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authorMauro Carvalho Chehab <mchehab@redhat.com>2009-09-13 21:16:04 -0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2009-09-18 22:47:55 -0400
commit8e080c2e6cadada82a6b520e0c23a1cb974822d5 (patch)
tree991450ff1abba98e5313906478c33816a202ccab /Documentation/DocBook/v4l/pixfmt-yuv420.xml
parentf4e96deb4513d044653027d4921fd7592195503a (diff)
V4L/DVB (12761): DocBook: add media API specs
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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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 &frac12; horizontal and
10vertical 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.
16The three components are separated into three sub- images or planes.
17The Y plane is first. The Y plane has one byte per pixel. For
18<constant>V4L2_PIX_FMT_YVU420</constant>, the Cr plane immediately
19follows the Y plane in memory. The Cr plane is half the width and half
20the height of the Y plane (and of the image). Each Cr belongs to four
21pixels, a two-by-two square of the image. For example,
22Cr<subscript>0</subscript> belongs to Y'<subscript>00</subscript>,
23Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and
24Y'<subscript>11</subscript>. Following the Cr plane is the Cb plane,
25just like the Cr plane. <constant>V4L2_PIX_FMT_YUV420</constant> is
26the 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
29and Cb planes have half as many pad bytes after their rows. In other
30words, 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 &times; 4
35pixel 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&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>start&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>start&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>start&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>start&nbsp;+&nbsp;16:</entry>
74 <entry>Cr<subscript>00</subscript></entry>
75 <entry>Cr<subscript>01</subscript></entry>
76 </row>
77 <row>
78 <entry>start&nbsp;+&nbsp;18:</entry>
79 <entry>Cr<subscript>10</subscript></entry>
80 <entry>Cr<subscript>11</subscript></entry>
81 </row>
82 <row>
83 <entry>start&nbsp;+&nbsp;20:</entry>
84 <entry>Cb<subscript>00</subscript></entry>
85 <entry>Cb<subscript>01</subscript></entry>
86 </row>
87 <row>
88 <entry>start&nbsp;+&nbsp;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>
150
151 <!--
152Local Variables:
153mode: sgml
154sgml-parent-document: "pixfmt.sgml"
155indent-tabs-mode: nil
156End:
157 -->
generated by cgit v1.2.2 (git 2.25.0) at 2025-02-01 13:54:13 -0500