[deliverable/linux.git] / Documentation / DocBook / media / v4l / pixfmt-yuv420.xml

    <refentry>
      <refmeta>
	<refentrytitle>V4L2_PIX_FMT_YVU420 ('YV12'), V4L2_PIX_FMT_YUV420 ('YU12')</refentrytitle>
	&manvol;
     </refmeta>
      <refnamediv>
	<refname id="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></refname>
	<refname id="V4L2-PIX-FMT-YUV420"><constant>V4L2_PIX_FMT_YUV420</constant></refname>
	<refpurpose>Planar formats with &frac12; horizontal and
vertical chroma resolution, also known as YUV 4:2:0</refpurpose>
      </refnamediv>
      <refsect1>
	<title>Description</title>

	<para>These are planar formats, as opposed to a packed format.
The three components are separated into three sub- images or planes.
The Y plane is first. The Y plane has one byte per pixel. For
<constant>V4L2_PIX_FMT_YVU420</constant>, the Cr plane immediately
follows the Y plane in memory. The Cr plane is half the width and half
the height of the Y plane (and of the image). Each Cr belongs to four
pixels, a two-by-two square of the image. For example,
Cr<subscript>0</subscript> belongs to Y'<subscript>00</subscript>,
Y'<subscript>01</subscript>, Y'<subscript>10</subscript>, and
Y'<subscript>11</subscript>. Following the Cr plane is the Cb plane,
just like the Cr plane. <constant>V4L2_PIX_FMT_YUV420</constant> is
the same except the Cb plane comes first, then the Cr plane.</para>

	<para>If the Y plane has pad bytes after each row, then the Cr
and Cb planes have half as many pad bytes after their rows. In other
words, two Cx rows (including padding) is exactly as long as one Y row
(including padding).</para>

	<example>
	  <title><constant>V4L2_PIX_FMT_YVU420</constant> 4 &times; 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>start&nbsp;+&nbsp;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>start&nbsp;+&nbsp;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>start&nbsp;+&nbsp;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>start&nbsp;+&nbsp;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>start&nbsp;+&nbsp;16:</entry>
		      <entry>Cr<subscript>00</subscript></entry>
		      <entry>Cr<subscript>01</subscript></entry>
		    </row>
		    <row>
		      <entry>start&nbsp;+&nbsp;18:</entry>
		      <entry>Cr<subscript>10</subscript></entry>
		      <entry>Cr<subscript>11</subscript></entry>
		    </row>
		    <row>
		      <entry>start&nbsp;+&nbsp;20:</entry>
		      <entry>Cb<subscript>00</subscript></entry>
		      <entry>Cb<subscript>01</subscript></entry>
		    </row>
		    <row>
		      <entry>start&nbsp;+&nbsp;22:</entry>
		      <entry>Cb<subscript>10</subscript></entry>
		      <entry>Cb<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>
Commit	Line	Data
8e080c2e MCC	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>