About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / DocBook / media / v4l / pixfmt.xml




Custom Search

Based on kernel version 4.0. Page generated on 2015-04-14 21:23 EST.

1	  <title>Image Formats</title>
2	
3	  <para>The V4L2 API was primarily designed for devices exchanging
4	image data with applications. The
5	<structname>v4l2_pix_format</structname> and <structname>v4l2_pix_format_mplane
6	</structname> structures define the format and layout of an image in memory.
7	The former is used with the single-planar API, while the latter is used with the
8	multi-planar version (see <xref linkend="planar-apis"/>). Image formats are
9	negotiated with the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video
10	capturing and output, for overlay frame buffer formats see also
11	&VIDIOC-G-FBUF;.)</para>
12	
13	<section>
14	  <title>Single-planar format structure</title>
15	  <table pgwide="1" frame="none" id="v4l2-pix-format">
16	    <title>struct <structname>v4l2_pix_format</structname></title>
17	    <tgroup cols="3">
18	      &cs-str;
19	      <tbody valign="top">
20		<row>
21		  <entry>__u32</entry>
22		  <entry><structfield>width</structfield></entry>
23		  <entry>Image width in pixels.</entry>
24		</row>
25		<row>
26		  <entry>__u32</entry>
27		  <entry><structfield>height</structfield></entry>
28		  <entry>Image height in pixels. If <structfield>field</structfield> is
29		  one of <constant>V4L2_FIELD_TOP</constant>, <constant>V4L2_FIELD_BOTTOM</constant>
30		  or <constant>V4L2_FIELD_ALTERNATE</constant> then height refers to the
31		  number of lines in the field, otherwise it refers to the number of
32		  lines in the frame (which is twice the field height for interlaced
33		  formats).</entry>
34		</row>
35		<row>
36		  <entry spanname="hspan">Applications set these fields to
37	request an image size, drivers return the closest possible values. In
38	case of planar formats the <structfield>width</structfield> and
39	<structfield>height</structfield> applies to the largest plane. To
40	avoid ambiguities drivers must return values rounded up to a multiple
41	of the scale factor of any smaller planes. For example when the image
42	format is YUV 4:2:0, <structfield>width</structfield> and
43	<structfield>height</structfield> must be multiples of two.</entry>
44		</row>
45		<row>
46		  <entry>__u32</entry>
47		  <entry><structfield>pixelformat</structfield></entry>
48		  <entry>The pixel format or type of compression, set by the
49	application. This is a little endian <link
50	linkend="v4l2-fourcc">four character code</link>. V4L2 defines
51	standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
52	linkend="yuv-formats" />, and reserved codes in <xref
53	linkend="reserved-formats" /></entry>
54		</row>
55		<row>
56		  <entry>&v4l2-field;</entry>
57		  <entry><structfield>field</structfield></entry>
58		  <entry>Video images are typically interlaced. Applications
59	can request to capture or output only the top or bottom field, or both
60	fields interlaced or sequentially stored in one buffer or alternating
61	in separate buffers. Drivers return the actual field order selected.
62	For more details on fields see <xref linkend="field-order" />.</entry>
63		</row>
64		<row>
65		  <entry>__u32</entry>
66		  <entry><structfield>bytesperline</structfield></entry>
67		  <entry>Distance in bytes between the leftmost pixels in two
68	adjacent lines.</entry>
69		</row>
70		<row>
71		  <entry spanname="hspan"><para>Both applications and drivers
72	can set this field to request padding bytes at the end of each line.
73	Drivers however may ignore the value requested by the application,
74	returning <structfield>width</structfield> times bytes per pixel or a
75	larger value required by the hardware. That implies applications can
76	just set this field to zero to get a reasonable
77	default.</para><para>Video hardware may access padding bytes,
78	therefore they must reside in accessible memory. Consider cases where
79	padding bytes after the last line of an image cross a system page
80	boundary. Input devices may write padding bytes, the value is
81	undefined. Output devices ignore the contents of padding
82	bytes.</para><para>When the image format is planar the
83	<structfield>bytesperline</structfield> value applies to the largest
84	plane and is divided by the same factor as the
85	<structfield>width</structfield> field for any smaller planes. For
86	example the Cb and Cr planes of a YUV 4:2:0 image have half as many
87	padding bytes following each line as the Y plane. To avoid ambiguities
88	drivers must return a <structfield>bytesperline</structfield> value
89	rounded up to a multiple of the scale factor.</para>
90	<para>For compressed formats the <structfield>bytesperline</structfield>
91	value makes no sense. Applications and drivers must set this to 0 in
92	that case.</para></entry>
93		</row>
94		<row>
95		  <entry>__u32</entry>
96		  <entry><structfield>sizeimage</structfield></entry>
97		  <entry>Size in bytes of the buffer to hold a complete image,
98	set by the driver. Usually this is
99	<structfield>bytesperline</structfield> times
100	<structfield>height</structfield>. When the image consists of variable
101	length compressed data this is the maximum number of bytes required to
102	hold an image.</entry>
103		</row>
104		<row>
105		  <entry>&v4l2-colorspace;</entry>
106		  <entry><structfield>colorspace</structfield></entry>
107		  <entry>This information supplements the
108	<structfield>pixelformat</structfield> and must be set by the driver for
109	capture streams and by the application for output streams,
110	see <xref linkend="colorspaces" />.</entry>
111		</row>
112		<row>
113		  <entry>__u32</entry>
114		  <entry><structfield>priv</structfield></entry>
115		  <entry><para>This field indicates whether the remaining fields of the
116	<structname>v4l2_pix_format</structname> structure, also called the extended
117	fields, are valid. When set to <constant>V4L2_PIX_FMT_PRIV_MAGIC</constant>, it
118	indicates that the extended fields have been correctly initialized. When set to
119	any other value it indicates that the extended fields contain undefined values.
120	</para>
121	<para>Applications that wish to use the pixel format extended fields must first
122	ensure that the feature is supported by querying the device for the
123	<link linkend="querycap"><constant>V4L2_CAP_EXT_PIX_FORMAT</constant></link>
124	capability. If the capability isn't set the pixel format extended fields are not
125	supported and using the extended fields will lead to undefined results.</para>
126	<para>To use the extended fields, applications must set the
127	<structfield>priv</structfield> field to
128	<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant>, initialize all the extended fields
129	and zero the unused bytes of the <structname>v4l2_format</structname>
130	<structfield>raw_data</structfield> field.</para>
131	<para>When the <structfield>priv</structfield> field isn't set to
132	<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> drivers must act as if all the
133	extended fields were set to zero. On return drivers must set the
134	<structfield>priv</structfield> field to
135	<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> and all the extended fields to
136	applicable values.</para></entry>
137		</row>
138		<row>
139		  <entry>__u32</entry>
140		  <entry><structfield>flags</structfield></entry>
141		  <entry>Flags set by the application or driver, see <xref
142	linkend="format-flags" />.</entry>
143		</row>
144		<row>
145		  <entry>&v4l2-ycbcr-encoding;</entry>
146		  <entry><structfield>ycbcr_enc</structfield></entry>
147		  <entry>This information supplements the
148	<structfield>colorspace</structfield> and must be set by the driver for
149	capture streams and by the application for output streams,
150	see <xref linkend="colorspaces" />.</entry>
151		</row>
152		<row>
153		  <entry>&v4l2-quantization;</entry>
154		  <entry><structfield>quantization</structfield></entry>
155		  <entry>This information supplements the
156	<structfield>colorspace</structfield> and must be set by the driver for
157	capture streams and by the application for output streams,
158	see <xref linkend="colorspaces" />.</entry>
159		</row>
160	      </tbody>
161	    </tgroup>
162	  </table>
163	</section>
164	
165	<section>
166	  <title>Multi-planar format structures</title>
167	  <para>The <structname>v4l2_plane_pix_format</structname> structures define
168	    size and layout for each of the planes in a multi-planar format.
169	    The <structname>v4l2_pix_format_mplane</structname> structure contains
170	    information common to all planes (such as image width and height) and
171	    an array of <structname>v4l2_plane_pix_format</structname> structures,
172	    describing all planes of that format.</para>
173	  <table pgwide="1" frame="none" id="v4l2-plane-pix-format">
174	    <title>struct <structname>v4l2_plane_pix_format</structname></title>
175	    <tgroup cols="3">
176	      &cs-str;
177	      <tbody valign="top">
178	        <row>
179	          <entry>__u32</entry>
180	          <entry><structfield>sizeimage</structfield></entry>
181	          <entry>Maximum size in bytes required for image data in this plane.
182	          </entry>
183	        </row>
184	        <row>
185	          <entry>__u16</entry>
186	          <entry><structfield>bytesperline</structfield></entry>
187	          <entry>Distance in bytes between the leftmost pixels in two adjacent
188	            lines. See &v4l2-pix-format;.</entry>
189	        </row>
190	        <row>
191	          <entry>__u16</entry>
192	          <entry><structfield>reserved[7]</structfield></entry>
193	          <entry>Reserved for future extensions. Should be zeroed by the
194	           application.</entry>
195	        </row>
196	      </tbody>
197	    </tgroup>
198	  </table>
199	  <table pgwide="1" frame="none" id="v4l2-pix-format-mplane">
200	    <title>struct <structname>v4l2_pix_format_mplane</structname></title>
201	    <tgroup cols="3">
202	      &cs-str;
203	      <tbody valign="top">
204	        <row>
205	          <entry>__u32</entry>
206	          <entry><structfield>width</structfield></entry>
207	          <entry>Image width in pixels. See &v4l2-pix-format;.</entry>
208	        </row>
209	        <row>
210	          <entry>__u32</entry>
211	          <entry><structfield>height</structfield></entry>
212	          <entry>Image height in pixels. See &v4l2-pix-format;.</entry>
213	        </row>
214	        <row>
215	          <entry>__u32</entry>
216	          <entry><structfield>pixelformat</structfield></entry>
217	          <entry>The pixel format. Both single- and multi-planar four character
218	codes can be used.</entry>
219	        </row>
220	        <row>
221	          <entry>&v4l2-field;</entry>
222	          <entry><structfield>field</structfield></entry>
223	          <entry>See &v4l2-pix-format;.</entry>
224	        </row>
225	        <row>
226	          <entry>&v4l2-colorspace;</entry>
227	          <entry><structfield>colorspace</structfield></entry>
228	          <entry>See &v4l2-pix-format;.</entry>
229	        </row>
230	        <row>
231	          <entry>&v4l2-plane-pix-format;</entry>
232	          <entry><structfield>plane_fmt[VIDEO_MAX_PLANES]</structfield></entry>
233	          <entry>An array of structures describing format of each plane this
234	          pixel format consists of. The number of valid entries in this array
235	          has to be put in the <structfield>num_planes</structfield>
236	          field.</entry>
237	        </row>
238	        <row>
239	          <entry>__u8</entry>
240	          <entry><structfield>num_planes</structfield></entry>
241	          <entry>Number of planes (i.e. separate memory buffers) for this format
242	          and the number of valid entries in the
243	          <structfield>plane_fmt</structfield> array.</entry>
244	        </row>
245		<row>
246		  <entry>__u8</entry>
247		  <entry><structfield>flags</structfield></entry>
248		  <entry>Flags set by the application or driver, see <xref
249	linkend="format-flags" />.</entry>
250		</row>
251		<row>
252		  <entry>&v4l2-ycbcr-encoding;</entry>
253		  <entry><structfield>ycbcr_enc</structfield></entry>
254		  <entry>This information supplements the
255	<structfield>colorspace</structfield> and must be set by the driver for
256	capture streams and by the application for output streams,
257	see <xref linkend="colorspaces" />.</entry>
258		</row>
259		<row>
260		  <entry>&v4l2-quantization;</entry>
261		  <entry><structfield>quantization</structfield></entry>
262		  <entry>This information supplements the
263	<structfield>colorspace</structfield> and must be set by the driver for
264	capture streams and by the application for output streams,
265	see <xref linkend="colorspaces" />.</entry>
266		</row>
267	        <row>
268	          <entry>__u8</entry>
269	          <entry><structfield>reserved[8]</structfield></entry>
270	          <entry>Reserved for future extensions. Should be zeroed by the
271	           application.</entry>
272	        </row>
273	      </tbody>
274	    </tgroup>
275	  </table>
276	</section>
277	
278	  <section>
279	    <title>Standard Image Formats</title>
280	
281	    <para>In order to exchange images between drivers and
282	applications, it is necessary to have standard image data formats
283	which both sides will interpret the same way. V4L2 includes several
284	such formats, and this section is intended to be an unambiguous
285	specification of the standard image data formats in V4L2.</para>
286	
287	    <para>V4L2 drivers are not limited to these formats, however.
288	Driver-specific formats are possible. In that case the application may
289	depend on a codec to convert images to one of the standard formats
290	when needed. But the data can still be stored and retrieved in the
291	proprietary format. For example, a device may support a proprietary
292	compressed format. Applications can still capture and save the data in
293	the compressed format, saving much disk space, and later use a codec
294	to convert the images to the X Windows screen format when the video is
295	to be displayed.</para>
296	
297	    <para>Even so, ultimately, some standard formats are needed, so
298	the V4L2 specification would not be complete without well-defined
299	standard formats.</para>
300	
301	    <para>The V4L2 standard formats are mainly uncompressed formats. The
302	pixels are always arranged in memory from left to right, and from top
303	to bottom. The first byte of data in the image buffer is always for
304	the leftmost pixel of the topmost row. Following that is the pixel
305	immediately to its right, and so on until the end of the top row of
306	pixels. Following the rightmost pixel of the row there may be zero or
307	more bytes of padding to guarantee that each row of pixel data has a
308	certain alignment. Following the pad bytes, if any, is data for the
309	leftmost pixel of the second row from the top, and so on. The last row
310	has just as many pad bytes after it as the other rows.</para>
311	
312	    <para>In V4L2 each format has an identifier which looks like
313	<constant>PIX_FMT_XXX</constant>, defined in the <link
314	linkend="videodev">videodev2.h</link> header file. These identifiers
315	represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link>
316	which are also listed below, however they are not the same as those
317	used in the Windows world.</para>
318	
319	    <para>For some formats, data is stored in separate, discontiguous
320	memory buffers. Those formats are identified by a separate set of FourCC codes
321	and are referred to as "multi-planar formats". For example, a YUV422 frame is
322	normally stored in one memory buffer, but it can also be placed in two or three
323	separate buffers, with Y component in one buffer and CbCr components in another
324	in the 2-planar version or with each component in its own buffer in the
325	3-planar case. Those sub-buffers are referred to as "planes".</para>
326	  </section>
327	
328	  <section id="colorspaces">
329	    <title>Colorspaces</title>
330	
331	    <para>'Color' is a very complex concept and depends on physics, chemistry and
332	biology. Just because you have three numbers that describe the 'red', 'green'
333	and 'blue' components of the color of a pixel does not mean that you can accurately
334	display that color. A colorspace defines what it actually <emphasis>means</emphasis>
335	to have an RGB value of e.g. (255,&nbsp;0,&nbsp;0). That is, which color should be
336	reproduced on the screen in a perfectly calibrated environment.</para>
337	
338	    <para>In order to do that we first need to have a good definition of
339	color, i.e. some way to uniquely and unambiguously define a color so that someone
340	else can reproduce it. Human color vision is trichromatic since the human eye has
341	color receptors that are sensitive to three different wavelengths of light. Hence
342	the need to use three numbers to describe color. Be glad you are not a mantis shrimp
343	as those are sensitive to 12 different wavelengths, so instead of RGB we would be
344	using the ABCDEFGHIJKL colorspace...</para>
345	
346	    <para>Color exists only in the eye and brain and is the result of how strongly
347	color receptors are stimulated. This is based on the Spectral
348	Power Distribution (SPD) which is a graph showing the intensity (radiant power)
349	of the light at wavelengths covering the visible spectrum as it enters the eye.
350	The science of colorimetry is about the relationship between the SPD and color as
351	perceived by the human brain.</para>
352	
353	    <para>Since the human eye has only three color receptors it is perfectly
354	possible that different SPDs will result in the same stimulation of those receptors
355	and are perceived as the same color, even though the SPD of the light is
356	different.</para>
357	
358	   <para>In the 1920s experiments were devised to determine the relationship
359	between SPDs and the perceived color and that resulted in the CIE 1931 standard
360	that defines spectral weighting functions that model the perception of color.
361	Specifically that standard defines functions that can take an SPD and calculate
362	the stimulus for each color receptor. After some further mathematical transforms
363	these stimuli are known as the <emphasis>CIE XYZ tristimulus</emphasis> values
364	and these X, Y and Z values describe a color as perceived by a human unambiguously.
365	These X, Y and Z values are all in the range [0&hellip;1].</para>
366	
367	   <para>The Y value in the CIE XYZ colorspace corresponds to luminance. Often
368	the CIE XYZ colorspace is transformed to the normalized CIE xyY colorspace:</para>
369	
370	   <para>x = X / (X + Y + Z)</para>
371	   <para>y = Y / (X + Y + Z)</para>
372	
373	   <para>The x and y values are the chromaticity coordinates and can be used to
374	define a color without the luminance component Y. It is very confusing to
375	have such similar names for these colorspaces. Just be aware that if colors
376	are specified with lower case 'x' and 'y', then the CIE xyY colorspace is
377	used. Upper case 'X' and 'Y' refer to the CIE XYZ colorspace. Also, y has nothing
378	to do with luminance. Together x and y specify a color, and Y the luminance.
379	That is really all you need to remember from a practical point of view. At
380	the end of this section you will find reading resources that go into much more
381	detail if you are interested.
382	</para>
383	
384	   <para>A monitor or TV will reproduce colors by emitting light at three
385	different wavelengths, the combination of which will stimulate the color receptors
386	in the eye and thus cause the perception of color. Historically these wavelengths
387	were defined by the red, green and blue phosphors used in the displays. These
388	<emphasis>color primaries</emphasis> are part of what defines a colorspace.</para>
389	
390	    <para>Different display devices will have different primaries and some
391	primaries are more suitable for some display technologies than others. This has
392	resulted in a variety of colorspaces that are used for different display
393	technologies or uses. To define a colorspace you need to define the three
394	color primaries (these are typically defined as x,&nbsp;y chromaticity coordinates
395	from the CIE xyY colorspace) but also the white reference: that is the color obtained
396	when all three primaries are at maximum power. This determines the relative power
397	or energy of the primaries. This is usually chosen to be close to daylight which has
398	been defined as the CIE D65 Illuminant.</para>
399	
400	    <para>To recapitulate: the CIE XYZ colorspace uniquely identifies colors.
401	Other colorspaces are defined by three chromaticity coordinates defined in the
402	CIE xyY colorspace. Based on those a 3x3 matrix can be constructed that
403	transforms CIE XYZ colors to colors in the new colorspace.
404	</para>
405	
406	    <para>Both the CIE XYZ and the RGB colorspace that are derived from the
407	specific chromaticity primaries are linear colorspaces. But neither the eye,
408	nor display technology is linear. Doubling the values of all components in
409	the linear colorspace will not be perceived as twice the intensity of the color.
410	So each colorspace also defines a transfer function that takes a linear color
411	component value and transforms it to the non-linear component value, which is a
412	closer match to the non-linear performance of both the eye and displays. Linear
413	component values are denoted RGB, non-linear are denoted as R'G'B'. In general
414	colors used in graphics are all R'G'B', except in openGL which uses linear RGB.
415	Special care should be taken when dealing with openGL to provide linear RGB colors
416	or to use the built-in openGL support to apply the inverse transfer function.</para>
417	
418	    <para>The final piece that defines a colorspace is a function that
419	transforms non-linear R'G'B' to non-linear Y'CbCr. This function is determined
420	by the so-called luma coefficients. There may be multiple possible Y'CbCr
421	encodings allowed for the same colorspace. Many encodings of color
422	prefer to use luma (Y') and chroma (CbCr) instead of R'G'B'. Since the human
423	eye is more sensitive to differences in luminance than in color this encoding
424	allows one to reduce the amount of color information compared to the luma
425	data. Note that the luma (Y') is unrelated to the Y in the CIE XYZ colorspace.
426	Also note that Y'CbCr is often called YCbCr or YUV even though these are
427	strictly speaking wrong.</para>
428	
429	    <para>Sometimes people confuse Y'CbCr as being a colorspace. This is not
430	correct, it is just an encoding of an R'G'B' color into luma and chroma
431	values. The underlying colorspace that is associated with the R'G'B' color
432	is also associated with the Y'CbCr color.</para>
433	
434	    <para>The final step is how the RGB, R'G'B' or Y'CbCr values are
435	quantized. The CIE XYZ colorspace where X, Y and Z are in the range
436	[0&hellip;1] describes all colors that humans can perceive, but the transform to
437	another colorspace will produce colors that are outside the [0&hellip;1] range.
438	Once clamped to the [0&hellip;1] range those colors can no longer be reproduced
439	in that colorspace. This clamping is what reduces the extent or gamut of the
440	colorspace. How the range of [0&hellip;1] is translated to integer values in the
441	range of [0&hellip;255] (or higher, depending on the color depth) is called the
442	quantization. This is <emphasis>not</emphasis> part of the colorspace
443	definition. In practice RGB or R'G'B' values are full range, i.e. they
444	use the full [0&hellip;255] range. Y'CbCr values on the other hand are limited
445	range with Y' using [16&hellip;235] and Cb and Cr using [16&hellip;240].</para>
446	
447	    <para>Unfortunately, in some cases limited range RGB is also used
448	where the components use the range [16&hellip;235]. And full range Y'CbCr also exists
449	using the [0&hellip;255] range.</para>
450	
451	    <para>In order to correctly interpret a color you need to know the
452	quantization range, whether it is R'G'B' or Y'CbCr, the used Y'CbCr encoding
453	and the colorspace.
454	From that information you can calculate the corresponding CIE XYZ color
455	and map that again to whatever colorspace your display device uses.</para>
456	
457	    <para>The colorspace definition itself consists of the three
458	chromaticity primaries, the white reference chromaticity, a transfer
459	function and the luma coefficients needed to transform R'G'B' to Y'CbCr. While
460	some colorspace standards correctly define all four, quite often the colorspace
461	standard only defines some, and you have to rely on other standards for
462	the missing pieces. The fact that colorspaces are often a mix of different
463	standards also led to very confusing naming conventions where the name of
464	a standard was used to name a colorspace when in fact that standard was
465	part of various other colorspaces as well.</para>
466	
467	    <para>If you want to read more about colors and colorspaces, then the
468	following resources are useful: <xref linkend="poynton" /> is a good practical
469	book for video engineers, <xref linkend="colimg" /> has a much broader scope and
470	describes many more aspects of color (physics, chemistry, biology, etc.).
471	The <ulink url="http://www.brucelindbloom.com">http://www.brucelindbloom.com</ulink>
472	website is an excellent resource, especially with respect to the mathematics behind
473	colorspace conversions. The wikipedia <ulink url="http://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_xy_chromaticity_diagram_and_the_CIE_xyY_color_space">CIE 1931 colorspace</ulink> article
474	is also very useful.</para>
475	  </section>
476	
477	  <section>
478	    <title>Defining Colorspaces in V4L2</title>
479	    <para>In V4L2 colorspaces are defined by three values. The first is the colorspace
480	identifier (&v4l2-colorspace;) which defines the chromaticities, the transfer
481	function, the default Y'CbCr encoding and the default quantization method. The second
482	is the Y'CbCr encoding identifier (&v4l2-ycbcr-encoding;) to specify non-standard
483	Y'CbCr encodings and the third is the quantization identifier (&v4l2-quantization;)
484	to specify non-standard quantization methods. Most of the time only the colorspace
485	field of &v4l2-pix-format; or &v4l2-pix-format-mplane; needs to be filled in. Note
486	that the default R'G'B' quantization is always full range for all colorspaces,
487	so this won't be mentioned explicitly for each colorspace description.</para>
488	
489	    <table pgwide="1" frame="none" id="v4l2-colorspace">
490	      <title>V4L2 Colorspaces</title>
491	      <tgroup cols="2" align="left">
492		&cs-def;
493		<thead>
494		  <row>
495		    <entry>Identifier</entry>
496		    <entry>Details</entry>
497		  </row>
498		</thead>
499		<tbody valign="top">
500		  <row>
501		    <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry>
502		    <entry>See <xref linkend="col-smpte-170m" />.</entry>
503		  </row>
504		  <row>
505		    <entry><constant>V4L2_COLORSPACE_REC709</constant></entry>
506		    <entry>See <xref linkend="col-rec709" />.</entry>
507		  </row>
508		  <row>
509		    <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry>
510		    <entry>See <xref linkend="col-srgb" />.</entry>
511		  </row>
512		  <row>
513		    <entry><constant>V4L2_COLORSPACE_ADOBERGB</constant></entry>
514		    <entry>See <xref linkend="col-adobergb" />.</entry>
515		  </row>
516		  <row>
517		    <entry><constant>V4L2_COLORSPACE_BT2020</constant></entry>
518		    <entry>See <xref linkend="col-bt2020" />.</entry>
519		  </row>
520		  <row>
521		    <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry>
522		    <entry>See <xref linkend="col-smpte-240m" />.</entry>
523		  </row>
524		  <row>
525		    <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry>
526		    <entry>See <xref linkend="col-sysm" />.</entry>
527		  </row>
528		  <row>
529		    <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry>
530		    <entry>See <xref linkend="col-sysbg" />.</entry>
531		  </row>
532		  <row>
533		    <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry>
534		    <entry>See <xref linkend="col-jpeg" />.</entry>
535		  </row>
536		</tbody>
537	      </tgroup>
538	    </table>
539	
540	    <table pgwide="1" frame="none" id="v4l2-ycbcr-encoding">
541	      <title>V4L2 Y'CbCr Encodings</title>
542	      <tgroup cols="2" align="left">
543		&cs-def;
544		<thead>
545		  <row>
546		    <entry>Identifier</entry>
547		    <entry>Details</entry>
548		  </row>
549		</thead>
550		<tbody valign="top">
551		  <row>
552		    <entry><constant>V4L2_YCBCR_ENC_DEFAULT</constant></entry>
553		    <entry>Use the default Y'CbCr encoding as defined by the colorspace.</entry>
554		  </row>
555		  <row>
556		    <entry><constant>V4L2_YCBCR_ENC_601</constant></entry>
557		    <entry>Use the BT.601 Y'CbCr encoding.</entry>
558		  </row>
559		  <row>
560		    <entry><constant>V4L2_YCBCR_ENC_709</constant></entry>
561		    <entry>Use the Rec. 709 Y'CbCr encoding.</entry>
562		  </row>
563		  <row>
564		    <entry><constant>V4L2_YCBCR_ENC_XV601</constant></entry>
565		    <entry>Use the extended gamut xvYCC BT.601 encoding.</entry>
566		  </row>
567		  <row>
568		    <entry><constant>V4L2_YCBCR_ENC_XV709</constant></entry>
569		    <entry>Use the extended gamut xvYCC Rec. 709 encoding.</entry>
570		  </row>
571		  <row>
572		    <entry><constant>V4L2_YCBCR_ENC_SYCC</constant></entry>
573		    <entry>Use the extended gamut sYCC encoding.</entry>
574		  </row>
575		  <row>
576		    <entry><constant>V4L2_YCBCR_ENC_BT2020</constant></entry>
577		    <entry>Use the default non-constant luminance BT.2020 Y'CbCr encoding.</entry>
578		  </row>
579		  <row>
580		    <entry><constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant></entry>
581		    <entry>Use the constant luminance BT.2020 Yc'CbcCrc encoding.</entry>
582		  </row>
583		</tbody>
584	      </tgroup>
585	    </table>
586	
587	    <table pgwide="1" frame="none" id="v4l2-quantization">
588	      <title>V4L2 Quantization Methods</title>
589	      <tgroup cols="2" align="left">
590		&cs-def;
591		<thead>
592		  <row>
593		    <entry>Identifier</entry>
594		    <entry>Details</entry>
595		  </row>
596		</thead>
597		<tbody valign="top">
598		  <row>
599		    <entry><constant>V4L2_QUANTIZATION_DEFAULT</constant></entry>
600		    <entry>Use the default quantization encoding as defined by the colorspace.
601	This is always full range for R'G'B' and usually limited range for Y'CbCr.</entry>
602		  </row>
603		  <row>
604		    <entry><constant>V4L2_QUANTIZATION_FULL_RANGE</constant></entry>
605		    <entry>Use the full range quantization encoding. I.e. the range [0&hellip;1]
606	is mapped to [0&hellip;255] (with possible clipping to [1&hellip;254] to avoid the
607	0x00 and 0xff values). Cb and Cr are mapped from [-0.5&hellip;0.5] to [0&hellip;255]
608	(with possible clipping to [1&hellip;254] to avoid the 0x00 and 0xff values).</entry>
609		  </row>
610		  <row>
611		    <entry><constant>V4L2_QUANTIZATION_LIM_RANGE</constant></entry>
612		    <entry>Use the limited range quantization encoding. I.e. the range [0&hellip;1]
613	is mapped to [16&hellip;235]. Cb and Cr are mapped from [-0.5&hellip;0.5] to [16&hellip;240].
614	</entry>
615		  </row>
616		</tbody>
617	      </tgroup>
618	    </table>
619	  </section>
620	
621	  <section>
622	    <title>Detailed Colorspace Descriptions</title>
623	    <section>
624	      <title id="col-smpte-170m">Colorspace SMPTE 170M (<constant>V4L2_COLORSPACE_SMPTE170M</constant>)</title>
625	      <para>The <xref linkend="smpte170m" /> standard defines the colorspace used by NTSC and PAL and by SDTV
626	in general. The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>.
627	The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and
628	the white reference are:</para>
629	      <table frame="none">
630	        <title>SMPTE 170M Chromaticities</title>
631	        <tgroup cols="3" align="left">
632	          &cs-str;
633	    	<thead>
634	    	  <row>
635	    	    <entry>Color</entry>
636	    	    <entry>x</entry>
637	    	    <entry>y</entry>
638	    	  </row>
639	    	</thead>
640	          <tbody valign="top">
641	            <row>
642	              <entry>Red</entry>
643	              <entry>0.630</entry>
644	              <entry>0.340</entry>
645	            </row>
646	            <row>
647	              <entry>Green</entry>
648	              <entry>0.310</entry>
649	              <entry>0.595</entry>
650	            </row>
651	            <row>
652	              <entry>Blue</entry>
653	              <entry>0.155</entry>
654	              <entry>0.070</entry>
655	            </row>
656	            <row>
657	              <entry>White Reference (D65)</entry>
658	              <entry>0.3127</entry>
659	              <entry>0.3290</entry>
660	            </row>
661	          </tbody>
662	        </tgroup>
663	      </table>
664	      <para>The red, green and blue chromaticities are also often referred to
665	as the SMPTE C set, so this colorspace is sometimes called SMPTE C as well.</para>
666	      <variablelist>
667		<varlistentry>
668	          <term>The transfer function defined for SMPTE 170M is the same as the
669	one defined in Rec. 709. Normally L is in the range [0&hellip;1], but for the extended
670	gamut xvYCC encoding values outside that range are allowed.</term>
671		  <listitem>
672	            <para>L' = -1.099(-L)<superscript>0.45</superscript>&nbsp;+&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&le;&nbsp;-0.018</para>
673	            <para>L' = 4.5L&nbsp;for&nbsp;-0.018&nbsp;&lt;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
674	            <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&ge;&nbsp;0.018</para>
675		  </listitem>
676		</varlistentry>
677	      </variablelist>
678	      <variablelist>
679		<varlistentry>
680	          <term>Inverse Transfer function:</term>
681		  <listitem>
682	            <para>L = -((L'&nbsp;-&nbsp;0.099)&nbsp;/&nbsp;-1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&le;&nbsp;-0.081</para>
683	            <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;-0.081&nbsp;&lt;&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
684	            <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
685		  </listitem>
686		</varlistentry>
687	      </variablelist>
688	      <variablelist>
689		<varlistentry>
690	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with
691	the following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
692		  <listitem>
693	            <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
694	            <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
695	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
696		  </listitem>
697		</varlistentry>
698	      </variablelist>
699	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
700	clamped to the range [-0.5&hellip;0.5]. This conversion to Y'CbCr is identical to the one
701	defined in the <xref linkend="itu601" /> standard and this colorspace is sometimes called BT.601 as well, even
702	though BT.601 does not mention any color primaries.</para>
703	      <para>The default quantization is limited range, but full range is possible although
704	rarely seen.</para>
705	      <para>The <constant>V4L2_YCBCR_ENC_601</constant> encoding as described above is the
706	default for this colorspace, but it can be overridden with <constant>V4L2_YCBCR_ENC_709</constant>,
707	in which case the Rec. 709 Y'CbCr encoding is used.</para>
708	      <variablelist>
709		<varlistentry>
710	      	  <term>The xvYCC 601 encoding (<constant>V4L2_YCBCR_ENC_XV601</constant>, <xref linkend="xvycc" />) is similar
711	to the BT.601 encoding, but it allows for R', G' and B' values that are outside the range
712	[0&hellip;1]. The resulting Y', Cb and Cr values are scaled and offset:</term>
713		  <listitem>
714	            <para>Y'&nbsp;=&nbsp;(219&nbsp;/&nbsp;255)&nbsp;*&nbsp;(0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B')&nbsp;+&nbsp;(16&nbsp;/&nbsp;255)</para>
715	            <para>Cb&nbsp;=&nbsp;(224&nbsp;/&nbsp;255)&nbsp;*&nbsp;(-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B')</para>
716	            <para>Cr&nbsp;=&nbsp;(224&nbsp;/&nbsp;255)&nbsp;*&nbsp;(0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B')</para>
717		  </listitem>
718		</varlistentry>
719	      </variablelist>
720	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are clamped
721	to the range [-0.5&hellip;0.5]. The non-standard xvYCC 709 encoding can also be used by selecting
722	<constant>V4L2_YCBCR_ENC_XV709</constant>. The xvYCC encodings always use full range
723	quantization.</para>
724	    </section>
725	
726	    <section>
727	      <title id="col-rec709">Colorspace Rec. 709 (<constant>V4L2_COLORSPACE_REC709</constant>)</title>
728	      <para>The <xref linkend="itu709" /> standard defines the colorspace used by HDTV in general. The default
729	Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_709</constant>. The default Y'CbCr quantization is
730	limited range. The chromaticities of the primary colors and the white reference are:</para>
731	      <table frame="none">
732	        <title>Rec. 709 Chromaticities</title>
733	        <tgroup cols="3" align="left">
734	          &cs-str;
735	    	<thead>
736	    	  <row>
737	    	    <entry>Color</entry>
738	    	    <entry>x</entry>
739	    	    <entry>y</entry>
740	    	  </row>
741	    	</thead>
742	          <tbody valign="top">
743	            <row>
744	              <entry>Red</entry>
745	              <entry>0.640</entry>
746	              <entry>0.330</entry>
747	            </row>
748	            <row>
749	              <entry>Green</entry>
750	              <entry>0.300</entry>
751	              <entry>0.600</entry>
752	            </row>
753	            <row>
754	              <entry>Blue</entry>
755	              <entry>0.150</entry>
756	              <entry>0.060</entry>
757	            </row>
758	            <row>
759	              <entry>White Reference (D65)</entry>
760	              <entry>0.3127</entry>
761	              <entry>0.3290</entry>
762	            </row>
763	          </tbody>
764	        </tgroup>
765	      </table>
766	      <para>The full name of this standard is Rec. ITU-R BT.709-5.</para>
767	      <variablelist>
768		<varlistentry>
769	          <term>Transfer function. Normally L is in the range [0&hellip;1], but for the extended
770	gamut xvYCC encoding values outside that range are allowed.</term>
771		  <listitem>
772	            <para>L' = -1.099(-L)<superscript>0.45</superscript>&nbsp;+&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&le;&nbsp;-0.018</para>
773	            <para>L' = 4.5L&nbsp;for&nbsp;-0.018&nbsp;&lt;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
774	            <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&ge;&nbsp;0.018</para>
775		  </listitem>
776		</varlistentry>
777	      </variablelist>
778	      <variablelist>
779		<varlistentry>
780	          <term>Inverse Transfer function:</term>
781		  <listitem>
782	            <para>L = -((L'&nbsp;-&nbsp;0.099)&nbsp;/&nbsp;-1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&le;&nbsp;-0.081</para>
783	            <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;-0.081&nbsp;&lt;&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
784	            <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
785		  </listitem>
786		</varlistentry>
787	      </variablelist>
788	      <variablelist>
789		<varlistentry>
790	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following
791	<constant>V4L2_YCBCR_ENC_709</constant> encoding:</term>
792		  <listitem>
793	            <para>Y'&nbsp;=&nbsp;0.2126R'&nbsp;+&nbsp;0.7152G'&nbsp;+&nbsp;0.0722B'</para>
794	            <para>Cb&nbsp;=&nbsp;-0.1146R'&nbsp;-&nbsp;0.3854G'&nbsp;+&nbsp;0.5B'</para>
795	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4542G'&nbsp;-&nbsp;0.0458B'</para>
796		  </listitem>
797		</varlistentry>
798	      </variablelist>
799	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
800	clamped to the range [-0.5&hellip;0.5].</para>
801	      <para>The default quantization is limited range, but full range is possible although
802	rarely seen.</para>
803	      <para>The <constant>V4L2_YCBCR_ENC_709</constant> encoding described above is the default
804	for this colorspace, but it can be overridden with <constant>V4L2_YCBCR_ENC_601</constant>, in which
805	case the BT.601 Y'CbCr encoding is used.</para>
806	      <variablelist>
807		<varlistentry>
808	      	  <term>The xvYCC 709 encoding (<constant>V4L2_YCBCR_ENC_XV709</constant>, <xref linkend="xvycc" />)
809	is similar to the Rec. 709 encoding, but it allows for R', G' and B' values that are outside the range
810	[0&hellip;1]. The resulting Y', Cb and Cr values are scaled and offset:</term>
811		  <listitem>
812	            <para>Y'&nbsp;=&nbsp;(219&nbsp;/&nbsp;255)&nbsp;*&nbsp;(0.2126R'&nbsp;+&nbsp;0.7152G'&nbsp;+&nbsp;0.0722B')&nbsp;+&nbsp;(16&nbsp;/&nbsp;255)</para>
813	            <para>Cb&nbsp;=&nbsp;(224&nbsp;/&nbsp;255)&nbsp;*&nbsp;(-0.1146R'&nbsp;-&nbsp;0.3854G'&nbsp;+&nbsp;0.5B')</para>
814	            <para>Cr&nbsp;=&nbsp;(224&nbsp;/&nbsp;255)&nbsp;*&nbsp;(0.5R'&nbsp;-&nbsp;0.4542G'&nbsp;-&nbsp;0.0458B')</para>
815		  </listitem>
816		</varlistentry>
817	      </variablelist>
818	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are clamped
819	to the range [-0.5&hellip;0.5]. The non-standard xvYCC 601 encoding can also be used by
820	selecting <constant>V4L2_YCBCR_ENC_XV601</constant>. The xvYCC encodings always use full
821	range quantization.</para>
822	    </section>
823	
824	    <section>
825	      <title id="col-srgb">Colorspace sRGB (<constant>V4L2_COLORSPACE_SRGB</constant>)</title>
826	      <para>The <xref linkend="srgb" /> standard defines the colorspace used by most webcams and computer graphics. The
827	default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SYCC</constant>. The default Y'CbCr quantization
828	is full range. The chromaticities of the primary colors and the white reference are:</para>
829	      <table frame="none">
830	        <title>sRGB Chromaticities</title>
831	        <tgroup cols="3" align="left">
832	          &cs-str;
833	    	<thead>
834	    	  <row>
835	    	    <entry>Color</entry>
836	    	    <entry>x</entry>
837	    	    <entry>y</entry>
838	    	  </row>
839	    	</thead>
840	          <tbody valign="top">
841	            <row>
842	              <entry>Red</entry>
843	              <entry>0.640</entry>
844	              <entry>0.330</entry>
845	            </row>
846	            <row>
847	              <entry>Green</entry>
848	              <entry>0.300</entry>
849	              <entry>0.600</entry>
850	            </row>
851	            <row>
852	              <entry>Blue</entry>
853	              <entry>0.150</entry>
854	              <entry>0.060</entry>
855	            </row>
856	            <row>
857	              <entry>White Reference (D65)</entry>
858	              <entry>0.3127</entry>
859	              <entry>0.3290</entry>
860	            </row>
861	          </tbody>
862	        </tgroup>
863	      </table>
864	      <para>These chromaticities are identical to the Rec. 709 colorspace.</para>
865	      <variablelist>
866		<varlistentry>
867	          <term>Transfer function. Note that negative values for L are only used by the Y'CbCr conversion.</term>
868		  <listitem>
869	            <para>L' = -1.055(-L)<superscript>1/2.4</superscript>&nbsp;+&nbsp;0.055&nbsp;for&nbsp;L&nbsp;&lt;&nbsp;-0.0031308</para>
870	            <para>L' = 12.92L&nbsp;for&nbsp;-0.0031308&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;0.0031308</para>
871	            <para>L' = 1.055L<superscript>1/2.4</superscript>&nbsp;-&nbsp;0.055&nbsp;for&nbsp;0.0031308&nbsp;&lt;&nbsp;L&nbsp;&le;&nbsp;1</para>
872		  </listitem>
873		</varlistentry>
874		<varlistentry>
875	          <term>Inverse Transfer function:</term>
876		  <listitem>
877	            <para>L = -((-L'&nbsp;+&nbsp;0.055)&nbsp;/&nbsp;1.055)<superscript>2.4</superscript>&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;-0.04045</para>
878	            <para>L = L'&nbsp;/&nbsp;12.92&nbsp;for&nbsp;-0.04045&nbsp;&le;&nbsp;L'&nbsp;&le;&nbsp;0.04045</para>
879	            <para>L = ((L'&nbsp;+&nbsp;0.055)&nbsp;/&nbsp;1.055)<superscript>2.4</superscript>&nbsp;for&nbsp;L'&nbsp;&gt;&nbsp;0.04045</para>
880		  </listitem>
881		</varlistentry>
882	      </variablelist>
883	      <variablelist>
884		<varlistentry>
885	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following
886	<constant>V4L2_YCBCR_ENC_SYCC</constant> encoding as defined by <xref linkend="sycc" />:</term>
887		  <listitem>
888	            <para>Y'&nbsp;=&nbsp;0.2990R'&nbsp;+&nbsp;0.5870G'&nbsp;+&nbsp;0.1140B'</para>
889	            <para>Cb&nbsp;=&nbsp;-0.1687R'&nbsp;-&nbsp;0.3313G'&nbsp;+&nbsp;0.5B'</para>
890	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4187G'&nbsp;-&nbsp;0.0813B'</para>
891		  </listitem>
892		</varlistentry>
893	      </variablelist>
894	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are clamped
895	to the range [-0.5&hellip;0.5]. The <constant>V4L2_YCBCR_ENC_SYCC</constant> quantization is always
896	full range. Although this Y'CbCr encoding looks very similar to the <constant>V4L2_YCBCR_ENC_XV601</constant>
897	encoding, it is not. The <constant>V4L2_YCBCR_ENC_XV601</constant> scales and offsets the Y'CbCr
898	values before quantization, but this encoding does not do that.</para>
899	    </section>
900	
901	    <section>
902	      <title id="col-adobergb">Colorspace Adobe RGB (<constant>V4L2_COLORSPACE_ADOBERGB</constant>)</title>
903	      <para>The <xref linkend="adobergb" /> standard defines the colorspace used by computer graphics
904	that use the AdobeRGB colorspace. This is also known as the <xref linkend="oprgb" /> standard.
905	The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. The default Y'CbCr
906	quantization is limited range. The chromaticities of the primary colors and the white reference
907	are:</para>
908	      <table frame="none">
909	        <title>Adobe RGB Chromaticities</title>
910	        <tgroup cols="3" align="left">
911	          &cs-str;
912	    	<thead>
913	    	  <row>
914	    	    <entry>Color</entry>
915	    	    <entry>x</entry>
916	    	    <entry>y</entry>
917	    	  </row>
918	    	</thead>
919	          <tbody valign="top">
920	            <row>
921	              <entry>Red</entry>
922	              <entry>0.6400</entry>
923	              <entry>0.3300</entry>
924	            </row>
925	            <row>
926	              <entry>Green</entry>
927	              <entry>0.2100</entry>
928	              <entry>0.7100</entry>
929	            </row>
930	            <row>
931	              <entry>Blue</entry>
932	              <entry>0.1500</entry>
933	              <entry>0.0600</entry>
934	            </row>
935	            <row>
936	              <entry>White Reference (D65)</entry>
937	              <entry>0.3127</entry>
938	              <entry>0.3290</entry>
939	            </row>
940	          </tbody>
941	        </tgroup>
942	      </table>
943	      <variablelist>
944		<varlistentry>
945	          <term>Transfer function:</term>
946		  <listitem>
947	            <para>L' = L<superscript>1/2.19921875</superscript></para>
948		  </listitem>
949		</varlistentry>
950		<varlistentry>
951	          <term>Inverse Transfer function:</term>
952		  <listitem>
953	            <para>L = L'<superscript>2.19921875</superscript></para>
954		  </listitem>
955		</varlistentry>
956	      </variablelist>
957	      <variablelist>
958		<varlistentry>
959	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
960	following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
961		  <listitem>
962	            <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
963	            <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
964	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
965		  </listitem>
966		</varlistentry>
967	      </variablelist>
968	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
969	clamped to the range [-0.5&hellip;0.5]. This transform is identical to one defined in
970	SMPTE 170M/BT.601. The Y'CbCr quantization is limited range.</para>
971	    </section>
972	
973	    <section>
974	      <title id="col-bt2020">Colorspace BT.2020 (<constant>V4L2_COLORSPACE_BT2020</constant>)</title>
975	      <para>The <xref linkend="itu2020" /> standard defines the colorspace used by Ultra-high definition
976	television (UHDTV). The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_BT2020</constant>.
977	The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and
978	the white reference are:</para>
979	      <table frame="none">
980	        <title>BT.2020 Chromaticities</title>
981	        <tgroup cols="3" align="left">
982	          &cs-str;
983	    	<thead>
984	    	  <row>
985	    	    <entry>Color</entry>
986	    	    <entry>x</entry>
987	    	    <entry>y</entry>
988	    	  </row>
989	    	</thead>
990	          <tbody valign="top">
991	            <row>
992	              <entry>Red</entry>
993	              <entry>0.708</entry>
994	              <entry>0.292</entry>
995	            </row>
996	            <row>
997	              <entry>Green</entry>
998	              <entry>0.170</entry>
999	              <entry>0.797</entry>
1000	            </row>
1001	            <row>
1002	              <entry>Blue</entry>
1003	              <entry>0.131</entry>
1004	              <entry>0.046</entry>
1005	            </row>
1006	            <row>
1007	              <entry>White Reference (D65)</entry>
1008	              <entry>0.3127</entry>
1009	              <entry>0.3290</entry>
1010	            </row>
1011	          </tbody>
1012	        </tgroup>
1013	      </table>
1014	      <variablelist>
1015		<varlistentry>
1016	          <term>Transfer function (same as Rec. 709):</term>
1017		  <listitem>
1018	            <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
1019	            <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
1020		  </listitem>
1021		</varlistentry>
1022		<varlistentry>
1023	          <term>Inverse Transfer function:</term>
1024		  <listitem>
1025	            <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
1026	            <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
1027		  </listitem>
1028		</varlistentry>
1029	      </variablelist>
1030	      <variablelist>
1031		<varlistentry>
1032	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
1033	following <constant>V4L2_YCBCR_ENC_BT2020</constant> encoding:</term>
1034		  <listitem>
1035	            <para>Y'&nbsp;=&nbsp;0.2627R'&nbsp;+&nbsp;0.6789G'&nbsp;+&nbsp;0.0593B'</para>
1036	            <para>Cb&nbsp;=&nbsp;-0.1396R'&nbsp;-&nbsp;0.3604G'&nbsp;+&nbsp;0.5B'</para>
1037	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4598G'&nbsp;-&nbsp;0.0402B'</para>
1038		  </listitem>
1039		</varlistentry>
1040	      </variablelist>
1041	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
1042	clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.</para>
1043	      <para>There is also an alternate constant luminance R'G'B' to Yc'CbcCrc
1044	(<constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant>) encoding:</para>
1045	      <variablelist>
1046		<varlistentry>
1047	      	  <term>Luma:</term>
1048		  <listitem>
1049	            <para>Yc'&nbsp;=&nbsp;(0.2627R&nbsp;+&nbsp;0.6789G&nbsp;+&nbsp;0.0593B)'</para>
1050		  </listitem>
1051		</varlistentry>
1052	      </variablelist>
1053	      <variablelist>
1054		<varlistentry>
1055	      	  <term>B'&nbsp;-&nbsp;Yc'&nbsp;&le;&nbsp;0:</term>
1056		  <listitem>
1057	            <para>Cbc&nbsp;=&nbsp;(B'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;1.9404</para>
1058		  </listitem>
1059		</varlistentry>
1060	      </variablelist>
1061	      <variablelist>
1062		<varlistentry>
1063	      	  <term>B'&nbsp;-&nbsp;Yc'&nbsp;&gt;&nbsp;0:</term>
1064		  <listitem>
1065	            <para>Cbc&nbsp;=&nbsp;(B'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;1.5816</para>
1066		  </listitem>
1067		</varlistentry>
1068	      </variablelist>
1069	      <variablelist>
1070		<varlistentry>
1071	      	  <term>R'&nbsp;-&nbsp;Yc'&nbsp;&le;&nbsp;0:</term>
1072		  <listitem>
1073	            <para>Crc&nbsp;=&nbsp;(R'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;1.7184</para>
1074		  </listitem>
1075		</varlistentry>
1076	      </variablelist>
1077	      <variablelist>
1078		<varlistentry>
1079	      	  <term>R'&nbsp;-&nbsp;Yc'&nbsp;&gt;&nbsp;0:</term>
1080		  <listitem>
1081	            <para>Crc&nbsp;=&nbsp;(R'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;0.9936</para>
1082		  </listitem>
1083		</varlistentry>
1084	      </variablelist>
1085	      <para>Yc' is clamped to the range [0&hellip;1] and Cbc and Crc are
1086	clamped to the range [-0.5&hellip;0.5]. The Yc'CbcCrc quantization is limited range.</para>
1087	    </section>
1088	
1089	    <section>
1090	      <title id="col-smpte-240m">Colorspace SMPTE 240M (<constant>V4L2_COLORSPACE_SMPTE240M</constant>)</title>
1091	      <para>The <xref linkend="smpte240m" /> standard was an interim standard used during the early days of HDTV (1988-1998).
1092	It has been superseded by Rec. 709. The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SMPTE240M</constant>.
1093	The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and the
1094	white reference are:</para>
1095	      <table frame="none">
1096	        <title>SMPTE 240M Chromaticities</title>
1097	        <tgroup cols="3" align="left">
1098	          &cs-str;
1099	    	<thead>
1100	    	  <row>
1101	    	    <entry>Color</entry>
1102	    	    <entry>x</entry>
1103	    	    <entry>y</entry>
1104	    	  </row>
1105	    	</thead>
1106	          <tbody valign="top">
1107	            <row>
1108	              <entry>Red</entry>
1109	              <entry>0.630</entry>
1110	              <entry>0.340</entry>
1111	            </row>
1112	            <row>
1113	              <entry>Green</entry>
1114	              <entry>0.310</entry>
1115	              <entry>0.595</entry>
1116	            </row>
1117	            <row>
1118	              <entry>Blue</entry>
1119	              <entry>0.155</entry>
1120	              <entry>0.070</entry>
1121	            </row>
1122	            <row>
1123	              <entry>White Reference (D65)</entry>
1124	              <entry>0.3127</entry>
1125	              <entry>0.3290</entry>
1126	            </row>
1127	          </tbody>
1128	        </tgroup>
1129	      </table>
1130	      <para>These chromaticities are identical to the SMPTE 170M colorspace.</para>
1131	      <variablelist>
1132		<varlistentry>
1133	          <term>Transfer function:</term>
1134		  <listitem>
1135	            <para>L' = 4L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.0228</para>
1136	            <para>L' = 1.1115L<superscript>0.45</superscript>&nbsp;-&nbsp;0.1115&nbsp;for&nbsp;0.0228&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
1137		  </listitem>
1138		</varlistentry>
1139		<varlistentry>
1140	          <term>Inverse Transfer function:</term>
1141		  <listitem>
1142	            <para>L = L'&nbsp;/&nbsp;4&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L'&nbsp;&lt;&nbsp;0.0913</para>
1143	            <para>L = ((L'&nbsp;+&nbsp;0.1115)&nbsp;/&nbsp;1.1115)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.0913</para>
1144		  </listitem>
1145		</varlistentry>
1146	      </variablelist>
1147	      <variablelist>
1148		<varlistentry>
1149	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
1150	following <constant>V4L2_YCBCR_ENC_SMPTE240M</constant> encoding:</term>
1151		  <listitem>
1152	            <para>Y'&nbsp;=&nbsp;0.2122R'&nbsp;+&nbsp;0.7013G'&nbsp;+&nbsp;0.0865B'</para>
1153	            <para>Cb&nbsp;=&nbsp;-0.1161R'&nbsp;-&nbsp;0.3839G'&nbsp;+&nbsp;0.5B'</para>
1154	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4451G'&nbsp;-&nbsp;0.0549B'</para>
1155		  </listitem>
1156		</varlistentry>
1157	      </variablelist>
1158	      <para>Yc' is clamped to the range [0&hellip;1] and Cbc and Crc are
1159	clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.</para>
1160	    </section>
1161	
1162	    <section>
1163	      <title id="col-sysm">Colorspace NTSC 1953 (<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant>)</title>
1164	      <para>This standard defines the colorspace used by NTSC in 1953. In practice this
1165	colorspace is obsolete and SMPTE 170M should be used instead. The default Y'CbCr encoding
1166	is <constant>V4L2_YCBCR_ENC_601</constant>. The default Y'CbCr quantization is limited range.
1167	The chromaticities of the primary colors and the white reference are:</para>
1168	      <table frame="none">
1169	        <title>NTSC 1953 Chromaticities</title>
1170	        <tgroup cols="3" align="left">
1171	          &cs-str;
1172	    	<thead>
1173	    	  <row>
1174	    	    <entry>Color</entry>
1175	    	    <entry>x</entry>
1176	    	    <entry>y</entry>
1177	    	  </row>
1178	    	</thead>
1179	          <tbody valign="top">
1180	            <row>
1181	              <entry>Red</entry>
1182	              <entry>0.67</entry>
1183	              <entry>0.33</entry>
1184	            </row>
1185	            <row>
1186	              <entry>Green</entry>
1187	              <entry>0.21</entry>
1188	              <entry>0.71</entry>
1189	            </row>
1190	            <row>
1191	              <entry>Blue</entry>
1192	              <entry>0.14</entry>
1193	              <entry>0.08</entry>
1194	            </row>
1195	            <row>
1196	              <entry>White Reference (C)</entry>
1197	              <entry>0.310</entry>
1198	              <entry>0.316</entry>
1199	            </row>
1200	          </tbody>
1201	        </tgroup>
1202	      </table>
1203	      <para>Note that this colorspace uses Illuminant C instead of D65 as the
1204	white reference. To correctly convert an image in this colorspace to another
1205	that uses D65 you need to apply a chromatic adaptation algorithm such as the
1206	Bradford method.</para>
1207	      <variablelist>
1208		<varlistentry>
1209	          <term>The transfer function was never properly defined for NTSC 1953. The
1210	Rec. 709 transfer function is recommended in the literature:</term>
1211		  <listitem>
1212	            <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
1213	            <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
1214		  </listitem>
1215		</varlistentry>
1216		<varlistentry>
1217	          <term>Inverse Transfer function:</term>
1218		  <listitem>
1219	            <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
1220	            <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
1221		  </listitem>
1222		</varlistentry>
1223	      </variablelist>
1224	      <variablelist>
1225		<varlistentry>
1226	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
1227	following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
1228		  <listitem>
1229	            <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
1230	            <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
1231	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
1232		  </listitem>
1233		</varlistentry>
1234	      </variablelist>
1235	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
1236	clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.
1237	This transform is identical to one defined in SMPTE 170M/BT.601.</para>
1238	    </section>
1239	
1240	    <section>
1241	      <title id="col-sysbg">Colorspace EBU Tech. 3213 (<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant>)</title>
1242	      <para>The <xref linkend="tech3213" /> standard defines the colorspace used by PAL/SECAM in 1975. In practice this
1243	colorspace is obsolete and SMPTE 170M should be used instead. The default Y'CbCr encoding
1244	is <constant>V4L2_YCBCR_ENC_601</constant>. The default Y'CbCr quantization is limited range.
1245	The chromaticities of the primary colors and the white reference are:</para>
1246	      <table frame="none">
1247	        <title>EBU Tech. 3213 Chromaticities</title>
1248	        <tgroup cols="3" align="left">
1249	          &cs-str;
1250	    	<thead>
1251	    	  <row>
1252	    	    <entry>Color</entry>
1253	    	    <entry>x</entry>
1254	    	    <entry>y</entry>
1255	    	  </row>
1256	    	</thead>
1257	          <tbody valign="top">
1258	            <row>
1259	              <entry>Red</entry>
1260	              <entry>0.64</entry>
1261	              <entry>0.33</entry>
1262	            </row>
1263	            <row>
1264	              <entry>Green</entry>
1265	              <entry>0.29</entry>
1266	              <entry>0.60</entry>
1267	            </row>
1268	            <row>
1269	              <entry>Blue</entry>
1270	              <entry>0.15</entry>
1271	              <entry>0.06</entry>
1272	            </row>
1273	            <row>
1274	              <entry>White Reference (D65)</entry>
1275	              <entry>0.3127</entry>
1276	              <entry>0.3290</entry>
1277	            </row>
1278	          </tbody>
1279	        </tgroup>
1280	      </table>
1281	      <variablelist>
1282		<varlistentry>
1283	          <term>The transfer function was never properly defined for this colorspace.
1284	The Rec. 709 transfer function is recommended in the literature:</term>
1285		  <listitem>
1286	            <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
1287	            <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
1288		  </listitem>
1289		</varlistentry>
1290		<varlistentry>
1291	          <term>Inverse Transfer function:</term>
1292		  <listitem>
1293	            <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
1294	            <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
1295		  </listitem>
1296		</varlistentry>
1297	      </variablelist>
1298	      <variablelist>
1299		<varlistentry>
1300	      	  <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
1301	following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
1302		  <listitem>
1303	            <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
1304	            <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
1305	            <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
1306		  </listitem>
1307		</varlistentry>
1308	      </variablelist>
1309	      <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
1310	clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.
1311	This transform is identical to one defined in SMPTE 170M/BT.601.</para>
1312	    </section>
1313	
1314	    <section>
1315	      <title id="col-jpeg">Colorspace JPEG (<constant>V4L2_COLORSPACE_JPEG</constant>)</title>
1316	      <para>This colorspace defines the colorspace used by most (Motion-)JPEG formats. The chromaticities
1317	of the primary colors and the white reference are identical to sRGB. The Y'CbCr encoding is
1318	<constant>V4L2_YCBCR_ENC_601</constant> with full range quantization where
1319	Y' is scaled to [0&hellip;255] and Cb/Cr are scaled to [-128&hellip;128] and
1320	then clipped to [-128&hellip;127].</para>
1321	      <para>Note that the JPEG standard does not actually store colorspace information.
1322	So if something other than sRGB is used, then the driver will have to set that information
1323	explicitly. Effectively <constant>V4L2_COLORSPACE_JPEG</constant> can be considered to be
1324	an abbreviation for <constant>V4L2_COLORSPACE_SRGB</constant>, <constant>V4L2_YCBCR_ENC_601</constant>
1325	and <constant>V4L2_QUANTIZATION_FULL_RANGE</constant>.</para>
1326	    </section>
1327	
1328	  </section>
1329	
1330	  <section id="pixfmt-indexed">
1331	    <title>Indexed Format</title>
1332	
1333	    <para>In this format each pixel is represented by an 8 bit index
1334	into a 256 entry ARGB palette. It is intended for <link
1335	linkend="osd">Video Output Overlays</link> only. There are no ioctls to
1336	access the palette, this must be done with ioctls of the Linux framebuffer API.</para>
1337	
1338	    <table pgwide="0" frame="none">
1339	      <title>Indexed Image Format</title>
1340	      <tgroup cols="37" align="center">
1341		<colspec colname="id" align="left" />
1342		<colspec colname="fourcc" />
1343		<colspec colname="bit" />
1344	
1345		<colspec colnum="4" colname="b07" align="center" />
1346		<colspec colnum="5" colname="b06" align="center" />
1347		<colspec colnum="6" colname="b05" align="center" />
1348		<colspec colnum="7" colname="b04" align="center" />
1349		<colspec colnum="8" colname="b03" align="center" />
1350		<colspec colnum="9" colname="b02" align="center" />
1351		<colspec colnum="10" colname="b01" align="center" />
1352		<colspec colnum="11" colname="b00" align="center" />
1353	
1354		<spanspec namest="b07" nameend="b00" spanname="b0" />
1355		<spanspec namest="b17" nameend="b10" spanname="b1" />
1356		<spanspec namest="b27" nameend="b20" spanname="b2" />
1357		<spanspec namest="b37" nameend="b30" spanname="b3" />
1358		<thead>
1359		  <row>
1360		    <entry>Identifier</entry>
1361		    <entry>Code</entry>
1362		    <entry>&nbsp;</entry>
1363		    <entry spanname="b0">Byte&nbsp;0</entry>
1364		  </row>
1365		  <row>
1366		    <entry>&nbsp;</entry>
1367		    <entry>&nbsp;</entry>
1368		    <entry>Bit</entry>
1369		    <entry>7</entry>
1370		    <entry>6</entry>
1371		    <entry>5</entry>
1372		    <entry>4</entry>
1373		    <entry>3</entry>
1374		    <entry>2</entry>
1375		    <entry>1</entry>
1376		    <entry>0</entry>
1377		  </row>
1378		</thead>
1379		<tbody valign="top">
1380		  <row id="V4L2-PIX-FMT-PAL8">
1381		    <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry>
1382		    <entry>'PAL8'</entry>
1383		    <entry></entry>
1384		    <entry>i<subscript>7</subscript></entry>
1385		    <entry>i<subscript>6</subscript></entry>
1386		    <entry>i<subscript>5</subscript></entry>
1387		    <entry>i<subscript>4</subscript></entry>
1388		    <entry>i<subscript>3</subscript></entry>
1389		    <entry>i<subscript>2</subscript></entry>
1390		    <entry>i<subscript>1</subscript></entry>
1391		    <entry>i<subscript>0</subscript></entry>
1392		  </row>
1393		</tbody>
1394	      </tgroup>
1395	    </table>
1396	  </section>
1397	
1398	  <section id="pixfmt-rgb">
1399	    <title>RGB Formats</title>
1400	
1401	    &sub-packed-rgb;
1402	    &sub-sbggr8;
1403	    &sub-sgbrg8;
1404	    &sub-sgrbg8;
1405	    &sub-srggb8;
1406	    &sub-sbggr16;
1407	    &sub-srggb10;
1408	    &sub-srggb10p;
1409	    &sub-srggb10alaw8;
1410	    &sub-srggb10dpcm8;
1411	    &sub-srggb12;
1412	  </section>
1413	
1414	  <section id="yuv-formats">
1415	    <title>YUV Formats</title>
1416	
1417	    <para>YUV is the format native to TV broadcast and composite video
1418	signals. It separates the brightness information (Y) from the color
1419	information (U and V or Cb and Cr). The color information consists of
1420	red and blue <emphasis>color difference</emphasis> signals, this way
1421	the green component can be reconstructed by subtracting from the
1422	brightness component. See <xref linkend="colorspaces" /> for conversion
1423	examples. YUV was chosen because early television would only transmit
1424	brightness information. To add color in a way compatible with existing
1425	receivers a new signal carrier was added to transmit the color
1426	difference signals. Secondary in the YUV format the U and V components
1427	usually have lower resolution than the Y component. This is an analog
1428	video compression technique taking advantage of a property of the
1429	human visual system, being more sensitive to brightness
1430	information.</para>
1431	
1432	    &sub-packed-yuv;
1433	    &sub-grey;
1434	    &sub-y10;
1435	    &sub-y12;
1436	    &sub-y10b;
1437	    &sub-y16;
1438	    &sub-uv8;
1439	    &sub-yuyv;
1440	    &sub-uyvy;
1441	    &sub-yvyu;
1442	    &sub-vyuy;
1443	    &sub-y41p;
1444	    &sub-yuv420;
1445	    &sub-yuv420m;
1446	    &sub-yvu420m;
1447	    &sub-yuv410;
1448	    &sub-yuv422p;
1449	    &sub-yuv411p;
1450	    &sub-nv12;
1451	    &sub-nv12m;
1452	    &sub-nv12mt;
1453	    &sub-nv16;
1454	    &sub-nv16m;
1455	    &sub-nv24;
1456	    &sub-m420;
1457	  </section>
1458	
1459	  <section>
1460	    <title>Compressed Formats</title>
1461	
1462	    <table pgwide="1" frame="none" id="compressed-formats">
1463	      <title>Compressed Image Formats</title>
1464	      <tgroup cols="3" align="left">
1465		&cs-def;
1466		<thead>
1467		  <row>
1468		    <entry>Identifier</entry>
1469		    <entry>Code</entry>
1470		    <entry>Details</entry>
1471		  </row>
1472		</thead>
1473		<tbody valign="top">
1474		 <row id="V4L2-PIX-FMT-JPEG">
1475		    <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry>
1476		    <entry>'JPEG'</entry>
1477		    <entry>TBD. See also &VIDIOC-G-JPEGCOMP;,
1478		    &VIDIOC-S-JPEGCOMP;.</entry>
1479		  </row>
1480		  <row id="V4L2-PIX-FMT-MPEG">
1481		    <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry>
1482		    <entry>'MPEG'</entry>
1483		    <entry>MPEG multiplexed stream. The actual format is determined by
1484	extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
1485	<xref linkend="mpeg-control-id" />.</entry>
1486		  </row>
1487		  <row id="V4L2-PIX-FMT-H264">
1488			<entry><constant>V4L2_PIX_FMT_H264</constant></entry>
1489			<entry>'H264'</entry>
1490			<entry>H264 video elementary stream with start codes.</entry>
1491		  </row>
1492		  <row id="V4L2-PIX-FMT-H264-NO-SC">
1493			<entry><constant>V4L2_PIX_FMT_H264_NO_SC</constant></entry>
1494			<entry>'AVC1'</entry>
1495			<entry>H264 video elementary stream without start codes.</entry>
1496		  </row>
1497		  <row id="V4L2-PIX-FMT-H264-MVC">
1498			<entry><constant>V4L2_PIX_FMT_H264_MVC</constant></entry>
1499			<entry>'M264'</entry>
1500			<entry>H264 MVC video elementary stream.</entry>
1501		  </row>
1502		  <row id="V4L2-PIX-FMT-H263">
1503			<entry><constant>V4L2_PIX_FMT_H263</constant></entry>
1504			<entry>'H263'</entry>
1505			<entry>H263 video elementary stream.</entry>
1506		  </row>
1507		  <row id="V4L2-PIX-FMT-MPEG1">
1508			<entry><constant>V4L2_PIX_FMT_MPEG1</constant></entry>
1509			<entry>'MPG1'</entry>
1510			<entry>MPEG1 video elementary stream.</entry>
1511		  </row>
1512		  <row id="V4L2-PIX-FMT-MPEG2">
1513			<entry><constant>V4L2_PIX_FMT_MPEG2</constant></entry>
1514			<entry>'MPG2'</entry>
1515			<entry>MPEG2 video elementary stream.</entry>
1516		  </row>
1517		  <row id="V4L2-PIX-FMT-MPEG4">
1518			<entry><constant>V4L2_PIX_FMT_MPEG4</constant></entry>
1519			<entry>'MPG4'</entry>
1520			<entry>MPEG4 video elementary stream.</entry>
1521		  </row>
1522		  <row id="V4L2-PIX-FMT-XVID">
1523			<entry><constant>V4L2_PIX_FMT_XVID</constant></entry>
1524			<entry>'XVID'</entry>
1525			<entry>Xvid video elementary stream.</entry>
1526		  </row>
1527		  <row id="V4L2-PIX-FMT-VC1-ANNEX-G">
1528			<entry><constant>V4L2_PIX_FMT_VC1_ANNEX_G</constant></entry>
1529			<entry>'VC1G'</entry>
1530			<entry>VC1, SMPTE 421M Annex G compliant stream.</entry>
1531		  </row>
1532		  <row id="V4L2-PIX-FMT-VC1-ANNEX-L">
1533			<entry><constant>V4L2_PIX_FMT_VC1_ANNEX_L</constant></entry>
1534			<entry>'VC1L'</entry>
1535			<entry>VC1, SMPTE 421M Annex L compliant stream.</entry>
1536		  </row>
1537		  <row id="V4L2-PIX-FMT-VP8">
1538			<entry><constant>V4L2_PIX_FMT_VP8</constant></entry>
1539			<entry>'VP80'</entry>
1540			<entry>VP8 video elementary stream.</entry>
1541		  </row>
1542		</tbody>
1543	      </tgroup>
1544	    </table>
1545	  </section>
1546	
1547	  <section id="sdr-formats">
1548	    <title>SDR Formats</title>
1549	
1550	    <para>These formats are used for <link linkend="sdr">SDR Capture</link>
1551	interface only.</para>
1552	
1553	    &sub-sdr-cu08;
1554	    &sub-sdr-cu16le;
1555	    &sub-sdr-cs08;
1556	    &sub-sdr-cs14le;
1557	    &sub-sdr-ru12le;
1558	
1559	  </section>
1560	
1561	  <section id="pixfmt-reserved">
1562	    <title>Reserved Format Identifiers</title>
1563	
1564	    <para>These formats are not defined by this specification, they
1565	are just listed for reference and to avoid naming conflicts. If you
1566	want to register your own format, send an e-mail to the linux-media mailing
1567	list &v4l-ml; for inclusion in the <filename>videodev2.h</filename>
1568	file. If you want to share your format with other developers add a
1569	link to your documentation and send a copy to the linux-media mailing list
1570	for inclusion in this section. If you think your format should be listed
1571	in a standard format section please make a proposal on the linux-media mailing
1572	list.</para>
1573	
1574	    <table pgwide="1" frame="none" id="reserved-formats">
1575	      <title>Reserved Image Formats</title>
1576	      <tgroup cols="3" align="left">
1577		&cs-def;
1578		<thead>
1579		  <row>
1580		    <entry>Identifier</entry>
1581		    <entry>Code</entry>
1582		    <entry>Details</entry>
1583		  </row>
1584		</thead>
1585		<tbody valign="top">
1586		  <row id="V4L2-PIX-FMT-DV">
1587		    <entry><constant>V4L2_PIX_FMT_DV</constant></entry>
1588		    <entry>'dvsd'</entry>
1589		    <entry>unknown</entry>
1590		  </row>
1591		  <row id="V4L2-PIX-FMT-ET61X251">
1592		    <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry>
1593		    <entry>'E625'</entry>
1594		    <entry>Compressed format of the ET61X251 driver.</entry>
1595		  </row>
1596		  <row id="V4L2-PIX-FMT-HI240">
1597		    <entry><constant>V4L2_PIX_FMT_HI240</constant></entry>
1598		    <entry>'HI24'</entry>
1599		    <entry><para>8 bit RGB format used by the BTTV driver.</para></entry>
1600		  </row>
1601		  <row id="V4L2-PIX-FMT-HM12">
1602		    <entry><constant>V4L2_PIX_FMT_HM12</constant></entry>
1603		    <entry>'HM12'</entry>
1604		    <entry><para>YUV 4:2:0 format used by the
1605	IVTV driver, <ulink url="http://www.ivtvdriver.org/">
1606	http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the
1607	kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename>
1608	</para></entry>
1609		  </row>
1610		  <row id="V4L2-PIX-FMT-CPIA1">
1611		    <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry>
1612		    <entry>'CPIA'</entry>
1613		    <entry>YUV format used by the gspca cpia1 driver.</entry>
1614		  </row>
1615		  <row id="V4L2-PIX-FMT-JPGL">
1616		    <entry><constant>V4L2_PIX_FMT_JPGL</constant></entry>
1617		    <entry>'JPGL'</entry>
1618		    <entry>JPEG-Light format (Pegasus Lossless JPEG)
1619				used in Divio webcams NW 80x.</entry>
1620		  </row>
1621		  <row id="V4L2-PIX-FMT-SPCA501">
1622		    <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry>
1623		    <entry>'S501'</entry>
1624		    <entry>YUYV per line used by the gspca driver.</entry>
1625		  </row>
1626		  <row id="V4L2-PIX-FMT-SPCA505">
1627		    <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry>
1628		    <entry>'S505'</entry>
1629		    <entry>YYUV per line used by the gspca driver.</entry>
1630		  </row>
1631		  <row id="V4L2-PIX-FMT-SPCA508">
1632		    <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry>
1633		    <entry>'S508'</entry>
1634		    <entry>YUVY per line used by the gspca driver.</entry>
1635		  </row>
1636		  <row id="V4L2-PIX-FMT-SPCA561">
1637		    <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry>
1638		    <entry>'S561'</entry>
1639		    <entry>Compressed GBRG Bayer format used by the gspca driver.</entry>
1640		  </row>
1641		  <row id="V4L2-PIX-FMT-PAC207">
1642		    <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry>
1643		    <entry>'P207'</entry>
1644		    <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
1645		  </row>
1646		  <row id="V4L2-PIX-FMT-MR97310A">
1647		    <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry>
1648		    <entry>'M310'</entry>
1649		    <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
1650		  </row>
1651		  <row id="V4L2-PIX-FMT-JL2005BCD">
1652		    <entry><constant>V4L2_PIX_FMT_JL2005BCD</constant></entry>
1653		    <entry>'JL20'</entry>
1654		    <entry>JPEG compressed RGGB Bayer format used by the gspca driver.</entry>
1655		  </row>
1656		  <row id="V4L2-PIX-FMT-OV511">
1657		    <entry><constant>V4L2_PIX_FMT_OV511</constant></entry>
1658		    <entry>'O511'</entry>
1659		    <entry>OV511 JPEG format used by the gspca driver.</entry>
1660		  </row>
1661		  <row id="V4L2-PIX-FMT-OV518">
1662		    <entry><constant>V4L2_PIX_FMT_OV518</constant></entry>
1663		    <entry>'O518'</entry>
1664		    <entry>OV518 JPEG format used by the gspca driver.</entry>
1665		  </row>
1666		  <row id="V4L2-PIX-FMT-PJPG">
1667		    <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry>
1668		    <entry>'PJPG'</entry>
1669		    <entry>Pixart 73xx JPEG format used by the gspca driver.</entry>
1670		  </row>
1671		  <row id="V4L2-PIX-FMT-SE401">
1672		    <entry><constant>V4L2_PIX_FMT_SE401</constant></entry>
1673		    <entry>'S401'</entry>
1674		    <entry>Compressed RGB format used by the gspca se401 driver</entry>
1675		  </row>
1676		  <row id="V4L2-PIX-FMT-SQ905C">
1677		    <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry>
1678		    <entry>'905C'</entry>
1679		    <entry>Compressed RGGB bayer format used by the gspca driver.</entry>
1680		  </row>
1681		  <row id="V4L2-PIX-FMT-MJPEG">
1682		    <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry>
1683		    <entry>'MJPG'</entry>
1684		    <entry>Compressed format used by the Zoran driver</entry>
1685		  </row>
1686		  <row id="V4L2-PIX-FMT-PWC1">
1687		    <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry>
1688		    <entry>'PWC1'</entry>
1689		    <entry>Compressed format of the PWC driver.</entry>
1690		  </row>
1691		  <row id="V4L2-PIX-FMT-PWC2">
1692		    <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry>
1693		    <entry>'PWC2'</entry>
1694		    <entry>Compressed format of the PWC driver.</entry>
1695		  </row>
1696		  <row id="V4L2-PIX-FMT-SN9C10X">
1697		    <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry>
1698		    <entry>'S910'</entry>
1699		    <entry>Compressed format of the SN9C102 driver.</entry>
1700		  </row>
1701		  <row id="V4L2-PIX-FMT-SN9C20X-I420">
1702		    <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry>
1703		    <entry>'S920'</entry>
1704		    <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry>
1705		  </row>
1706		  <row id="V4L2-PIX-FMT-SN9C2028">
1707		    <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry>
1708		    <entry>'SONX'</entry>
1709		    <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry>
1710		  </row>
1711		  <row id="V4L2-PIX-FMT-STV0680">
1712		    <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry>
1713		    <entry>'S680'</entry>
1714		    <entry>Bayer format of the gspca stv0680 driver.</entry>
1715		  </row>
1716		  <row id="V4L2-PIX-FMT-WNVA">
1717		    <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry>
1718		    <entry>'WNVA'</entry>
1719		    <entry><para>Used by the Winnov Videum driver, <ulink
1720	url="http://www.thedirks.org/winnov/">
1721	http://www.thedirks.org/winnov/</ulink></para></entry>
1722		  </row>
1723		  <row id="V4L2-PIX-FMT-TM6000">
1724		    <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry>
1725		    <entry>'TM60'</entry>
1726		    <entry><para>Used by Trident tm6000</para></entry>
1727		  </row>
1728		  <row id="V4L2-PIX-FMT-CIT-YYVYUY">
1729		    <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry>
1730		    <entry>'CITV'</entry>
1731		    <entry><para>Used by xirlink CIT, found at IBM webcams.</para>
1732		           <para>Uses one line of Y then 1 line of VYUY</para>
1733		    </entry>
1734		  </row>
1735		  <row id="V4L2-PIX-FMT-KONICA420">
1736		    <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry>
1737		    <entry>'KONI'</entry>
1738		    <entry><para>Used by Konica webcams.</para>
1739		           <para>YUV420 planar in blocks of 256 pixels.</para>
1740		    </entry>
1741		  </row>
1742		  <row id="V4L2-PIX-FMT-YYUV">
1743		    <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
1744		    <entry>'YYUV'</entry>
1745		    <entry>unknown</entry>
1746		  </row>
1747		  <row id="V4L2-PIX-FMT-Y4">
1748		    <entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
1749		    <entry>'Y04 '</entry>
1750		    <entry>Old 4-bit greyscale format. Only the most significant 4 bits of each byte are used,
1751	the other bits are set to 0.</entry>
1752		  </row>
1753		  <row id="V4L2-PIX-FMT-Y6">
1754		    <entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
1755		    <entry>'Y06 '</entry>
1756		    <entry>Old 6-bit greyscale format. Only the most significant 6 bits of each byte are used,
1757	the other bits are set to 0.</entry>
1758		  </row>
1759		  <row id="V4L2-PIX-FMT-S5C-UYVY-JPG">
1760		    <entry><constant>V4L2_PIX_FMT_S5C_UYVY_JPG</constant></entry>
1761		    <entry>'S5CI'</entry>
1762		    <entry>Two-planar format used by Samsung S5C73MX cameras. The
1763	first plane contains interleaved JPEG and UYVY image data, followed by meta data
1764	in form of an array of offsets to the UYVY data blocks. The actual pointer array
1765	follows immediately the interleaved JPEG/UYVY data, the number of entries in
1766	this array equals the height of the UYVY image. Each entry is a 4-byte unsigned
1767	integer in big endian order and it's an offset to a single pixel line of the
1768	UYVY image. The first plane can start either with JPEG or UYVY data chunk. The
1769	size of a single UYVY block equals the UYVY image's width multiplied by 2. The
1770	size of a JPEG chunk depends on the image and can vary with each line.
1771	<para>The second plane, at an offset of 4084 bytes, contains a 4-byte offset to
1772	the pointer array in the first plane. This offset is followed by a 4-byte value
1773	indicating size of the pointer array. All numbers in the second plane are also
1774	in big endian order. Remaining data in the second plane is undefined. The
1775	information in the second plane allows to easily find location of the pointer
1776	array, which can be different for each frame. The size of the pointer array is
1777	constant for given UYVY image height.</para>
1778	<para>In order to extract UYVY and JPEG frames an application can initially set
1779	a data pointer to the start of first plane and then add an offset from the first
1780	entry of the pointers table. Such a pointer indicates start of an UYVY image
1781	pixel line. Whole UYVY line can be copied to a separate buffer. These steps
1782	should be repeated for each line, i.e. the number of entries in the pointer
1783	array. Anything what's in between the UYVY lines is JPEG data and should be
1784	concatenated to form the JPEG stream. </para>
1785	</entry>
1786		  </row>
1787		</tbody>
1788	      </tgroup>
1789	    </table>
1790	
1791	    <table frame="none" pgwide="1" id="format-flags">
1792	      <title>Format Flags</title>
1793	      <tgroup cols="3">
1794		&cs-def;
1795		<tbody valign="top">
1796		  <row>
1797		    <entry><constant>V4L2_PIX_FMT_FLAG_PREMUL_ALPHA</constant></entry>
1798		    <entry>0x00000001</entry>
1799		    <entry>The color values are premultiplied by the alpha channel
1800	value. For example, if a light blue pixel with 50% transparency was described by
1801	RGBA values (128, 192, 255, 128), the same pixel described with premultiplied
1802	colors would be described by RGBA values (64, 96, 128, 128) </entry>
1803		  </row>
1804		</tbody>
1805	      </tgroup>
1806	    </table>
1807	  </section>
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.