1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
<refentry>
<refmeta>
<refentrytitle>V4L2_PIX_FMT_NV12M ('NM12'), V4L2_PIX_FMT_NV21M ('NM21'), V4L2_PIX_FMT_NV12MT_16X16</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname id="V4L2-PIX-FMT-NV12M"><constant>V4L2_PIX_FMT_NV12M</constant></refname>
<refname id="V4L2-PIX-FMT-NV21M"><constant>V4L2_PIX_FMT_NV21M</constant></refname>
<refname id="V4L2-PIX-FMT-NV12MT-16X16"><constant>V4L2_PIX_FMT_NV12MT_16X16</constant></refname>
<refpurpose>Variation of <constant>V4L2_PIX_FMT_NV12</constant> and <constant>V4L2_PIX_FMT_NV21</constant> with planes
non contiguous in memory. </refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>This is a multi-planar, two-plane version of the YUV 4:2:0 format.
The three components are separated into two sub-images or planes.
<constant>V4L2_PIX_FMT_NV12M</constant> differs from <constant>V4L2_PIX_FMT_NV12
</constant> in that the two planes are non-contiguous in memory, i.e. the chroma
plane do not necessarily immediately follows the luma plane.
The luminance data occupies the first plane. The Y plane has one byte per pixel.
In the second plane there is a chrominance data with alternating chroma samples.
The CbCr plane is the same width, in bytes, as the Y plane (and of the image),
but is half as tall in pixels. Each CbCr pair belongs to four pixels. For example,
Cb<subscript>0</subscript>/Cr<subscript>0</subscript> belongs to
Y'<subscript>00</subscript>, Y'<subscript>01</subscript>,
Y'<subscript>10</subscript>, Y'<subscript>11</subscript>.
<constant>V4L2_PIX_FMT_NV12MT_16X16</constant> is the tiled version of
<constant>V4L2_PIX_FMT_NV12M</constant> with 16x16 macroblock tiles. Here pixels
are arranged in 16x16 2D tiles and tiles are arranged in linear order in memory.
<constant>V4L2_PIX_FMT_NV21M</constant> is the same as <constant>V4L2_PIX_FMT_NV12M</constant>
except the Cb and Cr bytes are swapped, the CrCb plane starts with a Cr byte.</para>
<para><constant>V4L2_PIX_FMT_NV12M</constant> is intended to be
used only in drivers and applications that support the multi-planar API,
described in <xref linkend="planar-apis"/>. </para>
<para>If the Y plane has pad bytes after each row, then the
CbCr plane has as many pad bytes after its rows.</para>
<example>
<title><constant>V4L2_PIX_FMT_NV12M</constant> 4 × 4 pixel image</title>
<formalpara>
<title>Byte Order.</title>
<para>Each cell is one byte.
<informaltable frame="none">
<tgroup cols="5" align="center">
<colspec align="left" colwidth="2*" />
<tbody valign="top">
<row>
<entry>start0 + 0:</entry>
<entry>Y'<subscript>00</subscript></entry>
<entry>Y'<subscript>01</subscript></entry>
<entry>Y'<subscript>02</subscript></entry>
<entry>Y'<subscript>03</subscript></entry>
</row>
<row>
<entry>start0 + 4:</entry>
<entry>Y'<subscript>10</subscript></entry>
<entry>Y'<subscript>11</subscript></entry>
<entry>Y'<subscript>12</subscript></entry>
<entry>Y'<subscript>13</subscript></entry>
</row>
<row>
<entry>start0 + 8:</entry>
<entry>Y'<subscript>20</subscript></entry>
<entry>Y'<subscript>21</subscript></entry>
<entry>Y'<subscript>22</subscript></entry>
<entry>Y'<subscript>23</subscript></entry>
</row>
<row>
<entry>start0 + 12:</entry>
<entry>Y'<subscript>30</subscript></entry>
<entry>Y'<subscript>31</subscript></entry>
<entry>Y'<subscript>32</subscript></entry>
<entry>Y'<subscript>33</subscript></entry>
</row>
<row>
<entry></entry>
</row>
<row>
<entry>start1 + 0:</entry>
<entry>Cb<subscript>00</subscript></entry>
<entry>Cr<subscript>00</subscript></entry>
<entry>Cb<subscript>01</subscript></entry>
<entry>Cr<subscript>01</subscript></entry>
</row>
<row>
<entry>start1 + 4:</entry>
<entry>Cb<subscript>10</subscript></entry>
<entry>Cr<subscript>10</subscript></entry>
<entry>Cb<subscript>11</subscript></entry>
<entry>Cr<subscript>11</subscript></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</formalpara>
<formalpara>
<title>Color Sample Location.</title>
<para>
<informaltable frame="none">
<tgroup cols="7" align="center">
<tbody valign="top">
<row>
<entry></entry>
<entry>0</entry><entry></entry><entry>1</entry><entry></entry>
<entry>2</entry><entry></entry><entry>3</entry>
</row>
<row>
<entry>0</entry>
<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
<entry>Y</entry><entry></entry><entry>Y</entry>
</row>
<row>
<entry></entry>
<entry></entry><entry>C</entry><entry></entry><entry></entry>
<entry></entry><entry>C</entry><entry></entry>
</row>
<row>
<entry>1</entry>
<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
<entry>Y</entry><entry></entry><entry>Y</entry>
</row>
<row>
<entry></entry>
</row>
<row>
<entry>2</entry>
<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
<entry>Y</entry><entry></entry><entry>Y</entry>
</row>
<row>
<entry></entry>
<entry></entry><entry>C</entry><entry></entry><entry></entry>
<entry></entry><entry>C</entry><entry></entry>
</row>
<row>
<entry>3</entry>
<entry>Y</entry><entry></entry><entry>Y</entry><entry></entry>
<entry>Y</entry><entry></entry><entry>Y</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</formalpara>
</example>
</refsect1>
</refentry>
|
