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1 <title>Image Formats</title>
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>
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
32 request an image size, drivers return the closest possible values. In
33 case of planar formats the <structfield>width</structfield> and
34 <structfield>height</structfield> applies to the largest plane. To
35 avoid ambiguities drivers must return values rounded up to a multiple
36 of the scale factor of any smaller planes. For example when the image
37 format 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
44 application. This is a little endian <link
45 linkend="v4l2-fourcc">four character code</link>. V4L2 defines
46 standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
47 linkend="yuv-formats" />, and reserved codes in <xref
48 linkend="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
54 can request to capture or output only the top or bottom field, or both
55 fields interlaced or sequentially stored in one buffer or alternating
56 in separate buffers. Drivers return the actual field order selected.
57 For 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
63 adjacent lines.</entry>
64 </row>
65 <row>
66 <entry spanname="hspan"><para>Both applications and drivers
67 can set this field to request padding bytes at the end of each line.
68 Drivers however may ignore the value requested by the application,
69 returning <structfield>width</structfield> times bytes per pixel or a
70 larger value required by the hardware. That implies applications can
71 just set this field to zero to get a reasonable
72 default.</para><para>Video hardware may access padding bytes,
73 therefore they must reside in accessible memory. Consider cases where
74 padding bytes after the last line of an image cross a system page
75 boundary. Input devices may write padding bytes, the value is
76 undefined. Output devices ignore the contents of padding
77 bytes.</para><para>When the image format is planar the
78 <structfield>bytesperline</structfield> value applies to the largest
79 plane and is divided by the same factor as the
80 <structfield>width</structfield> field for any smaller planes. For
81 example the Cb and Cr planes of a YUV 4:2:0 image have half as many
82 padding bytes following each line as the Y plane. To avoid ambiguities
83 drivers must return a <structfield>bytesperline</structfield> value
84 rounded 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,
90 set by the driver. Usually this is
91 <structfield>bytesperline</structfield> times
92 <structfield>height</structfield>. When the image consists of variable
93 length compressed data this is the maximum number of bytes required to
94 hold 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,
101 see <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
107 information about formats. When not used drivers and applications must
108 set this field to zero.</entry>
109 </row>
110 </tbody>
111 </tgroup>
112 </table>
113 </section>
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
168 codes 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>
206 <section>
207 <title>Standard Image Formats</title>
209 <para>In order to exchange images between drivers and
210 applications, it is necessary to have standard image data formats
211 which both sides will interpret the same way. V4L2 includes several
212 such formats, and this section is intended to be an unambiguous
213 specification of the standard image data formats in V4L2.</para>
215 <para>V4L2 drivers are not limited to these formats, however.
216 Driver-specific formats are possible. In that case the application may
217 depend on a codec to convert images to one of the standard formats
218 when needed. But the data can still be stored and retrieved in the
219 proprietary format. For example, a device may support a proprietary
220 compressed format. Applications can still capture and save the data in
221 the compressed format, saving much disk space, and later use a codec
222 to convert the images to the X Windows screen format when the video is
223 to be displayed.</para>
225 <para>Even so, ultimately, some standard formats are needed, so
226 the V4L2 specification would not be complete without well-defined
227 standard formats.</para>
229 <para>The V4L2 standard formats are mainly uncompressed formats. The
230 pixels are always arranged in memory from left to right, and from top
231 to bottom. The first byte of data in the image buffer is always for
232 the leftmost pixel of the topmost row. Following that is the pixel
233 immediately to its right, and so on until the end of the top row of
234 pixels. Following the rightmost pixel of the row there may be zero or
235 more bytes of padding to guarantee that each row of pixel data has a
236 certain alignment. Following the pad bytes, if any, is data for the
237 leftmost pixel of the second row from the top, and so on. The last row
238 has just as many pad bytes after it as the other rows.</para>
240 <para>In V4L2 each format has an identifier which looks like
241 <constant>PIX_FMT_XXX</constant>, defined in the <link
242 linkend="videodev">videodev.h</link> header file. These identifiers
243 represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link>
244 which are also listed below, however they are not the same as those
245 used in the Windows world.</para>
247 <para>For some formats, data is stored in separate, discontiguous
248 memory buffers. Those formats are identified by a separate set of FourCC codes
249 and are referred to as "multi-planar formats". For example, a YUV422 frame is
250 normally stored in one memory buffer, but it can also be placed in two or three
251 separate buffers, with Y component in one buffer and CbCr components in another
252 in the 2-planar version or with each component in its own buffer in the
253 3-planar case. Those sub-buffers are referred to as "planes".</para>
254 </section>
256 <section id="colorspaces">
257 <title>Colorspaces</title>
259 <para>[intro]</para>
261 <!-- See proposal by Billy Biggs, video4linux-list@redhat.com
262 on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and
263 http://vektor.theorem.ca/graphics/ycbcr/ and
264 http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html -->
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
279 signals</term>
280 <listitem>
281 <para>[to do]</para>
282 <para>E'<subscript>Y</subscript> =
283 Coeff<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
300 range [-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> =
304 K<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> =
309 K<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
326 stored in YUV images.</para>
327 </listitem>
328 </varlistentry>
329 </variablelist>
330 </para>
332 <example>
333 <title>ITU-R Rec. BT.601 color conversion</title>
335 <para>Forward Transformation</para>
337 <programlisting>
338 int ER, EG, EB; /* gamma corrected RGB input [0;255] */
339 int Y1, Cb, Cr; /* output [0;255] */
341 double r, g, b; /* temporaries */
342 double y1, pb, pr;
344 int
345 clamp (double x)
346 {
347 int r = x; /* round to nearest */
349 if (r < 0) return 0;
350 else if (r > 255) return 255;
351 else return r;
352 }
354 r = ER / 255.0;
355 g = EG / 255.0;
356 b = EB / 255.0;
358 y1 = 0.299 * r + 0.587 * g + 0.114 * b;
359 pb = -0.169 * r - 0.331 * g + 0.5 * b;
360 pr = 0.5 * r - 0.419 * g - 0.081 * b;
362 Y1 = clamp (219 * y1 + 16);
363 Cb = clamp (224 * pb + 128);
364 Cr = clamp (224 * pr + 128);
366 /* or shorter */
368 y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;
370 Y1 = clamp ( (219 / 255.0) * y1 + 16);
371 Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128);
372 Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128);
373 </programlisting>
375 <para>Inverse Transformation</para>
377 <programlisting>
378 int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */
379 int ER, EG, EB; /* output [0;255] */
381 double r, g, b; /* temporaries */
382 double y1, pb, pr;
384 int
385 clamp (double x)
386 {
387 int r = x; /* round to nearest */
389 if (r < 0) return 0;
390 else if (r > 255) return 255;
391 else return r;
392 }
394 y1 = (255 / 219.0) * (Y1 - 16);
395 pb = (255 / 224.0) * (Cb - 128);
396 pr = (255 / 224.0) * (Cr - 128);
398 r = 1.0 * y1 + 0 * pb + 1.402 * pr;
399 g = 1.0 * y1 - 0.344 * pb - 0.714 * pr;
400 b = 1.0 * y1 + 1.772 * pb + 0 * pr;
402 ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
403 EG = clamp (g * 255);
404 EB = clamp (b * 255);
405 </programlisting>
406 </example>
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
432 given 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,
459 1.099 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
470 linkend="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,
477 1.1115 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
488 linkend="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,
495 1.099 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
507 quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range
508 of Y' = 16 … 253, unlike Rec. 601 Y' = 16 …
509 235. This is not a typo in the Bt878 documentation, it has been
510 implemented 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
528 the chromaticities of M/NTSC, the remaining parameters are equal to B and
529 G/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
547 linkend="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,
552 Illuminant 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
574 Y'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
576 are 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,
590 1.099 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>
598 <section id="pixfmt-indexed">
599 <title>Indexed Format</title>
601 <para>In this format each pixel is represented by an 8 bit index
602 into a 256 entry ARGB palette. It is intended for <link
603 linkend="osd">Video Output Overlays</link> only. There are no ioctls to
604 access the palette, this must be done with ioctls of the Linux framebuffer API.</para>
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" />
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" />
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>
666 <section id="pixfmt-rgb">
667 <title>RGB Formats</title>
669 &sub-packed-rgb;
670 &sub-sbggr8;
671 &sub-sgbrg8;
672 &sub-sgrbg8;
673 &sub-srggb8;
674 &sub-sbggr16;
675 &sub-srggb10;
676 &sub-srggb12;
677 </section>
679 <section id="yuv-formats">
680 <title>YUV Formats</title>
682 <para>YUV is the format native to TV broadcast and composite video
683 signals. It separates the brightness information (Y) from the color
684 information (U and V or Cb and Cr). The color information consists of
685 red and blue <emphasis>color difference</emphasis> signals, this way
686 the green component can be reconstructed by subtracting from the
687 brightness component. See <xref linkend="colorspaces" /> for conversion
688 examples. YUV was chosen because early television would only transmit
689 brightness information. To add color in a way compatible with existing
690 receivers a new signal carrier was added to transmit the color
691 difference signals. Secondary in the YUV format the U and V components
692 usually have lower resolution than the Y component. This is an analog
693 video compression technique taking advantage of a property of the
694 human visual system, being more sensitive to brightness
695 information.</para>
697 &sub-packed-yuv;
698 &sub-grey;
699 &sub-y10;
700 &sub-y12;
701 &sub-y10b;
702 &sub-y16;
703 &sub-yuyv;
704 &sub-uyvy;
705 &sub-yvyu;
706 &sub-vyuy;
707 &sub-y41p;
708 &sub-yuv420;
709 &sub-yuv420m;
710 &sub-yuv410;
711 &sub-yuv422p;
712 &sub-yuv411p;
713 &sub-nv12;
714 &sub-nv12m;
715 &sub-nv12mt;
716 &sub-nv16;
717 &sub-m420;
718 </section>
720 <section>
721 <title>Compressed Formats</title>
723 <table pgwide="1" frame="none" id="compressed-formats">
724 <title>Compressed Image Formats</title>
725 <tgroup cols="3" align="left">
726 &cs-def;
727 <thead>
728 <row>
729 <entry>Identifier</entry>
730 <entry>Code</entry>
731 <entry>Details</entry>
732 </row>
733 </thead>
734 <tbody valign="top">
735 <row id="V4L2-PIX-FMT-JPEG">
736 <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry>
737 <entry>'JPEG'</entry>
738 <entry>TBD. See also &VIDIOC-G-JPEGCOMP;,
739 &VIDIOC-S-JPEGCOMP;.</entry>
740 </row>
741 <row id="V4L2-PIX-FMT-MPEG">
742 <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry>
743 <entry>'MPEG'</entry>
744 <entry>MPEG multiplexed stream. The actual format is determined by
745 extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
746 <xref linkend="mpeg-control-id" />.</entry>
747 </row>
748 <row id="V4L2-PIX-FMT-H264">
749 <entry><constant>V4L2_PIX_FMT_H264</constant></entry>
750 <entry>'H264'</entry>
751 <entry>H264 video elementary stream with start codes.</entry>
752 </row>
753 <row id="V4L2-PIX-FMT-H264-NO-SC">
754 <entry><constant>V4L2_PIX_FMT_H264_NO_SC</constant></entry>
755 <entry>'AVC1'</entry>
756 <entry>H264 video elementary stream without start codes.</entry>
757 </row>
758 <row id="V4L2-PIX-FMT-H263">
759 <entry><constant>V4L2_PIX_FMT_H263</constant></entry>
760 <entry>'H263'</entry>
761 <entry>H263 video elementary stream.</entry>
762 </row>
763 <row id="V4L2-PIX-FMT-MPEG1">
764 <entry><constant>V4L2_PIX_FMT_MPEG1</constant></entry>
765 <entry>'MPG1'</entry>
766 <entry>MPEG1 video elementary stream.</entry>
767 </row>
768 <row id="V4L2-PIX-FMT-MPEG2">
769 <entry><constant>V4L2_PIX_FMT_MPEG2</constant></entry>
770 <entry>'MPG2'</entry>
771 <entry>MPEG2 video elementary stream.</entry>
772 </row>
773 <row id="V4L2-PIX-FMT-MPEG4">
774 <entry><constant>V4L2_PIX_FMT_MPEG4</constant></entry>
775 <entry>'MPG4'</entry>
776 <entry>MPEG4 video elementary stream.</entry>
777 </row>
778 <row id="V4L2-PIX-FMT-XVID">
779 <entry><constant>V4L2_PIX_FMT_XVID</constant></entry>
780 <entry>'XVID'</entry>
781 <entry>Xvid video elementary stream.</entry>
782 </row>
783 <row id="V4L2-PIX-FMT-VC1-ANNEX-G">
784 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_G</constant></entry>
785 <entry>'VC1G'</entry>
786 <entry>VC1, SMPTE 421M Annex G compliant stream.</entry>
787 </row>
788 <row id="V4L2-PIX-FMT-VC1-ANNEX-L">
789 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_L</constant></entry>
790 <entry>'VC1L'</entry>
791 <entry>VC1, SMPTE 421M Annex L compliant stream.</entry>
792 </row>
793 </tbody>
794 </tgroup>
795 </table>
796 </section>
798 <section id="pixfmt-reserved">
799 <title>Reserved Format Identifiers</title>
801 <para>These formats are not defined by this specification, they
802 are just listed for reference and to avoid naming conflicts. If you
803 want to register your own format, send an e-mail to the linux-media mailing
804 list &v4l-ml; for inclusion in the <filename>videodev2.h</filename>
805 file. If you want to share your format with other developers add a
806 link to your documentation and send a copy to the linux-media mailing list
807 for inclusion in this section. If you think your format should be listed
808 in a standard format section please make a proposal on the linux-media mailing
809 list.</para>
811 <table pgwide="1" frame="none" id="reserved-formats">
812 <title>Reserved Image Formats</title>
813 <tgroup cols="3" align="left">
814 &cs-def;
815 <thead>
816 <row>
817 <entry>Identifier</entry>
818 <entry>Code</entry>
819 <entry>Details</entry>
820 </row>
821 </thead>
822 <tbody valign="top">
823 <row id="V4L2-PIX-FMT-DV">
824 <entry><constant>V4L2_PIX_FMT_DV</constant></entry>
825 <entry>'dvsd'</entry>
826 <entry>unknown</entry>
827 </row>
828 <row id="V4L2-PIX-FMT-ET61X251">
829 <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry>
830 <entry>'E625'</entry>
831 <entry>Compressed format of the ET61X251 driver.</entry>
832 </row>
833 <row id="V4L2-PIX-FMT-HI240">
834 <entry><constant>V4L2_PIX_FMT_HI240</constant></entry>
835 <entry>'HI24'</entry>
836 <entry><para>8 bit RGB format used by the BTTV driver.</para></entry>
837 </row>
838 <row id="V4L2-PIX-FMT-HM12">
839 <entry><constant>V4L2_PIX_FMT_HM12</constant></entry>
840 <entry>'HM12'</entry>
841 <entry><para>YUV 4:2:0 format used by the
842 IVTV driver, <ulink url="http://www.ivtvdriver.org/">
843 http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the
844 kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename>
845 </para></entry>
846 </row>
847 <row id="V4L2-PIX-FMT-CPIA1">
848 <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry>
849 <entry>'CPIA'</entry>
850 <entry>YUV format used by the gspca cpia1 driver.</entry>
851 </row>
852 <row id="V4L2-PIX-FMT-JPGL">
853 <entry><constant>V4L2_PIX_FMT_JPGL</constant></entry>
854 <entry>'JPGL'</entry>
855 <entry>JPEG-Light format (Pegasus Lossless JPEG)
856 used in Divio webcams NW 80x.</entry>
857 </row>
858 <row id="V4L2-PIX-FMT-SPCA501">
859 <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry>
860 <entry>'S501'</entry>
861 <entry>YUYV per line used by the gspca driver.</entry>
862 </row>
863 <row id="V4L2-PIX-FMT-SPCA505">
864 <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry>
865 <entry>'S505'</entry>
866 <entry>YYUV per line used by the gspca driver.</entry>
867 </row>
868 <row id="V4L2-PIX-FMT-SPCA508">
869 <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry>
870 <entry>'S508'</entry>
871 <entry>YUVY per line used by the gspca driver.</entry>
872 </row>
873 <row id="V4L2-PIX-FMT-SPCA561">
874 <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry>
875 <entry>'S561'</entry>
876 <entry>Compressed GBRG Bayer format used by the gspca driver.</entry>
877 </row>
878 <row id="V4L2-PIX-FMT-SGRBG10DPCM8">
879 <entry><constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant></entry>
880 <entry>'DB10'</entry>
881 <entry>10 bit raw Bayer DPCM compressed to 8 bits.</entry>
882 </row>
883 <row id="V4L2-PIX-FMT-PAC207">
884 <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry>
885 <entry>'P207'</entry>
886 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
887 </row>
888 <row id="V4L2-PIX-FMT-MR97310A">
889 <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry>
890 <entry>'M310'</entry>
891 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
892 </row>
893 <row id="V4L2-PIX-FMT-OV511">
894 <entry><constant>V4L2_PIX_FMT_OV511</constant></entry>
895 <entry>'O511'</entry>
896 <entry>OV511 JPEG format used by the gspca driver.</entry>
897 </row>
898 <row id="V4L2-PIX-FMT-OV518">
899 <entry><constant>V4L2_PIX_FMT_OV518</constant></entry>
900 <entry>'O518'</entry>
901 <entry>OV518 JPEG format used by the gspca driver.</entry>
902 </row>
903 <row id="V4L2-PIX-FMT-PJPG">
904 <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry>
905 <entry>'PJPG'</entry>
906 <entry>Pixart 73xx JPEG format used by the gspca driver.</entry>
907 </row>
908 <row id="V4L2-PIX-FMT-SE401">
909 <entry><constant>V4L2_PIX_FMT_SE401</constant></entry>
910 <entry>'S401'</entry>
911 <entry>Compressed RGB format used by the gspca se401 driver</entry>
912 </row>
913 <row id="V4L2-PIX-FMT-SQ905C">
914 <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry>
915 <entry>'905C'</entry>
916 <entry>Compressed RGGB bayer format used by the gspca driver.</entry>
917 </row>
918 <row id="V4L2-PIX-FMT-MJPEG">
919 <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry>
920 <entry>'MJPG'</entry>
921 <entry>Compressed format used by the Zoran driver</entry>
922 </row>
923 <row id="V4L2-PIX-FMT-PWC1">
924 <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry>
925 <entry>'PWC1'</entry>
926 <entry>Compressed format of the PWC driver.</entry>
927 </row>
928 <row id="V4L2-PIX-FMT-PWC2">
929 <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry>
930 <entry>'PWC2'</entry>
931 <entry>Compressed format of the PWC driver.</entry>
932 </row>
933 <row id="V4L2-PIX-FMT-SN9C10X">
934 <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry>
935 <entry>'S910'</entry>
936 <entry>Compressed format of the SN9C102 driver.</entry>
937 </row>
938 <row id="V4L2-PIX-FMT-SN9C20X-I420">
939 <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry>
940 <entry>'S920'</entry>
941 <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry>
942 </row>
943 <row id="V4L2-PIX-FMT-SN9C2028">
944 <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry>
945 <entry>'SONX'</entry>
946 <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry>
947 </row>
948 <row id="V4L2-PIX-FMT-STV0680">
949 <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry>
950 <entry>'S680'</entry>
951 <entry>Bayer format of the gspca stv0680 driver.</entry>
952 </row>
953 <row id="V4L2-PIX-FMT-WNVA">
954 <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry>
955 <entry>'WNVA'</entry>
956 <entry><para>Used by the Winnov Videum driver, <ulink
957 url="http://www.thedirks.org/winnov/">
958 http://www.thedirks.org/winnov/</ulink></para></entry>
959 </row>
960 <row id="V4L2-PIX-FMT-TM6000">
961 <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry>
962 <entry>'TM60'</entry>
963 <entry><para>Used by Trident tm6000</para></entry>
964 </row>
965 <row id="V4L2-PIX-FMT-CIT-YYVYUY">
966 <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry>
967 <entry>'CITV'</entry>
968 <entry><para>Used by xirlink CIT, found at IBM webcams.</para>
969 <para>Uses one line of Y then 1 line of VYUY</para>
970 </entry>
971 </row>
972 <row id="V4L2-PIX-FMT-KONICA420">
973 <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry>
974 <entry>'KONI'</entry>
975 <entry><para>Used by Konica webcams.</para>
976 <para>YUV420 planar in blocks of 256 pixels.</para>
977 </entry>
978 </row>
979 <row id="V4L2-PIX-FMT-YYUV">
980 <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
981 <entry>'YYUV'</entry>
982 <entry>unknown</entry>
983 </row>
984 <row id="V4L2-PIX-FMT-Y4">
985 <entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
986 <entry>'Y04 '</entry>
987 <entry>Old 4-bit greyscale format. Only the least significant 4 bits of each byte are used,
988 the other bits are set to 0.</entry>
989 </row>
990 <row id="V4L2-PIX-FMT-Y6">
991 <entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
992 <entry>'Y06 '</entry>
993 <entry>Old 6-bit greyscale format. Only the least significant 6 bits of each byte are used,
994 the other bits are set to 0.</entry>
995 </row>
996 </tbody>
997 </tgroup>
998 </table>
999 </section>
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