| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 1 | <refentry> |
| 2 | <refmeta> |
| 3 | <refentrytitle>V4L2_PIX_FMT_YVU420 ('YV12'), V4L2_PIX_FMT_YUV420 ('YU12')</refentrytitle> |
| 4 | &manvol; |
| 5 | </refmeta> |
| 6 | <refnamediv> |
| 7 | <refname id="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></refname> |
| 8 | <refname id="V4L2-PIX-FMT-YUV420"><constant>V4L2_PIX_FMT_YUV420</constant></refname> |
| 9 | <refpurpose>Planar formats with ½ horizontal and |
| 10 | vertical chroma resolution, also known as YUV 4:2:0</refpurpose> |
| 11 | </refnamediv> |
| 12 | <refsect1> |
| 13 | <title>Description</title> |
| 14 | |
| 15 | <para>These are planar formats, as opposed to a packed format. |
| 16 | The three components are separated into three sub- images or planes. |
| 17 | The Y plane is first. The Y plane has one byte per pixel. For |
| 18 | <constant>V4L2_PIX_FMT_YVU420</constant>, the Cr plane immediately |
| 19 | follows the Y plane in memory. The Cr plane is half the width and half |
| 20 | the height of the Y plane (and of the image). Each Cr belongs to four |
| 21 | pixels, a two-by-two square of the image. For example, |
| 22 | Cr<subscript>0</subscript> belongs to Y'<subscript>00</subscript>, |
| 23 | Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and |
| 24 | Y'<subscript>11</subscript>. Following the Cr plane is the Cb plane, |
| 25 | just like the Cr plane. <constant>V4L2_PIX_FMT_YUV420</constant> is |
| 26 | the same except the Cb plane comes first, then the Cr plane.</para> |
| 27 | |
| 28 | <para>If the Y plane has pad bytes after each row, then the Cr |
| 29 | and Cb planes have half as many pad bytes after their rows. In other |
| 30 | words, two Cx rows (including padding) is exactly as long as one Y row |
| 31 | (including padding).</para> |
| 32 | |
| 33 | <example> |
| 34 | <title><constant>V4L2_PIX_FMT_YVU420</constant> 4 × 4 |
| 35 | 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>start + 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>start + 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>start + 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>start + 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>start + 16:</entry> |
| 74 | <entry>Cr<subscript>00</subscript></entry> |
| 75 | <entry>Cr<subscript>01</subscript></entry> |
| 76 | </row> |
| 77 | <row> |
| 78 | <entry>start + 18:</entry> |
| 79 | <entry>Cr<subscript>10</subscript></entry> |
| 80 | <entry>Cr<subscript>11</subscript></entry> |
| 81 | </row> |
| 82 | <row> |
| 83 | <entry>start + 20:</entry> |
| 84 | <entry>Cb<subscript>00</subscript></entry> |
| 85 | <entry>Cb<subscript>01</subscript></entry> |
| 86 | </row> |
| 87 | <row> |
| 88 | <entry>start + 22:</entry> |
| 89 | <entry>Cb<subscript>10</subscript></entry> |
| 90 | <entry>Cb<subscript>11</subscript></entry> |
| 91 | </row> |
| 92 | </tbody> |
| 93 | </tgroup> |
| 94 | </informaltable> |
| 95 | </para> |
| 96 | </formalpara> |
| 97 | |
| 98 | <formalpara> |
| 99 | <title>Color Sample Location.</title> |
| 100 | <para> |
| 101 | <informaltable frame="none"> |
| 102 | <tgroup cols="7" align="center"> |
| 103 | <tbody valign="top"> |
| 104 | <row> |
| 105 | <entry></entry> |
| 106 | <entry>0</entry><entry></entry><entry>1</entry><entry></entry> |
| 107 | <entry>2</entry><entry></entry><entry>3</entry> |
| 108 | </row> |
| 109 | <row> |
| 110 | <entry>0</entry> |
| 111 | <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> |
| 112 | <entry>Y</entry><entry></entry><entry>Y</entry> |
| 113 | </row> |
| 114 | <row> |
| 115 | <entry></entry> |
| 116 | <entry></entry><entry>C</entry><entry></entry><entry></entry> |
| 117 | <entry></entry><entry>C</entry><entry></entry> |
| 118 | </row> |
| 119 | <row> |
| 120 | <entry>1</entry> |
| 121 | <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> |
| 122 | <entry>Y</entry><entry></entry><entry>Y</entry> |
| 123 | </row> |
| 124 | <row> |
| 125 | <entry></entry> |
| 126 | </row> |
| 127 | <row> |
| 128 | <entry>2</entry> |
| 129 | <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> |
| 130 | <entry>Y</entry><entry></entry><entry>Y</entry> |
| 131 | </row> |
| 132 | <row> |
| 133 | <entry></entry> |
| 134 | <entry></entry><entry>C</entry><entry></entry><entry></entry> |
| 135 | <entry></entry><entry>C</entry><entry></entry> |
| 136 | </row> |
| 137 | <row> |
| 138 | <entry>3</entry> |
| 139 | <entry>Y</entry><entry></entry><entry>Y</entry><entry></entry> |
| 140 | <entry>Y</entry><entry></entry><entry>Y</entry> |
| 141 | </row> |
| 142 | </tbody> |
| 143 | </tgroup> |
| 144 | </informaltable> |
| 145 | </para> |
| 146 | </formalpara> |
| 147 | </example> |
| 148 | </refsect1> |
| 149 | </refentry> |