<subscript>11</subscript>. The Cr data, just like the Cb plane, is
  25 in the third plane. </para>
  26
  27         <para>If the Y plane has pad bytes after each row, then the Cb
  28 and Cr planes have half as many pad bytes after their rows. In other
  29 words, two Cx rows (including padding) is exactly as long as one Y row
  30 (including padding).</para>
  31
  32         <para><constant>V4L2_PIX_FMT_NV12M</constant> is intended to be
  33 used only in drivers and applications that support the multi-planar API,
  34 described in <xref linkend="planar-apis"/>. </para>
  35
  36         <example>
  37           <title><constant>V4L2_PIX_FMT_YVU420M</constant> 4 &times; 4
  38 pixel image</title>
  39
  40           <formalpara>
  41             <title>Byte Order.</title>
  42             <para>Each cell is one byte.
  43                 <informaltable frame="none">
  44                 <tgroup cols="5" align="center">
  45                   <colspec align="left" colwidth="2*" />
  46                   <tbody valign="top">
  47                     <row>
  48                       <entry>start0&nbsp;+&nbsp;0:</entry>
  49                       <entry>Y'<subscript>00</subscript></entry>
  50                       <entry>Y'<subscript>01</subscript></entry>
  51                       <entry>Y'<subscript>02</subscript></entry>
  52                       <entry>Y'<subscript>03</subscript></entry>
  53                     </row>
  54                     <row>
  55                       <entry>start0&nbsp;+&nbsp;4:</entry>
  56                       <entry>Y'<subscript>10</subscript></entry>
  57                       <entry>Y'<subscript>11</subscript></entry>
  58                       <entry>Y'<subscript>12</subscript></entry>
  59                       <entry>Y'<subscript>13</subscript></entry>
  60                     </row>
  61                     <row>
  62                       <entry>start0&nbsp;+&nbsp;8:</entry>
  63                       <entry>Y'<subscript>20</subscript></entry>
  64                       <entry>Y'<subscript>21</subscript></entry>
  65                       <entry>Y'<subscript>22</subscript></entry>
  66                       <entry>Y'<subscript>23</subscript></entry>
  67                     </row>
  68                     <row>
  69                       <entry>start0&nbsp;+&nbsp;12:</entry>
  70                       <entry>Y'<subscript>30</subscript></entry>
  71                       <entry>Y'<subscript>31</subscript></entry>
  72                       <entry>Y'<subscript>32</subscript></entry>
  73                       <entry>Y'<subscript>33</subscript></entry>
  74                     </row>
  75                     <row><entry></entry></row>
  76                     <row>
  77                       <entry>start1&nbsp;+&nbsp;0:</entry>
  78                       <entry>Cb<subscript>00</subscript></entry>
  79                       <entry>Cb<subscript>01</subscript></entry>
  80                     </row>
  81                     <row>
  82                       <entry>start1&nbsp;+&nbsp;2:</entry>
  83                       <entry>Cb<subscript>10</subscript></entry>
  84                       <entry>Cb<subscript>11</subscript></entry>
  85                     </row>
  86                     <row><entry></entry></row>
  87                     <row>
  88                       <entry>start2&nbsp;+&nbsp;0:</entry>
  89                       <entry>Cr<subscript>00</subscript></entry>
  90                       <entry>Cr<subscript>01</subscript></entry>
  91                     </row>
  92                     <row>
  93                       <entry>start2&nbsp;+&nbsp;2:</entry>
  94                       <entry>Cr<subscript>10</subscript></entry>
  95                       <entry>Cr<subscript>11</subscript></entry>
  96                     </row>
  97                   </tbody>
  98                 </tgroup>
  99                 </informaltable>
 100               </para>
 101           </formalpara>
 102
 103           <formalpara>
 104             <title>Color Sample Location.</title>
 105             <para>
 106                 <informaltable frame="none">
 107                 <tgroup cols="7" align="center">
 108                   <tbody valign="top">
 109                     <row>
 110                       <entry></entry>
 111                       <entry>0</entry><entry></entry><entry>1</entry><entry></entry>
 112                       <entry>2</entry><entry></entry><entry>3</entry>
 113                     </row>
 114                     <row>
 115                       <entry>0</entry>
 116                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 117                       <entry>Y</entry><entry></entry><entry>Y</entry>
 118                     </row>
 119                     <row>
 120                       <entry></entry>
 121                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 122                       <entry></entry><entry>C</entry><entry></entry>
 123                     </row>
 124                     <row>
 125                       <entry>1</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                     </row>
 132                     <row>
 133                       <entry>2</entry>
 134                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 135                       <entry>Y</entry><entry></entry><entry>Y</entry>
 136                     </row>
 137                     <row>
 138                       <entry></entry>
 139                       <entry></entry><entry>C</entry><entry></entry><entry></entry>
 140                       <entry></entry><entry>C</entry><entry></entry>
 141                     </row>
 142                     <row>
 143                       <entry>3</entry>
 144                       <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
 145                       <entry>Y</entry><entry></entry><entry>Y</entry>
 146                     </row>
 147                   </tbody>
 148                 </tgroup>
 149                 </informaltable>
 150               </para>
 151           </formalpara>
 152         </example>
 153       </refsect1>
 154     </refentry>