tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1 <title>Image Formats</title>
2
3 <para>The V4L2 API was primarily designed for devices exchanging
4image 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.
7The former is used with the single-planar API, while the latter is used with the
8multi-planar version (see <xref linkend="planar-apis"/>). Image formats are
9negotiated with the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video
10capturing 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.</entry>
29 </row>
30 <row>
31 <entry spanname="hspan">Applications set these fields to
32request an image size, drivers return the closest possible values. In
33case of planar formats the <structfield>width</structfield> and
34<structfield>height</structfield> applies to the largest plane. To
35avoid ambiguities drivers must return values rounded up to a multiple
36of the scale factor of any smaller planes. For example when the image
37format is YUV 4:2:0, <structfield>width</structfield> and
38<structfield>height</structfield> must be multiples of two.</entry>
39 </row>
40 <row>
41 <entry>__u32</entry>
42 <entry><structfield>pixelformat</structfield></entry>
43 <entry>The pixel format or type of compression, set by the
44application. This is a little endian <link
45linkend="v4l2-fourcc">four character code</link>. V4L2 defines
46standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
47linkend="yuv-formats" />, and reserved codes in <xref
48linkend="reserved-formats" /></entry>
49 </row>
50 <row>
51 <entry>&v4l2-field;</entry>
52 <entry><structfield>field</structfield></entry>
53 <entry>Video images are typically interlaced. Applications
54can request to capture or output only the top or bottom field, or both
55fields interlaced or sequentially stored in one buffer or alternating
56in separate buffers. Drivers return the actual field order selected.
57For details see <xref linkend="field-order" />.</entry>
58 </row>
59 <row>
60 <entry>__u32</entry>
61 <entry><structfield>bytesperline</structfield></entry>
62 <entry>Distance in bytes between the leftmost pixels in two
63adjacent lines.</entry>
64 </row>
65 <row>
66 <entry spanname="hspan"><para>Both applications and drivers
67can set this field to request padding bytes at the end of each line.
68Drivers however may ignore the value requested by the application,
69returning <structfield>width</structfield> times bytes per pixel or a
70larger value required by the hardware. That implies applications can
71just set this field to zero to get a reasonable
72default.</para><para>Video hardware may access padding bytes,
73therefore they must reside in accessible memory. Consider cases where
74padding bytes after the last line of an image cross a system page
75boundary. Input devices may write padding bytes, the value is
76undefined. Output devices ignore the contents of padding
77bytes.</para><para>When the image format is planar the
78<structfield>bytesperline</structfield> value applies to the largest
79plane and is divided by the same factor as the
80<structfield>width</structfield> field for any smaller planes. For
81example the Cb and Cr planes of a YUV 4:2:0 image have half as many
82padding bytes following each line as the Y plane. To avoid ambiguities
83drivers must return a <structfield>bytesperline</structfield> value
84rounded up to a multiple of the scale factor.</para></entry>
85 </row>
86 <row>
87 <entry>__u32</entry>
88 <entry><structfield>sizeimage</structfield></entry>
89 <entry>Size in bytes of the buffer to hold a complete image,
90set by the driver. Usually this is
91<structfield>bytesperline</structfield> times
92<structfield>height</structfield>. When the image consists of variable
93length compressed data this is the maximum number of bytes required to
94hold an image.</entry>
95 </row>
96 <row>
97 <entry>&v4l2-colorspace;</entry>
98 <entry><structfield>colorspace</structfield></entry>
99 <entry>This information supplements the
100<structfield>pixelformat</structfield> and must be set by the driver,
101see <xref linkend="colorspaces" />.</entry>
102 </row>
103 <row>
104 <entry>__u32</entry>
105 <entry><structfield>priv</structfield></entry>
106 <entry>Reserved for custom (driver defined) additional
107information about formats. When not used drivers and applications must
108set this field to zero.</entry>
109 </row>
110 </tbody>
111 </tgroup>
112 </table>
113</section>
114
115<section>
116 <title>Multi-planar format structures</title>
117 <para>The <structname>v4l2_plane_pix_format</structname> structures define
118 size and layout for each of the planes in a multi-planar format.
119 The <structname>v4l2_pix_format_mplane</structname> structure contains
120 information common to all planes (such as image width and height) and
121 an array of <structname>v4l2_plane_pix_format</structname> structures,
122 describing all planes of that format.</para>
123 <table pgwide="1" frame="none" id="v4l2-plane-pix-format">
124 <title>struct <structname>v4l2_plane_pix_format</structname></title>
125 <tgroup cols="3">
126 &cs-str;
127 <tbody valign="top">
128 <row>
129 <entry>__u32</entry>
130 <entry><structfield>sizeimage</structfield></entry>
131 <entry>Maximum size in bytes required for image data in this plane.
132 </entry>
133 </row>
134 <row>
135 <entry>__u16</entry>
136 <entry><structfield>bytesperline</structfield></entry>
137 <entry>Distance in bytes between the leftmost pixels in two adjacent
138 lines.</entry>
139 </row>
140 <row>
141 <entry>__u16</entry>
142 <entry><structfield>reserved[7]</structfield></entry>
143 <entry>Reserved for future extensions. Should be zeroed by the
144 application.</entry>
145 </row>
146 </tbody>
147 </tgroup>
148 </table>
149 <table pgwide="1" frame="none" id="v4l2-pix-format-mplane">
150 <title>struct <structname>v4l2_pix_format_mplane</structname></title>
151 <tgroup cols="3">
152 &cs-str;
153 <tbody valign="top">
154 <row>
155 <entry>__u32</entry>
156 <entry><structfield>width</structfield></entry>
157 <entry>Image width in pixels.</entry>
158 </row>
159 <row>
160 <entry>__u32</entry>
161 <entry><structfield>height</structfield></entry>
162 <entry>Image height in pixels.</entry>
163 </row>
164 <row>
165 <entry>__u32</entry>
166 <entry><structfield>pixelformat</structfield></entry>
167 <entry>The pixel format. Both single- and multi-planar four character
168codes can be used.</entry>
169 </row>
170 <row>
171 <entry>&v4l2-field;</entry>
172 <entry><structfield>field</structfield></entry>
173 <entry>See &v4l2-pix-format;.</entry>
174 </row>
175 <row>
176 <entry>&v4l2-colorspace;</entry>
177 <entry><structfield>colorspace</structfield></entry>
178 <entry>See &v4l2-pix-format;.</entry>
179 </row>
180 <row>
181 <entry>&v4l2-plane-pix-format;</entry>
182 <entry><structfield>plane_fmt[VIDEO_MAX_PLANES]</structfield></entry>
183 <entry>An array of structures describing format of each plane this
184 pixel format consists of. The number of valid entries in this array
185 has to be put in the <structfield>num_planes</structfield>
186 field.</entry>
187 </row>
188 <row>
189 <entry>__u8</entry>
190 <entry><structfield>num_planes</structfield></entry>
191 <entry>Number of planes (i.e. separate memory buffers) for this format
192 and the number of valid entries in the
193 <structfield>plane_fmt</structfield> array.</entry>
194 </row>
195 <row>
196 <entry>__u8</entry>
197 <entry><structfield>reserved[11]</structfield></entry>
198 <entry>Reserved for future extensions. Should be zeroed by the
199 application.</entry>
200 </row>
201 </tbody>
202 </tgroup>
203 </table>
204</section>
205
206 <section>
207 <title>Standard Image Formats</title>
208
209 <para>In order to exchange images between drivers and
210applications, it is necessary to have standard image data formats
211which both sides will interpret the same way. V4L2 includes several
212such formats, and this section is intended to be an unambiguous
213specification of the standard image data formats in V4L2.</para>
214
215 <para>V4L2 drivers are not limited to these formats, however.
216Driver-specific formats are possible. In that case the application may
217depend on a codec to convert images to one of the standard formats
218when needed. But the data can still be stored and retrieved in the
219proprietary format. For example, a device may support a proprietary
220compressed format. Applications can still capture and save the data in
221the compressed format, saving much disk space, and later use a codec
222to convert the images to the X Windows screen format when the video is
223to be displayed.</para>
224
225 <para>Even so, ultimately, some standard formats are needed, so
226the V4L2 specification would not be complete without well-defined
227standard formats.</para>
228
229 <para>The V4L2 standard formats are mainly uncompressed formats. The
230pixels are always arranged in memory from left to right, and from top
231to bottom. The first byte of data in the image buffer is always for
232the leftmost pixel of the topmost row. Following that is the pixel
233immediately to its right, and so on until the end of the top row of
234pixels. Following the rightmost pixel of the row there may be zero or
235more bytes of padding to guarantee that each row of pixel data has a
236certain alignment. Following the pad bytes, if any, is data for the
237leftmost pixel of the second row from the top, and so on. The last row
238has just as many pad bytes after it as the other rows.</para>
239
240 <para>In V4L2 each format has an identifier which looks like
241<constant>PIX_FMT_XXX</constant>, defined in the <link
242linkend="videodev">videodev.h</link> header file. These identifiers
243represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link>
244which are also listed below, however they are not the same as those
245used in the Windows world.</para>
246
247 <para>For some formats, data is stored in separate, discontiguous
248memory buffers. Those formats are identified by a separate set of FourCC codes
249and are referred to as "multi-planar formats". For example, a YUV422 frame is
250normally stored in one memory buffer, but it can also be placed in two or three
251separate buffers, with Y component in one buffer and CbCr components in another
252in the 2-planar version or with each component in its own buffer in the
2533-planar case. Those sub-buffers are referred to as "planes".</para>
254 </section>
255
256 <section id="colorspaces">
257 <title>Colorspaces</title>
258
259 <para>[intro]</para>
260
261 <!-- See proposal by Billy Biggs, video4linux-list@redhat.com
262on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and
263http://vektor.theorem.ca/graphics/ycbcr/ and
264http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html -->
265
266 <para>
267 <variablelist>
268 <varlistentry>
269 <term>Gamma Correction</term>
270 <listitem>
271 <para>[to do]</para>
272 <para>E'<subscript>R</subscript> = f(R)</para>
273 <para>E'<subscript>G</subscript> = f(G)</para>
274 <para>E'<subscript>B</subscript> = f(B)</para>
275 </listitem>
276 </varlistentry>
277 <varlistentry>
278 <term>Construction of luminance and color-difference
279signals</term>
280 <listitem>
281 <para>[to do]</para>
282 <para>E'<subscript>Y</subscript> =
283Coeff<subscript>R</subscript> E'<subscript>R</subscript>
284+ Coeff<subscript>G</subscript> E'<subscript>G</subscript>
285+ Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
286 <para>(E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = E'<subscript>R</subscript>
287- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
288- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
289- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
290 <para>(E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = E'<subscript>B</subscript>
291- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
292- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
293- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
294 </listitem>
295 </varlistentry>
296 <varlistentry>
297 <term>Re-normalized color-difference signals</term>
298 <listitem>
299 <para>The color-difference signals are scaled back to unity
300range [-0.5;+0.5]:</para>
301 <para>K<subscript>B</subscript> = 0.5 / (1 - Coeff<subscript>B</subscript>)</para>
302 <para>K<subscript>R</subscript> = 0.5 / (1 - Coeff<subscript>R</subscript>)</para>
303 <para>P<subscript>B</subscript> =
304K<subscript>B</subscript> (E'<subscript>B</subscript> - E'<subscript>Y</subscript>) =
305 0.5 (Coeff<subscript>R</subscript> / Coeff<subscript>B</subscript>) E'<subscript>R</subscript>
306+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>B</subscript>) E'<subscript>G</subscript>
307+ 0.5 E'<subscript>B</subscript></para>
308 <para>P<subscript>R</subscript> =
309K<subscript>R</subscript> (E'<subscript>R</subscript> - E'<subscript>Y</subscript>) =
310 0.5 E'<subscript>R</subscript>
311+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>R</subscript>) E'<subscript>G</subscript>
312+ 0.5 (Coeff<subscript>B</subscript> / Coeff<subscript>R</subscript>) E'<subscript>B</subscript></para>
313 </listitem>
314 </varlistentry>
315 <varlistentry>
316 <term>Quantization</term>
317 <listitem>
318 <para>[to do]</para>
319 <para>Y' = (Lum. Levels - 1) · E'<subscript>Y</subscript> + Lum. Offset</para>
320 <para>C<subscript>B</subscript> = (Chrom. Levels - 1)
321· P<subscript>B</subscript> + Chrom. Offset</para>
322 <para>C<subscript>R</subscript> = (Chrom. Levels - 1)
323· P<subscript>R</subscript> + Chrom. Offset</para>
324 <para>Rounding to the nearest integer and clamping to the range
325[0;255] finally yields the digital color components Y'CbCr
326stored in YUV images.</para>
327 </listitem>
328 </varlistentry>
329 </variablelist>
330 </para>
331
332 <example>
333 <title>ITU-R Rec. BT.601 color conversion</title>
334
335 <para>Forward Transformation</para>
336
337 <programlisting>
338int ER, EG, EB; /* gamma corrected RGB input [0;255] */
339int Y1, Cb, Cr; /* output [0;255] */
340
341double r, g, b; /* temporaries */
342double y1, pb, pr;
343
344int
345clamp (double x)
346{
347 int r = x; /* round to nearest */
348
349 if (r < 0) return 0;
350 else if (r > 255) return 255;
351 else return r;
352}
353
354r = ER / 255.0;
355g = EG / 255.0;
356b = EB / 255.0;
357
358y1 = 0.299 * r + 0.587 * g + 0.114 * b;
359pb = -0.169 * r - 0.331 * g + 0.5 * b;
360pr = 0.5 * r - 0.419 * g - 0.081 * b;
361
362Y1 = clamp (219 * y1 + 16);
363Cb = clamp (224 * pb + 128);
364Cr = clamp (224 * pr + 128);
365
366/* or shorter */
367
368y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;
369
370Y1 = clamp ( (219 / 255.0) * y1 + 16);
371Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128);
372Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128);
373 </programlisting>
374
375 <para>Inverse Transformation</para>
376
377 <programlisting>
378int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */
379int ER, EG, EB; /* output [0;255] */
380
381double r, g, b; /* temporaries */
382double y1, pb, pr;
383
384int
385clamp (double x)
386{
387 int r = x; /* round to nearest */
388
389 if (r < 0) return 0;
390 else if (r > 255) return 255;
391 else return r;
392}
393
394y1 = (255 / 219.0) * (Y1 - 16);
395pb = (255 / 224.0) * (Cb - 128);
396pr = (255 / 224.0) * (Cr - 128);
397
398r = 1.0 * y1 + 0 * pb + 1.402 * pr;
399g = 1.0 * y1 - 0.344 * pb - 0.714 * pr;
400b = 1.0 * y1 + 1.772 * pb + 0 * pr;
401
402ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
403EG = clamp (g * 255);
404EB = clamp (b * 255);
405 </programlisting>
406 </example>
407
408 <table pgwide="1" id="v4l2-colorspace" orient="land">
409 <title>enum v4l2_colorspace</title>
410 <tgroup cols="11" align="center">
411 <colspec align="left" />
412 <colspec align="center" />
413 <colspec align="left" />
414 <colspec colname="cr" />
415 <colspec colname="cg" />
416 <colspec colname="cb" />
417 <colspec colname="wp" />
418 <colspec colname="gc" />
419 <colspec colname="lum" />
420 <colspec colname="qy" />
421 <colspec colname="qc" />
422 <spanspec namest="cr" nameend="cb" spanname="chrom" />
423 <spanspec namest="qy" nameend="qc" spanname="quant" />
424 <spanspec namest="lum" nameend="qc" spanname="spam" />
425 <thead>
426 <row>
427 <entry morerows="1">Identifier</entry>
428 <entry morerows="1">Value</entry>
429 <entry morerows="1">Description</entry>
430 <entry spanname="chrom">Chromaticities<footnote>
431 <para>The coordinates of the color primaries are
432given in the CIE system (1931)</para>
433 </footnote></entry>
434 <entry morerows="1">White Point</entry>
435 <entry morerows="1">Gamma Correction</entry>
436 <entry morerows="1">Luminance E'<subscript>Y</subscript></entry>
437 <entry spanname="quant">Quantization</entry>
438 </row>
439 <row>
440 <entry>Red</entry>
441 <entry>Green</entry>
442 <entry>Blue</entry>
443 <entry>Y'</entry>
444 <entry>Cb, Cr</entry>
445 </row>
446 </thead>
447 <tbody valign="top">
448 <row>
449 <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry>
450 <entry>1</entry>
451 <entry>NTSC/PAL according to <xref linkend="smpte170m" />,
452<xref linkend="itu601" /></entry>
453 <entry>x = 0.630, y = 0.340</entry>
454 <entry>x = 0.310, y = 0.595</entry>
455 <entry>x = 0.155, y = 0.070</entry>
456 <entry>x = 0.3127, y = 0.3290,
457 Illuminant D<subscript>65</subscript></entry>
458 <entry>E' = 4.5 I for I ≤0.018,
4591.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry>
460 <entry>0.299 E'<subscript>R</subscript>
461+ 0.587 E'<subscript>G</subscript>
462+ 0.114 E'<subscript>B</subscript></entry>
463 <entry>219 E'<subscript>Y</subscript> + 16</entry>
464 <entry>224 P<subscript>B,R</subscript> + 128</entry>
465 </row>
466 <row>
467 <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry>
468 <entry>2</entry>
469 <entry>1125-Line (US) HDTV, see <xref
470linkend="smpte240m" /></entry>
471 <entry>x = 0.630, y = 0.340</entry>
472 <entry>x = 0.310, y = 0.595</entry>
473 <entry>x = 0.155, y = 0.070</entry>
474 <entry>x = 0.3127, y = 0.3290,
475 Illuminant D<subscript>65</subscript></entry>
476 <entry>E' = 4 I for I ≤0.0228,
4771.1115 I<superscript>0.45</superscript> - 0.1115 for 0.0228 < I</entry>
478 <entry>0.212 E'<subscript>R</subscript>
479+ 0.701 E'<subscript>G</subscript>
480+ 0.087 E'<subscript>B</subscript></entry>
481 <entry>219 E'<subscript>Y</subscript> + 16</entry>
482 <entry>224 P<subscript>B,R</subscript> + 128</entry>
483 </row>
484 <row>
485 <entry><constant>V4L2_COLORSPACE_REC709</constant></entry>
486 <entry>3</entry>
487 <entry>HDTV and modern devices, see <xref
488linkend="itu709" /></entry>
489 <entry>x = 0.640, y = 0.330</entry>
490 <entry>x = 0.300, y = 0.600</entry>
491 <entry>x = 0.150, y = 0.060</entry>
492 <entry>x = 0.3127, y = 0.3290,
493 Illuminant D<subscript>65</subscript></entry>
494 <entry>E' = 4.5 I for I ≤0.018,
4951.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry>
496 <entry>0.2125 E'<subscript>R</subscript>
497+ 0.7154 E'<subscript>G</subscript>
498+ 0.0721 E'<subscript>B</subscript></entry>
499 <entry>219 E'<subscript>Y</subscript> + 16</entry>
500 <entry>224 P<subscript>B,R</subscript> + 128</entry>
501 </row>
502 <row>
503 <entry><constant>V4L2_COLORSPACE_BT878</constant></entry>
504 <entry>4</entry>
505 <entry>Broken Bt878 extents<footnote>
506 <para>The ubiquitous Bt878 video capture chip
507quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range
508of Y' = 16 … 253, unlike Rec. 601 Y' = 16 …
509235. This is not a typo in the Bt878 documentation, it has been
510implemented in silicon. The chroma extents are unclear.</para>
511 </footnote>, <xref linkend="itu601" /></entry>
512 <entry>?</entry>
513 <entry>?</entry>
514 <entry>?</entry>
515 <entry>?</entry>
516 <entry>?</entry>
517 <entry>0.299 E'<subscript>R</subscript>
518+ 0.587 E'<subscript>G</subscript>
519+ 0.114 E'<subscript>B</subscript></entry>
520 <entry><emphasis>237</emphasis> E'<subscript>Y</subscript> + 16</entry>
521 <entry>224 P<subscript>B,R</subscript> + 128 (probably)</entry>
522 </row>
523 <row>
524 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry>
525 <entry>5</entry>
526 <entry>M/NTSC<footnote>
527 <para>No identifier exists for M/PAL which uses
528the chromaticities of M/NTSC, the remaining parameters are equal to B and
529G/PAL.</para>
530 </footnote> according to <xref linkend="itu470" />, <xref
531 linkend="itu601" /></entry>
532 <entry>x = 0.67, y = 0.33</entry>
533 <entry>x = 0.21, y = 0.71</entry>
534 <entry>x = 0.14, y = 0.08</entry>
535 <entry>x = 0.310, y = 0.316, Illuminant C</entry>
536 <entry>?</entry>
537 <entry>0.299 E'<subscript>R</subscript>
538+ 0.587 E'<subscript>G</subscript>
539+ 0.114 E'<subscript>B</subscript></entry>
540 <entry>219 E'<subscript>Y</subscript> + 16</entry>
541 <entry>224 P<subscript>B,R</subscript> + 128</entry>
542 </row>
543 <row>
544 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry>
545 <entry>6</entry>
546 <entry>625-line PAL and SECAM systems according to <xref
547linkend="itu470" />, <xref linkend="itu601" /></entry>
548 <entry>x = 0.64, y = 0.33</entry>
549 <entry>x = 0.29, y = 0.60</entry>
550 <entry>x = 0.15, y = 0.06</entry>
551 <entry>x = 0.313, y = 0.329,
552Illuminant D<subscript>65</subscript></entry>
553 <entry>?</entry>
554 <entry>0.299 E'<subscript>R</subscript>
555+ 0.587 E'<subscript>G</subscript>
556+ 0.114 E'<subscript>B</subscript></entry>
557 <entry>219 E'<subscript>Y</subscript> + 16</entry>
558 <entry>224 P<subscript>B,R</subscript> + 128</entry>
559 </row>
560 <row>
561 <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry>
562 <entry>7</entry>
563 <entry>JPEG Y'CbCr, see <xref linkend="jfif" />, <xref linkend="itu601" /></entry>
564 <entry>?</entry>
565 <entry>?</entry>
566 <entry>?</entry>
567 <entry>?</entry>
568 <entry>?</entry>
569 <entry>0.299 E'<subscript>R</subscript>
570+ 0.587 E'<subscript>G</subscript>
571+ 0.114 E'<subscript>B</subscript></entry>
572 <entry>256 E'<subscript>Y</subscript> + 16<footnote>
573 <para>Note JFIF quantizes
574Y'P<subscript>B</subscript>P<subscript>R</subscript> in range [0;+1] and
575[-0.5;+0.5] to <emphasis>257</emphasis> levels, however Y'CbCr signals
576are still clamped to [0;255].</para>
577 </footnote></entry>
578 <entry>256 P<subscript>B,R</subscript> + 128</entry>
579 </row>
580 <row>
581 <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry>
582 <entry>8</entry>
583 <entry>[?]</entry>
584 <entry>x = 0.640, y = 0.330</entry>
585 <entry>x = 0.300, y = 0.600</entry>
586 <entry>x = 0.150, y = 0.060</entry>
587 <entry>x = 0.3127, y = 0.3290,
588 Illuminant D<subscript>65</subscript></entry>
589 <entry>E' = 4.5 I for I ≤0.018,
5901.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry>
591 <entry spanname="spam">n/a</entry>
592 </row>
593 </tbody>
594 </tgroup>
595 </table>
596 </section>
597
598 <section id="pixfmt-indexed">
599 <title>Indexed Format</title>
600
601 <para>In this format each pixel is represented by an 8 bit index
602into a 256 entry ARGB palette. It is intended for <link
603linkend="osd">Video Output Overlays</link> only. There are no ioctls to
604access the palette, this must be done with ioctls of the Linux framebuffer API.</para>
605
606 <table pgwide="0" frame="none">
607 <title>Indexed Image Format</title>
608 <tgroup cols="37" align="center">
609 <colspec colname="id" align="left" />
610 <colspec colname="fourcc" />
611 <colspec colname="bit" />
612
613 <colspec colnum="4" colname="b07" align="center" />
614 <colspec colnum="5" colname="b06" align="center" />
615 <colspec colnum="6" colname="b05" align="center" />
616 <colspec colnum="7" colname="b04" align="center" />
617 <colspec colnum="8" colname="b03" align="center" />
618 <colspec colnum="9" colname="b02" align="center" />
619 <colspec colnum="10" colname="b01" align="center" />
620 <colspec colnum="11" colname="b00" align="center" />
621
622 <spanspec namest="b07" nameend="b00" spanname="b0" />
623 <spanspec namest="b17" nameend="b10" spanname="b1" />
624 <spanspec namest="b27" nameend="b20" spanname="b2" />
625 <spanspec namest="b37" nameend="b30" spanname="b3" />
626 <thead>
627 <row>
628 <entry>Identifier</entry>
629 <entry>Code</entry>
630 <entry> </entry>
631 <entry spanname="b0">Byte 0</entry>
632 </row>
633 <row>
634 <entry> </entry>
635 <entry> </entry>
636 <entry>Bit</entry>
637 <entry>7</entry>
638 <entry>6</entry>
639 <entry>5</entry>
640 <entry>4</entry>
641 <entry>3</entry>
642 <entry>2</entry>
643 <entry>1</entry>
644 <entry>0</entry>
645 </row>
646 </thead>
647 <tbody valign="top">
648 <row id="V4L2-PIX-FMT-PAL8">
649 <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry>
650 <entry>'PAL8'</entry>
651 <entry></entry>
652 <entry>i<subscript>7</subscript></entry>
653 <entry>i<subscript>6</subscript></entry>
654 <entry>i<subscript>5</subscript></entry>
655 <entry>i<subscript>4</subscript></entry>
656 <entry>i<subscript>3</subscript></entry>
657 <entry>i<subscript>2</subscript></entry>
658 <entry>i<subscript>1</subscript></entry>
659 <entry>i<subscript>0</subscript></entry>
660 </row>
661 </tbody>
662 </tgroup>
663 </table>
664 </section>
665
666 <section id="pixfmt-rgb">
667 <title>RGB Formats</title>
668
669 &sub-packed-rgb;
670 &sub-sbggr8;
671 &sub-sgbrg8;
672 &sub-sgrbg8;
673 &sub-srggb8;
674 &sub-sbggr16;
675 &sub-srggb10;
676 &sub-srggb10alaw8;
677 &sub-srggb10dpcm8;
678 &sub-srggb12;
679 </section>
680
681 <section id="yuv-formats">
682 <title>YUV Formats</title>
683
684 <para>YUV is the format native to TV broadcast and composite video
685signals. It separates the brightness information (Y) from the color
686information (U and V or Cb and Cr). The color information consists of
687red and blue <emphasis>color difference</emphasis> signals, this way
688the green component can be reconstructed by subtracting from the
689brightness component. See <xref linkend="colorspaces" /> for conversion
690examples. YUV was chosen because early television would only transmit
691brightness information. To add color in a way compatible with existing
692receivers a new signal carrier was added to transmit the color
693difference signals. Secondary in the YUV format the U and V components
694usually have lower resolution than the Y component. This is an analog
695video compression technique taking advantage of a property of the
696human visual system, being more sensitive to brightness
697information.</para>
698
699 &sub-packed-yuv;
700 &sub-grey;
701 &sub-y10;
702 &sub-y12;
703 &sub-y10b;
704 &sub-y16;
705 &sub-uv8;
706 &sub-yuyv;
707 &sub-uyvy;
708 &sub-yvyu;
709 &sub-vyuy;
710 &sub-y41p;
711 &sub-yuv420;
712 &sub-yuv420m;
713 &sub-yvu420m;
714 &sub-yuv410;
715 &sub-yuv422p;
716 &sub-yuv411p;
717 &sub-nv12;
718 &sub-nv12m;
719 &sub-nv12mt;
720 &sub-nv16;
721 &sub-nv24;
722 &sub-m420;
723 </section>
724
725 <section>
726 <title>Compressed Formats</title>
727
728 <table pgwide="1" frame="none" id="compressed-formats">
729 <title>Compressed Image Formats</title>
730 <tgroup cols="3" align="left">
731 &cs-def;
732 <thead>
733 <row>
734 <entry>Identifier</entry>
735 <entry>Code</entry>
736 <entry>Details</entry>
737 </row>
738 </thead>
739 <tbody valign="top">
740 <row id="V4L2-PIX-FMT-JPEG">
741 <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry>
742 <entry>'JPEG'</entry>
743 <entry>TBD. See also &VIDIOC-G-JPEGCOMP;,
744 &VIDIOC-S-JPEGCOMP;.</entry>
745 </row>
746 <row id="V4L2-PIX-FMT-MPEG">
747 <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry>
748 <entry>'MPEG'</entry>
749 <entry>MPEG multiplexed stream. The actual format is determined by
750extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
751<xref linkend="mpeg-control-id" />.</entry>
752 </row>
753 <row id="V4L2-PIX-FMT-H264">
754 <entry><constant>V4L2_PIX_FMT_H264</constant></entry>
755 <entry>'H264'</entry>
756 <entry>H264 video elementary stream with start codes.</entry>
757 </row>
758 <row id="V4L2-PIX-FMT-H264-NO-SC">
759 <entry><constant>V4L2_PIX_FMT_H264_NO_SC</constant></entry>
760 <entry>'AVC1'</entry>
761 <entry>H264 video elementary stream without start codes.</entry>
762 </row>
763 <row id="V4L2-PIX-FMT-H264-MVC">
764 <entry><constant>V4L2_PIX_FMT_H264_MVC</constant></entry>
765 <entry>'MVC'</entry>
766 <entry>H264 MVC video elementary stream.</entry>
767 </row>
768 <row id="V4L2-PIX-FMT-H263">
769 <entry><constant>V4L2_PIX_FMT_H263</constant></entry>
770 <entry>'H263'</entry>
771 <entry>H263 video elementary stream.</entry>
772 </row>
773 <row id="V4L2-PIX-FMT-MPEG1">
774 <entry><constant>V4L2_PIX_FMT_MPEG1</constant></entry>
775 <entry>'MPG1'</entry>
776 <entry>MPEG1 video elementary stream.</entry>
777 </row>
778 <row id="V4L2-PIX-FMT-MPEG2">
779 <entry><constant>V4L2_PIX_FMT_MPEG2</constant></entry>
780 <entry>'MPG2'</entry>
781 <entry>MPEG2 video elementary stream.</entry>
782 </row>
783 <row id="V4L2-PIX-FMT-MPEG4">
784 <entry><constant>V4L2_PIX_FMT_MPEG4</constant></entry>
785 <entry>'MPG4'</entry>
786 <entry>MPEG4 video elementary stream.</entry>
787 </row>
788 <row id="V4L2-PIX-FMT-XVID">
789 <entry><constant>V4L2_PIX_FMT_XVID</constant></entry>
790 <entry>'XVID'</entry>
791 <entry>Xvid video elementary stream.</entry>
792 </row>
793 <row id="V4L2-PIX-FMT-VC1-ANNEX-G">
794 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_G</constant></entry>
795 <entry>'VC1G'</entry>
796 <entry>VC1, SMPTE 421M Annex G compliant stream.</entry>
797 </row>
798 <row id="V4L2-PIX-FMT-VC1-ANNEX-L">
799 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_L</constant></entry>
800 <entry>'VC1L'</entry>
801 <entry>VC1, SMPTE 421M Annex L compliant stream.</entry>
802 </row>
803 <row id="V4L2-PIX-FMT-VP8">
804 <entry><constant>V4L2_PIX_FMT_VP8</constant></entry>
805 <entry>'VP8'</entry>
806 <entry>VP8 video elementary stream.</entry>
807 </row>
808 </tbody>
809 </tgroup>
810 </table>
811 </section>
812
813 <section id="pixfmt-reserved">
814 <title>Reserved Format Identifiers</title>
815
816 <para>These formats are not defined by this specification, they
817are just listed for reference and to avoid naming conflicts. If you
818want to register your own format, send an e-mail to the linux-media mailing
819list &v4l-ml; for inclusion in the <filename>videodev2.h</filename>
820file. If you want to share your format with other developers add a
821link to your documentation and send a copy to the linux-media mailing list
822for inclusion in this section. If you think your format should be listed
823in a standard format section please make a proposal on the linux-media mailing
824list.</para>
825
826 <table pgwide="1" frame="none" id="reserved-formats">
827 <title>Reserved Image Formats</title>
828 <tgroup cols="3" align="left">
829 &cs-def;
830 <thead>
831 <row>
832 <entry>Identifier</entry>
833 <entry>Code</entry>
834 <entry>Details</entry>
835 </row>
836 </thead>
837 <tbody valign="top">
838 <row id="V4L2-PIX-FMT-DV">
839 <entry><constant>V4L2_PIX_FMT_DV</constant></entry>
840 <entry>'dvsd'</entry>
841 <entry>unknown</entry>
842 </row>
843 <row id="V4L2-PIX-FMT-ET61X251">
844 <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry>
845 <entry>'E625'</entry>
846 <entry>Compressed format of the ET61X251 driver.</entry>
847 </row>
848 <row id="V4L2-PIX-FMT-HI240">
849 <entry><constant>V4L2_PIX_FMT_HI240</constant></entry>
850 <entry>'HI24'</entry>
851 <entry><para>8 bit RGB format used by the BTTV driver.</para></entry>
852 </row>
853 <row id="V4L2-PIX-FMT-HM12">
854 <entry><constant>V4L2_PIX_FMT_HM12</constant></entry>
855 <entry>'HM12'</entry>
856 <entry><para>YUV 4:2:0 format used by the
857IVTV driver, <ulink url="http://www.ivtvdriver.org/">
858http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the
859kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename>
860</para></entry>
861 </row>
862 <row id="V4L2-PIX-FMT-CPIA1">
863 <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry>
864 <entry>'CPIA'</entry>
865 <entry>YUV format used by the gspca cpia1 driver.</entry>
866 </row>
867 <row id="V4L2-PIX-FMT-JPGL">
868 <entry><constant>V4L2_PIX_FMT_JPGL</constant></entry>
869 <entry>'JPGL'</entry>
870 <entry>JPEG-Light format (Pegasus Lossless JPEG)
871 used in Divio webcams NW 80x.</entry>
872 </row>
873 <row id="V4L2-PIX-FMT-SPCA501">
874 <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry>
875 <entry>'S501'</entry>
876 <entry>YUYV per line used by the gspca driver.</entry>
877 </row>
878 <row id="V4L2-PIX-FMT-SPCA505">
879 <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry>
880 <entry>'S505'</entry>
881 <entry>YYUV per line used by the gspca driver.</entry>
882 </row>
883 <row id="V4L2-PIX-FMT-SPCA508">
884 <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry>
885 <entry>'S508'</entry>
886 <entry>YUVY per line used by the gspca driver.</entry>
887 </row>
888 <row id="V4L2-PIX-FMT-SPCA561">
889 <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry>
890 <entry>'S561'</entry>
891 <entry>Compressed GBRG Bayer format used by the gspca driver.</entry>
892 </row>
893 <row id="V4L2-PIX-FMT-PAC207">
894 <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry>
895 <entry>'P207'</entry>
896 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
897 </row>
898 <row id="V4L2-PIX-FMT-MR97310A">
899 <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry>
900 <entry>'M310'</entry>
901 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
902 </row>
903 <row id="V4L2-PIX-FMT-JL2005BCD">
904 <entry><constant>V4L2_PIX_FMT_JL2005BCD</constant></entry>
905 <entry>'JL20'</entry>
906 <entry>JPEG compressed RGGB Bayer format used by the gspca driver.</entry>
907 </row>
908 <row id="V4L2-PIX-FMT-OV511">
909 <entry><constant>V4L2_PIX_FMT_OV511</constant></entry>
910 <entry>'O511'</entry>
911 <entry>OV511 JPEG format used by the gspca driver.</entry>
912 </row>
913 <row id="V4L2-PIX-FMT-OV518">
914 <entry><constant>V4L2_PIX_FMT_OV518</constant></entry>
915 <entry>'O518'</entry>
916 <entry>OV518 JPEG format used by the gspca driver.</entry>
917 </row>
918 <row id="V4L2-PIX-FMT-PJPG">
919 <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry>
920 <entry>'PJPG'</entry>
921 <entry>Pixart 73xx JPEG format used by the gspca driver.</entry>
922 </row>
923 <row id="V4L2-PIX-FMT-SE401">
924 <entry><constant>V4L2_PIX_FMT_SE401</constant></entry>
925 <entry>'S401'</entry>
926 <entry>Compressed RGB format used by the gspca se401 driver</entry>
927 </row>
928 <row id="V4L2-PIX-FMT-SQ905C">
929 <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry>
930 <entry>'905C'</entry>
931 <entry>Compressed RGGB bayer format used by the gspca driver.</entry>
932 </row>
933 <row id="V4L2-PIX-FMT-MJPEG">
934 <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry>
935 <entry>'MJPG'</entry>
936 <entry>Compressed format used by the Zoran driver</entry>
937 </row>
938 <row id="V4L2-PIX-FMT-PWC1">
939 <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry>
940 <entry>'PWC1'</entry>
941 <entry>Compressed format of the PWC driver.</entry>
942 </row>
943 <row id="V4L2-PIX-FMT-PWC2">
944 <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry>
945 <entry>'PWC2'</entry>
946 <entry>Compressed format of the PWC driver.</entry>
947 </row>
948 <row id="V4L2-PIX-FMT-SN9C10X">
949 <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry>
950 <entry>'S910'</entry>
951 <entry>Compressed format of the SN9C102 driver.</entry>
952 </row>
953 <row id="V4L2-PIX-FMT-SN9C20X-I420">
954 <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry>
955 <entry>'S920'</entry>
956 <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry>
957 </row>
958 <row id="V4L2-PIX-FMT-SN9C2028">
959 <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry>
960 <entry>'SONX'</entry>
961 <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry>
962 </row>
963 <row id="V4L2-PIX-FMT-STV0680">
964 <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry>
965 <entry>'S680'</entry>
966 <entry>Bayer format of the gspca stv0680 driver.</entry>
967 </row>
968 <row id="V4L2-PIX-FMT-WNVA">
969 <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry>
970 <entry>'WNVA'</entry>
971 <entry><para>Used by the Winnov Videum driver, <ulink
972url="http://www.thedirks.org/winnov/">
973http://www.thedirks.org/winnov/</ulink></para></entry>
974 </row>
975 <row id="V4L2-PIX-FMT-TM6000">
976 <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry>
977 <entry>'TM60'</entry>
978 <entry><para>Used by Trident tm6000</para></entry>
979 </row>
980 <row id="V4L2-PIX-FMT-CIT-YYVYUY">
981 <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry>
982 <entry>'CITV'</entry>
983 <entry><para>Used by xirlink CIT, found at IBM webcams.</para>
984 <para>Uses one line of Y then 1 line of VYUY</para>
985 </entry>
986 </row>
987 <row id="V4L2-PIX-FMT-KONICA420">
988 <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry>
989 <entry>'KONI'</entry>
990 <entry><para>Used by Konica webcams.</para>
991 <para>YUV420 planar in blocks of 256 pixels.</para>
992 </entry>
993 </row>
994 <row id="V4L2-PIX-FMT-YYUV">
995 <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
996 <entry>'YYUV'</entry>
997 <entry>unknown</entry>
998 </row>
999 <row id="V4L2-PIX-FMT-Y4">
1000 <entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
1001 <entry>'Y04 '</entry>
1002 <entry>Old 4-bit greyscale format. Only the most significant 4 bits of each byte are used,
1003the other bits are set to 0.</entry>
1004 </row>
1005 <row id="V4L2-PIX-FMT-Y6">
1006 <entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
1007 <entry>'Y06 '</entry>
1008 <entry>Old 6-bit greyscale format. Only the most significant 6 bits of each byte are used,
1009the other bits are set to 0.</entry>
1010 </row>
1011 <row id="V4L2-PIX-FMT-S5C-UYVY-JPG">
1012 <entry><constant>V4L2_PIX_FMT_S5C_UYVY_JPG</constant></entry>
1013 <entry>'S5CI'</entry>
1014 <entry>Two-planar format used by Samsung S5C73MX cameras. The
1015first plane contains interleaved JPEG and UYVY image data, followed by meta data
1016in form of an array of offsets to the UYVY data blocks. The actual pointer array
1017follows immediately the interleaved JPEG/UYVY data, the number of entries in
1018this array equals the height of the UYVY image. Each entry is a 4-byte unsigned
1019integer in big endian order and it's an offset to a single pixel line of the
1020UYVY image. The first plane can start either with JPEG or UYVY data chunk. The
1021size of a single UYVY block equals the UYVY image's width multiplied by 2. The
1022size of a JPEG chunk depends on the image and can vary with each line.
1023<para>The second plane, at an offset of 4084 bytes, contains a 4-byte offset to
1024the pointer array in the first plane. This offset is followed by a 4-byte value
1025indicating size of the pointer array. All numbers in the second plane are also
1026in big endian order. Remaining data in the second plane is undefined. The
1027information in the second plane allows to easily find location of the pointer
1028array, which can be different for each frame. The size of the pointer array is
1029constant for given UYVY image height.</para>
1030<para>In order to extract UYVY and JPEG frames an application can initially set
1031a data pointer to the start of first plane and then add an offset from the first
1032entry of the pointers table. Such a pointer indicates start of an UYVY image
1033pixel line. Whole UYVY line can be copied to a separate buffer. These steps
1034should be repeated for each line, i.e. the number of entries in the pointer
1035array. Anything what's in between the UYVY lines is JPEG data and should be
1036concatenated to form the JPEG stream. </para>
1037</entry>
1038 </row>
1039 </tbody>
1040 </tgroup>
1041 </table>
1042 </section>