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authorMauro Carvalho Chehab <mchehab@redhat.com>2011-05-31 15:27:44 -0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-07-27 16:52:05 -0400
commit4266129964b8238526936d723de65b419d8069c6 (patch)
tree38c6b5cd3dc99b8599391ffad3b87e399bef56a2 /Documentation/DocBook/media/v4l/pixfmt-yuv420.xml
parent04893043ae9ea8aa82b712491ed25ba6c4ffbca3 (diff)
[media] DocBook: Move all media docbook stuff into its own directory
This patch addresses several issues pointed by Randy Dunlap <rdunlap@xenotime.net> at changeset ece722c: - In the generated index.html file, "media" is listed first, but it should be listed in alphabetical order, not first. - The generated files are (hidden) in .tmpmedia/ - The link from the top-level index.html file to "media" is to media/index.html, but the file is actually in .tmpmedia/media/index.html - Please build docs with and without using "O=builddir" and test that. - Would it be possible for media to have its own Makefile instead of merging into this one? Due to the way cleandocs target works, I had to rename the media DocBook to media_api, otherwise cleandocs would remove the /media directory. Thanks-to: Randy Dunlap <rdunlap@xenotime.net> 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 2025-02-19 13:39:15 -0500