Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry> 2 <refmeta> 3 <refentrytitle>V4L2_PIX_FMT_YUV420M ('YM12'), V4L2_PIX_FMT_YVU420M ('YM21')</refentrytitle> 4 &manvol; 5 </refmeta> 6 <refnamediv> 7 <refname id="V4L2-PIX-FMT-YUV420M"><constant>V4L2_PIX_FMT_YUV420M</constant></refname> 8 <refname id="V4L2-PIX-FMT-YVU420M"><constant>V4L2_PIX_FMT_YVU420M</constant></refname> 9 <refpurpose>Variation of <constant>V4L2_PIX_FMT_YUV420</constant> and 10 <constant>V4L2_PIX_FMT_YVU420</constant> with planes non contiguous 11 in memory.</refpurpose> 12 </refnamediv> 13 14 <refsect1> 15 <title>Description</title> 16 17 <para>This is a multi-planar format, as opposed to a packed format. 18 The three components are separated into three sub-images or planes.</para> 19 20 <para>The Y plane is first. The Y plane has one byte per pixel. 21 For <constant>V4L2_PIX_FMT_YUV420M</constant> the Cb data 22 constitutes the second plane which is half the width and half 23 the height of the Y plane (and of the image). Each Cb belongs to four 24 pixels, a two-by-two square of the image. For example, 25 Cb<subscript>0</subscript> belongs to Y'<subscript>00</subscript>, 26 Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and 27 Y'<subscript>11</subscript>. The Cr data, just like the Cb plane, is 28 in the third plane.</para> 29 30 <para><constant>V4L2_PIX_FMT_YVU420M</constant> is the same except 31 the Cr data is stored in the second plane and the Cb data in the third plane. 32 </para> 33 34 <para>If the Y plane has pad bytes after each row, then the Cb 35 and Cr planes have half as many pad bytes after their rows. In other 36 words, two Cx rows (including padding) is exactly as long as one Y row 37 (including padding).</para> 38 39 <para><constant>V4L2_PIX_FMT_YUV420M</constant> and 40 <constant>V4L2_PIX_FMT_YVU420M</constant> are intended to be 41 used only in drivers and applications that support the multi-planar API, 42 described in <xref linkend="planar-apis"/>. </para> 43 44 <example> 45 <title><constant>V4L2_PIX_FMT_YUV420M</constant> 4 × 4 46 pixel image</title> 47 48 <formalpara> 49 <title>Byte Order.</title> 50 <para>Each cell is one byte. 51 <informaltable frame="none"> 52 <tgroup cols="5" align="center"> 53 <colspec align="left" colwidth="2*" /> 54 <tbody valign="top"> 55 <row> 56 <entry>start0 + 0:</entry> 57 <entry>Y'<subscript>00</subscript></entry> 58 <entry>Y'<subscript>01</subscript></entry> 59 <entry>Y'<subscript>02</subscript></entry> 60 <entry>Y'<subscript>03</subscript></entry> 61 </row> 62 <row> 63 <entry>start0 + 4:</entry> 64 <entry>Y'<subscript>10</subscript></entry> 65 <entry>Y'<subscript>11</subscript></entry> 66 <entry>Y'<subscript>12</subscript></entry> 67 <entry>Y'<subscript>13</subscript></entry> 68 </row> 69 <row> 70 <entry>start0 + 8:</entry> 71 <entry>Y'<subscript>20</subscript></entry> 72 <entry>Y'<subscript>21</subscript></entry> 73 <entry>Y'<subscript>22</subscript></entry> 74 <entry>Y'<subscript>23</subscript></entry> 75 </row> 76 <row> 77 <entry>start0 + 12:</entry> 78 <entry>Y'<subscript>30</subscript></entry> 79 <entry>Y'<subscript>31</subscript></entry> 80 <entry>Y'<subscript>32</subscript></entry> 81 <entry>Y'<subscript>33</subscript></entry> 82 </row> 83 <row><entry></entry></row> 84 <row> 85 <entry>start1 + 0:</entry> 86 <entry>Cb<subscript>00</subscript></entry> 87 <entry>Cb<subscript>01</subscript></entry> 88 </row> 89 <row> 90 <entry>start1 + 2:</entry> 91 <entry>Cb<subscript>10</subscript></entry> 92 <entry>Cb<subscript>11</subscript></entry> 93 </row> 94 <row><entry></entry></row> 95 <row> 96 <entry>start2 + 0:</entry> 97 <entry>Cr<subscript>00</subscript></entry> 98 <entry>Cr<subscript>01</subscript></entry> 99 </row> 100 <row> 101 <entry>start2 + 2:</entry> 102 <entry>Cr<subscript>10</subscript></entry> 103 <entry>Cr<subscript>11</subscript></entry> 104 </row> 105 </tbody> 106 </tgroup> 107 </informaltable> 108 </para> 109 </formalpara> 110 111 <formalpara> 112 <title>Color Sample Location.</title> 113 <para> 114 <informaltable frame="none"> 115 <tgroup cols="7" align="center"> 116 <tbody valign="top"> 117 <row> 118 <entry></entry> 119 <entry>0</entry><entry></entry><entry>1</entry><entry></entry> 120 <entry>2</entry><entry></entry><entry>3</entry> 121 </row> 122 <row> 123 <entry>0</entry> 124 <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> 125 <entry>Y</entry><entry></entry><entry>Y</entry> 126 </row> 127 <row> 128 <entry></entry> 129 <entry></entry><entry>C</entry><entry></entry><entry></entry> 130 <entry></entry><entry>C</entry><entry></entry> 131 </row> 132 <row> 133 <entry>1</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 </row> 140 <row> 141 <entry>2</entry> 142 <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> 143 <entry>Y</entry><entry></entry><entry>Y</entry> 144 </row> 145 <row> 146 <entry></entry> 147 <entry></entry><entry>C</entry><entry></entry><entry></entry> 148 <entry></entry><entry>C</entry><entry></entry> 149 </row> 150 <row> 151 <entry>3</entry> 152 <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> 153 <entry>Y</entry><entry></entry><entry>Y</entry> 154 </row> 155 </tbody> 156 </tgroup> 157 </informaltable> 158 </para> 159 </formalpara> 160 </example> 161 </refsect1> 162 </refentry>
