Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 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 first 84 plane and is divided by the same factor as the 85 <structfield>width</structfield> field for the other 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 <row> 161 <entry>&v4l2-xfer-func;</entry> 162 <entry><structfield>xfer_func</structfield></entry> 163 <entry>This information supplements the 164 <structfield>colorspace</structfield> and must be set by the driver for 165 capture streams and by the application for output streams, 166 see <xref linkend="colorspaces" />.</entry> 167 </row> 168 </tbody> 169 </tgroup> 170 </table> 171 </section> 172 173 <section> 174 <title>Multi-planar format structures</title> 175 <para>The <structname>v4l2_plane_pix_format</structname> structures define 176 size and layout for each of the planes in a multi-planar format. 177 The <structname>v4l2_pix_format_mplane</structname> structure contains 178 information common to all planes (such as image width and height) and 179 an array of <structname>v4l2_plane_pix_format</structname> structures, 180 describing all planes of that format.</para> 181 <table pgwide="1" frame="none" id="v4l2-plane-pix-format"> 182 <title>struct <structname>v4l2_plane_pix_format</structname></title> 183 <tgroup cols="3"> 184 &cs-str; 185 <tbody valign="top"> 186 <row> 187 <entry>__u32</entry> 188 <entry><structfield>sizeimage</structfield></entry> 189 <entry>Maximum size in bytes required for image data in this plane. 190 </entry> 191 </row> 192 <row> 193 <entry>__u32</entry> 194 <entry><structfield>bytesperline</structfield></entry> 195 <entry>Distance in bytes between the leftmost pixels in two adjacent 196 lines. See &v4l2-pix-format;.</entry> 197 </row> 198 <row> 199 <entry>__u16</entry> 200 <entry><structfield>reserved[6]</structfield></entry> 201 <entry>Reserved for future extensions. Should be zeroed by drivers and 202 applications.</entry> 203 </row> 204 </tbody> 205 </tgroup> 206 </table> 207 <table pgwide="1" frame="none" id="v4l2-pix-format-mplane"> 208 <title>struct <structname>v4l2_pix_format_mplane</structname></title> 209 <tgroup cols="3"> 210 &cs-str; 211 <tbody valign="top"> 212 <row> 213 <entry>__u32</entry> 214 <entry><structfield>width</structfield></entry> 215 <entry>Image width in pixels. See &v4l2-pix-format;.</entry> 216 </row> 217 <row> 218 <entry>__u32</entry> 219 <entry><structfield>height</structfield></entry> 220 <entry>Image height in pixels. See &v4l2-pix-format;.</entry> 221 </row> 222 <row> 223 <entry>__u32</entry> 224 <entry><structfield>pixelformat</structfield></entry> 225 <entry>The pixel format. Both single- and multi-planar four character 226 codes can be used.</entry> 227 </row> 228 <row> 229 <entry>&v4l2-field;</entry> 230 <entry><structfield>field</structfield></entry> 231 <entry>See &v4l2-pix-format;.</entry> 232 </row> 233 <row> 234 <entry>&v4l2-colorspace;</entry> 235 <entry><structfield>colorspace</structfield></entry> 236 <entry>See &v4l2-pix-format;.</entry> 237 </row> 238 <row> 239 <entry>&v4l2-plane-pix-format;</entry> 240 <entry><structfield>plane_fmt[VIDEO_MAX_PLANES]</structfield></entry> 241 <entry>An array of structures describing format of each plane this 242 pixel format consists of. The number of valid entries in this array 243 has to be put in the <structfield>num_planes</structfield> 244 field.</entry> 245 </row> 246 <row> 247 <entry>__u8</entry> 248 <entry><structfield>num_planes</structfield></entry> 249 <entry>Number of planes (i.e. separate memory buffers) for this format 250 and the number of valid entries in the 251 <structfield>plane_fmt</structfield> array.</entry> 252 </row> 253 <row> 254 <entry>__u8</entry> 255 <entry><structfield>flags</structfield></entry> 256 <entry>Flags set by the application or driver, see <xref 257 linkend="format-flags" />.</entry> 258 </row> 259 <row> 260 <entry>&v4l2-ycbcr-encoding;</entry> 261 <entry><structfield>ycbcr_enc</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>&v4l2-quantization;</entry> 269 <entry><structfield>quantization</structfield></entry> 270 <entry>This information supplements the 271 <structfield>colorspace</structfield> and must be set by the driver for 272 capture streams and by the application for output streams, 273 see <xref linkend="colorspaces" />.</entry> 274 </row> 275 <row> 276 <entry>&v4l2-xfer-func;</entry> 277 <entry><structfield>xfer_func</structfield></entry> 278 <entry>This information supplements the 279 <structfield>colorspace</structfield> and must be set by the driver for 280 capture streams and by the application for output streams, 281 see <xref linkend="colorspaces" />.</entry> 282 </row> 283 <row> 284 <entry>__u8</entry> 285 <entry><structfield>reserved[7]</structfield></entry> 286 <entry>Reserved for future extensions. Should be zeroed by drivers 287 and applications.</entry> 288 </row> 289 </tbody> 290 </tgroup> 291 </table> 292 </section> 293 294 <section> 295 <title>Standard Image Formats</title> 296 297 <para>In order to exchange images between drivers and 298 applications, it is necessary to have standard image data formats 299 which both sides will interpret the same way. V4L2 includes several 300 such formats, and this section is intended to be an unambiguous 301 specification of the standard image data formats in V4L2.</para> 302 303 <para>V4L2 drivers are not limited to these formats, however. 304 Driver-specific formats are possible. In that case the application may 305 depend on a codec to convert images to one of the standard formats 306 when needed. But the data can still be stored and retrieved in the 307 proprietary format. For example, a device may support a proprietary 308 compressed format. Applications can still capture and save the data in 309 the compressed format, saving much disk space, and later use a codec 310 to convert the images to the X Windows screen format when the video is 311 to be displayed.</para> 312 313 <para>Even so, ultimately, some standard formats are needed, so 314 the V4L2 specification would not be complete without well-defined 315 standard formats.</para> 316 317 <para>The V4L2 standard formats are mainly uncompressed formats. The 318 pixels are always arranged in memory from left to right, and from top 319 to bottom. The first byte of data in the image buffer is always for 320 the leftmost pixel of the topmost row. Following that is the pixel 321 immediately to its right, and so on until the end of the top row of 322 pixels. Following the rightmost pixel of the row there may be zero or 323 more bytes of padding to guarantee that each row of pixel data has a 324 certain alignment. Following the pad bytes, if any, is data for the 325 leftmost pixel of the second row from the top, and so on. The last row 326 has just as many pad bytes after it as the other rows.</para> 327 328 <para>In V4L2 each format has an identifier which looks like 329 <constant>PIX_FMT_XXX</constant>, defined in the <link 330 linkend="videodev">videodev2.h</link> header file. These identifiers 331 represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link> 332 which are also listed below, however they are not the same as those 333 used in the Windows world.</para> 334 335 <para>For some formats, data is stored in separate, discontiguous 336 memory buffers. Those formats are identified by a separate set of FourCC codes 337 and are referred to as "multi-planar formats". For example, a YUV422 frame is 338 normally stored in one memory buffer, but it can also be placed in two or three 339 separate buffers, with Y component in one buffer and CbCr components in another 340 in the 2-planar version or with each component in its own buffer in the 341 3-planar case. Those sub-buffers are referred to as "planes".</para> 342 </section> 343 344 <section id="colorspaces"> 345 <title>Colorspaces</title> 346 347 <para>'Color' is a very complex concept and depends on physics, chemistry and 348 biology. Just because you have three numbers that describe the 'red', 'green' 349 and 'blue' components of the color of a pixel does not mean that you can accurately 350 display that color. A colorspace defines what it actually <emphasis>means</emphasis> 351 to have an RGB value of e.g. (255, 0, 0). That is, which color should be 352 reproduced on the screen in a perfectly calibrated environment.</para> 353 354 <para>In order to do that we first need to have a good definition of 355 color, i.e. some way to uniquely and unambiguously define a color so that someone 356 else can reproduce it. Human color vision is trichromatic since the human eye has 357 color receptors that are sensitive to three different wavelengths of light. Hence 358 the need to use three numbers to describe color. Be glad you are not a mantis shrimp 359 as those are sensitive to 12 different wavelengths, so instead of RGB we would be 360 using the ABCDEFGHIJKL colorspace...</para> 361 362 <para>Color exists only in the eye and brain and is the result of how strongly 363 color receptors are stimulated. This is based on the Spectral 364 Power Distribution (SPD) which is a graph showing the intensity (radiant power) 365 of the light at wavelengths covering the visible spectrum as it enters the eye. 366 The science of colorimetry is about the relationship between the SPD and color as 367 perceived by the human brain.</para> 368 369 <para>Since the human eye has only three color receptors it is perfectly 370 possible that different SPDs will result in the same stimulation of those receptors 371 and are perceived as the same color, even though the SPD of the light is 372 different.</para> 373 374 <para>In the 1920s experiments were devised to determine the relationship 375 between SPDs and the perceived color and that resulted in the CIE 1931 standard 376 that defines spectral weighting functions that model the perception of color. 377 Specifically that standard defines functions that can take an SPD and calculate 378 the stimulus for each color receptor. After some further mathematical transforms 379 these stimuli are known as the <emphasis>CIE XYZ tristimulus</emphasis> values 380 and these X, Y and Z values describe a color as perceived by a human unambiguously. 381 These X, Y and Z values are all in the range [0…1].</para> 382 383 <para>The Y value in the CIE XYZ colorspace corresponds to luminance. Often 384 the CIE XYZ colorspace is transformed to the normalized CIE xyY colorspace:</para> 385 386 <para>x = X / (X + Y + Z)</para> 387 <para>y = Y / (X + Y + Z)</para> 388 389 <para>The x and y values are the chromaticity coordinates and can be used to 390 define a color without the luminance component Y. It is very confusing to 391 have such similar names for these colorspaces. Just be aware that if colors 392 are specified with lower case 'x' and 'y', then the CIE xyY colorspace is 393 used. Upper case 'X' and 'Y' refer to the CIE XYZ colorspace. Also, y has nothing 394 to do with luminance. Together x and y specify a color, and Y the luminance. 395 That is really all you need to remember from a practical point of view. At 396 the end of this section you will find reading resources that go into much more 397 detail if you are interested. 398 </para> 399 400 <para>A monitor or TV will reproduce colors by emitting light at three 401 different wavelengths, the combination of which will stimulate the color receptors 402 in the eye and thus cause the perception of color. Historically these wavelengths 403 were defined by the red, green and blue phosphors used in the displays. These 404 <emphasis>color primaries</emphasis> are part of what defines a colorspace.</para> 405 406 <para>Different display devices will have different primaries and some 407 primaries are more suitable for some display technologies than others. This has 408 resulted in a variety of colorspaces that are used for different display 409 technologies or uses. To define a colorspace you need to define the three 410 color primaries (these are typically defined as x, y chromaticity coordinates 411 from the CIE xyY colorspace) but also the white reference: that is the color obtained 412 when all three primaries are at maximum power. This determines the relative power 413 or energy of the primaries. This is usually chosen to be close to daylight which has 414 been defined as the CIE D65 Illuminant.</para> 415 416 <para>To recapitulate: the CIE XYZ colorspace uniquely identifies colors. 417 Other colorspaces are defined by three chromaticity coordinates defined in the 418 CIE xyY colorspace. Based on those a 3x3 matrix can be constructed that 419 transforms CIE XYZ colors to colors in the new colorspace. 420 </para> 421 422 <para>Both the CIE XYZ and the RGB colorspace that are derived from the 423 specific chromaticity primaries are linear colorspaces. But neither the eye, 424 nor display technology is linear. Doubling the values of all components in 425 the linear colorspace will not be perceived as twice the intensity of the color. 426 So each colorspace also defines a transfer function that takes a linear color 427 component value and transforms it to the non-linear component value, which is a 428 closer match to the non-linear performance of both the eye and displays. Linear 429 component values are denoted RGB, non-linear are denoted as R'G'B'. In general 430 colors used in graphics are all R'G'B', except in openGL which uses linear RGB. 431 Special care should be taken when dealing with openGL to provide linear RGB colors 432 or to use the built-in openGL support to apply the inverse transfer function.</para> 433 434 <para>The final piece that defines a colorspace is a function that 435 transforms non-linear R'G'B' to non-linear Y'CbCr. This function is determined 436 by the so-called luma coefficients. There may be multiple possible Y'CbCr 437 encodings allowed for the same colorspace. Many encodings of color 438 prefer to use luma (Y') and chroma (CbCr) instead of R'G'B'. Since the human 439 eye is more sensitive to differences in luminance than in color this encoding 440 allows one to reduce the amount of color information compared to the luma 441 data. Note that the luma (Y') is unrelated to the Y in the CIE XYZ colorspace. 442 Also note that Y'CbCr is often called YCbCr or YUV even though these are 443 strictly speaking wrong.</para> 444 445 <para>Sometimes people confuse Y'CbCr as being a colorspace. This is not 446 correct, it is just an encoding of an R'G'B' color into luma and chroma 447 values. The underlying colorspace that is associated with the R'G'B' color 448 is also associated with the Y'CbCr color.</para> 449 450 <para>The final step is how the RGB, R'G'B' or Y'CbCr values are 451 quantized. The CIE XYZ colorspace where X, Y and Z are in the range 452 [0…1] describes all colors that humans can perceive, but the transform to 453 another colorspace will produce colors that are outside the [0…1] range. 454 Once clamped to the [0…1] range those colors can no longer be reproduced 455 in that colorspace. This clamping is what reduces the extent or gamut of the 456 colorspace. How the range of [0…1] is translated to integer values in the 457 range of [0…255] (or higher, depending on the color depth) is called the 458 quantization. This is <emphasis>not</emphasis> part of the colorspace 459 definition. In practice RGB or R'G'B' values are full range, i.e. they 460 use the full [0…255] range. Y'CbCr values on the other hand are limited 461 range with Y' using [16…235] and Cb and Cr using [16…240].</para> 462 463 <para>Unfortunately, in some cases limited range RGB is also used 464 where the components use the range [16…235]. And full range Y'CbCr also exists 465 using the [0…255] range.</para> 466 467 <para>In order to correctly interpret a color you need to know the 468 quantization range, whether it is R'G'B' or Y'CbCr, the used Y'CbCr encoding 469 and the colorspace. 470 From that information you can calculate the corresponding CIE XYZ color 471 and map that again to whatever colorspace your display device uses.</para> 472 473 <para>The colorspace definition itself consists of the three 474 chromaticity primaries, the white reference chromaticity, a transfer 475 function and the luma coefficients needed to transform R'G'B' to Y'CbCr. While 476 some colorspace standards correctly define all four, quite often the colorspace 477 standard only defines some, and you have to rely on other standards for 478 the missing pieces. The fact that colorspaces are often a mix of different 479 standards also led to very confusing naming conventions where the name of 480 a standard was used to name a colorspace when in fact that standard was 481 part of various other colorspaces as well.</para> 482 483 <para>If you want to read more about colors and colorspaces, then the 484 following resources are useful: <xref linkend="poynton" /> is a good practical 485 book for video engineers, <xref linkend="colimg" /> has a much broader scope and 486 describes many more aspects of color (physics, chemistry, biology, etc.). 487 The <ulink url="http://www.brucelindbloom.com">http://www.brucelindbloom.com</ulink> 488 website is an excellent resource, especially with respect to the mathematics behind 489 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 490 is also very useful.</para> 491 </section> 492 493 <section> 494 <title>Defining Colorspaces in V4L2</title> 495 <para>In V4L2 colorspaces are defined by four values. The first is the colorspace 496 identifier (&v4l2-colorspace;) which defines the chromaticities, the default transfer 497 function, the default Y'CbCr encoding and the default quantization method. The second 498 is the transfer function identifier (&v4l2-xfer-func;) to specify non-standard 499 transfer functions. The third is the Y'CbCr encoding identifier (&v4l2-ycbcr-encoding;) 500 to specify non-standard Y'CbCr encodings and the fourth is the quantization identifier 501 (&v4l2-quantization;) to specify non-standard quantization methods. Most of the time 502 only the colorspace field of &v4l2-pix-format; or &v4l2-pix-format-mplane; needs to 503 be filled in. Note that the default R'G'B' quantization is full range for all 504 colorspaces except for BT.2020 which uses limited range R'G'B' quantization.</para> 505 506 <table pgwide="1" frame="none" id="v4l2-colorspace"> 507 <title>V4L2 Colorspaces</title> 508 <tgroup cols="2" align="left"> 509 &cs-def; 510 <thead> 511 <row> 512 <entry>Identifier</entry> 513 <entry>Details</entry> 514 </row> 515 </thead> 516 <tbody valign="top"> 517 <row> 518 <entry><constant>V4L2_COLORSPACE_DEFAULT</constant></entry> 519 <entry>The default colorspace. This can be used by applications to let the 520 driver fill in the colorspace.</entry> 521 </row> 522 <row> 523 <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry> 524 <entry>See <xref linkend="col-smpte-170m" />.</entry> 525 </row> 526 <row> 527 <entry><constant>V4L2_COLORSPACE_REC709</constant></entry> 528 <entry>See <xref linkend="col-rec709" />.</entry> 529 </row> 530 <row> 531 <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry> 532 <entry>See <xref linkend="col-srgb" />.</entry> 533 </row> 534 <row> 535 <entry><constant>V4L2_COLORSPACE_ADOBERGB</constant></entry> 536 <entry>See <xref linkend="col-adobergb" />.</entry> 537 </row> 538 <row> 539 <entry><constant>V4L2_COLORSPACE_BT2020</constant></entry> 540 <entry>See <xref linkend="col-bt2020" />.</entry> 541 </row> 542 <row> 543 <entry><constant>V4L2_COLORSPACE_DCI_P3</constant></entry> 544 <entry>See <xref linkend="col-dcip3" />.</entry> 545 </row> 546 <row> 547 <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry> 548 <entry>See <xref linkend="col-smpte-240m" />.</entry> 549 </row> 550 <row> 551 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry> 552 <entry>See <xref linkend="col-sysm" />.</entry> 553 </row> 554 <row> 555 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry> 556 <entry>See <xref linkend="col-sysbg" />.</entry> 557 </row> 558 <row> 559 <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry> 560 <entry>See <xref linkend="col-jpeg" />.</entry> 561 </row> 562 <row> 563 <entry><constant>V4L2_COLORSPACE_RAW</constant></entry> 564 <entry>The raw colorspace. This is used for raw image capture where 565 the image is minimally processed and is using the internal colorspace 566 of the device. The software that processes an image using this 567 'colorspace' will have to know the internals of the capture device.</entry> 568 </row> 569 </tbody> 570 </tgroup> 571 </table> 572 573 <table pgwide="1" frame="none" id="v4l2-xfer-func"> 574 <title>V4L2 Transfer Function</title> 575 <tgroup cols="2" align="left"> 576 &cs-def; 577 <thead> 578 <row> 579 <entry>Identifier</entry> 580 <entry>Details</entry> 581 </row> 582 </thead> 583 <tbody valign="top"> 584 <row> 585 <entry><constant>V4L2_XFER_FUNC_DEFAULT</constant></entry> 586 <entry>Use the default transfer function as defined by the colorspace.</entry> 587 </row> 588 <row> 589 <entry><constant>V4L2_XFER_FUNC_709</constant></entry> 590 <entry>Use the Rec. 709 transfer function.</entry> 591 </row> 592 <row> 593 <entry><constant>V4L2_XFER_FUNC_SRGB</constant></entry> 594 <entry>Use the sRGB transfer function.</entry> 595 </row> 596 <row> 597 <entry><constant>V4L2_XFER_FUNC_ADOBERGB</constant></entry> 598 <entry>Use the AdobeRGB transfer function.</entry> 599 </row> 600 <row> 601 <entry><constant>V4L2_XFER_FUNC_SMPTE240M</constant></entry> 602 <entry>Use the SMPTE 240M transfer function.</entry> 603 </row> 604 <row> 605 <entry><constant>V4L2_XFER_FUNC_NONE</constant></entry> 606 <entry>Do not use a transfer function (i.e. use linear RGB values).</entry> 607 </row> 608 <row> 609 <entry><constant>V4L2_XFER_FUNC_DCI_P3</constant></entry> 610 <entry>Use the DCI-P3 transfer function.</entry> 611 </row> 612 <row> 613 <entry><constant>V4L2_XFER_FUNC_SMPTE2084</constant></entry> 614 <entry>Use the SMPTE 2084 transfer function.</entry> 615 </row> 616 </tbody> 617 </tgroup> 618 </table> 619 620 <table pgwide="1" frame="none" id="v4l2-ycbcr-encoding"> 621 <title>V4L2 Y'CbCr Encodings</title> 622 <tgroup cols="2" align="left"> 623 &cs-def; 624 <thead> 625 <row> 626 <entry>Identifier</entry> 627 <entry>Details</entry> 628 </row> 629 </thead> 630 <tbody valign="top"> 631 <row> 632 <entry><constant>V4L2_YCBCR_ENC_DEFAULT</constant></entry> 633 <entry>Use the default Y'CbCr encoding as defined by the colorspace.</entry> 634 </row> 635 <row> 636 <entry><constant>V4L2_YCBCR_ENC_601</constant></entry> 637 <entry>Use the BT.601 Y'CbCr encoding.</entry> 638 </row> 639 <row> 640 <entry><constant>V4L2_YCBCR_ENC_709</constant></entry> 641 <entry>Use the Rec. 709 Y'CbCr encoding.</entry> 642 </row> 643 <row> 644 <entry><constant>V4L2_YCBCR_ENC_XV601</constant></entry> 645 <entry>Use the extended gamut xvYCC BT.601 encoding.</entry> 646 </row> 647 <row> 648 <entry><constant>V4L2_YCBCR_ENC_XV709</constant></entry> 649 <entry>Use the extended gamut xvYCC Rec. 709 encoding.</entry> 650 </row> 651 <row> 652 <entry><constant>V4L2_YCBCR_ENC_SYCC</constant></entry> 653 <entry>Use the extended gamut sYCC encoding.</entry> 654 </row> 655 <row> 656 <entry><constant>V4L2_YCBCR_ENC_BT2020</constant></entry> 657 <entry>Use the default non-constant luminance BT.2020 Y'CbCr encoding.</entry> 658 </row> 659 <row> 660 <entry><constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant></entry> 661 <entry>Use the constant luminance BT.2020 Yc'CbcCrc encoding.</entry> 662 </row> 663 </tbody> 664 </tgroup> 665 </table> 666 667 <table pgwide="1" frame="none" id="v4l2-quantization"> 668 <title>V4L2 Quantization Methods</title> 669 <tgroup cols="2" align="left"> 670 &cs-def; 671 <thead> 672 <row> 673 <entry>Identifier</entry> 674 <entry>Details</entry> 675 </row> 676 </thead> 677 <tbody valign="top"> 678 <row> 679 <entry><constant>V4L2_QUANTIZATION_DEFAULT</constant></entry> 680 <entry>Use the default quantization encoding as defined by the colorspace. 681 This is always full range for R'G'B' (except for the BT.2020 colorspace) and usually 682 limited range for Y'CbCr.</entry> 683 </row> 684 <row> 685 <entry><constant>V4L2_QUANTIZATION_FULL_RANGE</constant></entry> 686 <entry>Use the full range quantization encoding. I.e. the range [0…1] 687 is mapped to [0…255] (with possible clipping to [1…254] to avoid the 688 0x00 and 0xff values). Cb and Cr are mapped from [-0.5…0.5] to [0…255] 689 (with possible clipping to [1…254] to avoid the 0x00 and 0xff values).</entry> 690 </row> 691 <row> 692 <entry><constant>V4L2_QUANTIZATION_LIM_RANGE</constant></entry> 693 <entry>Use the limited range quantization encoding. I.e. the range [0…1] 694 is mapped to [16…235]. Cb and Cr are mapped from [-0.5…0.5] to [16…240]. 695 </entry> 696 </row> 697 </tbody> 698 </tgroup> 699 </table> 700 </section> 701 702 <section> 703 <title>Detailed Colorspace Descriptions</title> 704 <section id="col-smpte-170m"> 705 <title>Colorspace SMPTE 170M (<constant>V4L2_COLORSPACE_SMPTE170M</constant>)</title> 706 <para>The <xref linkend="smpte170m" /> standard defines the colorspace used by NTSC and PAL and by SDTV 707 in general. The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. 708 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. 709 The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and 710 the white reference are:</para> 711 <table frame="none"> 712 <title>SMPTE 170M Chromaticities</title> 713 <tgroup cols="3" align="left"> 714 &cs-str; 715 <thead> 716 <row> 717 <entry>Color</entry> 718 <entry>x</entry> 719 <entry>y</entry> 720 </row> 721 </thead> 722 <tbody valign="top"> 723 <row> 724 <entry>Red</entry> 725 <entry>0.630</entry> 726 <entry>0.340</entry> 727 </row> 728 <row> 729 <entry>Green</entry> 730 <entry>0.310</entry> 731 <entry>0.595</entry> 732 </row> 733 <row> 734 <entry>Blue</entry> 735 <entry>0.155</entry> 736 <entry>0.070</entry> 737 </row> 738 <row> 739 <entry>White Reference (D65)</entry> 740 <entry>0.3127</entry> 741 <entry>0.3290</entry> 742 </row> 743 </tbody> 744 </tgroup> 745 </table> 746 <para>The red, green and blue chromaticities are also often referred to 747 as the SMPTE C set, so this colorspace is sometimes called SMPTE C as well.</para> 748 <variablelist> 749 <varlistentry> 750 <term>The transfer function defined for SMPTE 170M is the same as the 751 one defined in Rec. 709.</term> 752 <listitem> 753 <para>L' = -1.099(-L)<superscript>0.45</superscript> + 0.099 for L ≤ -0.018</para> 754 <para>L' = 4.5L for -0.018 < L < 0.018</para> 755 <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for L ≥ 0.018</para> 756 </listitem> 757 </varlistentry> 758 </variablelist> 759 <variablelist> 760 <varlistentry> 761 <term>Inverse Transfer function:</term> 762 <listitem> 763 <para>L = -((L' - 0.099) / -1.099)<superscript>1/0.45</superscript> for L' ≤ -0.081</para> 764 <para>L = L' / 4.5 for -0.081 < L' < 0.081</para> 765 <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 0.081</para> 766 </listitem> 767 </varlistentry> 768 </variablelist> 769 <variablelist> 770 <varlistentry> 771 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with 772 the following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term> 773 <listitem> 774 <para>Y' = 0.299R' + 0.587G' + 0.114B'</para> 775 <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> 776 <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> 777 </listitem> 778 </varlistentry> 779 </variablelist> 780 <para>Y' is clamped to the range [0…1] and Cb and Cr are 781 clamped to the range [-0.5…0.5]. This conversion to Y'CbCr is identical to the one 782 defined in the <xref linkend="itu601" /> standard and this colorspace is sometimes called BT.601 as well, even 783 though BT.601 does not mention any color primaries.</para> 784 <para>The default quantization is limited range, but full range is possible although 785 rarely seen.</para> 786 </section> 787 788 <section id="col-rec709"> 789 <title>Colorspace Rec. 709 (<constant>V4L2_COLORSPACE_REC709</constant>)</title> 790 <para>The <xref linkend="itu709" /> standard defines the colorspace used by HDTV in general. 791 The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. The default 792 Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_709</constant>. The default Y'CbCr quantization is 793 limited range. The chromaticities of the primary colors and the white reference are:</para> 794 <table frame="none"> 795 <title>Rec. 709 Chromaticities</title> 796 <tgroup cols="3" align="left"> 797 &cs-str; 798 <thead> 799 <row> 800 <entry>Color</entry> 801 <entry>x</entry> 802 <entry>y</entry> 803 </row> 804 </thead> 805 <tbody valign="top"> 806 <row> 807 <entry>Red</entry> 808 <entry>0.640</entry> 809 <entry>0.330</entry> 810 </row> 811 <row> 812 <entry>Green</entry> 813 <entry>0.300</entry> 814 <entry>0.600</entry> 815 </row> 816 <row> 817 <entry>Blue</entry> 818 <entry>0.150</entry> 819 <entry>0.060</entry> 820 </row> 821 <row> 822 <entry>White Reference (D65)</entry> 823 <entry>0.3127</entry> 824 <entry>0.3290</entry> 825 </row> 826 </tbody> 827 </tgroup> 828 </table> 829 <para>The full name of this standard is Rec. ITU-R BT.709-5.</para> 830 <variablelist> 831 <varlistentry> 832 <term>Transfer function. Normally L is in the range [0…1], but for the extended 833 gamut xvYCC encoding values outside that range are allowed.</term> 834 <listitem> 835 <para>L' = -1.099(-L)<superscript>0.45</superscript> + 0.099 for L ≤ -0.018</para> 836 <para>L' = 4.5L for -0.018 < L < 0.018</para> 837 <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for L ≥ 0.018</para> 838 </listitem> 839 </varlistentry> 840 </variablelist> 841 <variablelist> 842 <varlistentry> 843 <term>Inverse Transfer function:</term> 844 <listitem> 845 <para>L = -((L' - 0.099) / -1.099)<superscript>1/0.45</superscript> for L' ≤ -0.081</para> 846 <para>L = L' / 4.5 for -0.081 < L' < 0.081</para> 847 <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 0.081</para> 848 </listitem> 849 </varlistentry> 850 </variablelist> 851 <variablelist> 852 <varlistentry> 853 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following 854 <constant>V4L2_YCBCR_ENC_709</constant> encoding:</term> 855 <listitem> 856 <para>Y' = 0.2126R' + 0.7152G' + 0.0722B'</para> 857 <para>Cb = -0.1146R' - 0.3854G' + 0.5B'</para> 858 <para>Cr = 0.5R' - 0.4542G' - 0.0458B'</para> 859 </listitem> 860 </varlistentry> 861 </variablelist> 862 <para>Y' is clamped to the range [0…1] and Cb and Cr are 863 clamped to the range [-0.5…0.5].</para> 864 <para>The default quantization is limited range, but full range is possible although 865 rarely seen.</para> 866 <para>The <constant>V4L2_YCBCR_ENC_709</constant> encoding described above is the default 867 for this colorspace, but it can be overridden with <constant>V4L2_YCBCR_ENC_601</constant>, in which 868 case the BT.601 Y'CbCr encoding is used.</para> 869 <para>Two additional extended gamut Y'CbCr encodings are also possible with this colorspace:</para> 870 <variablelist> 871 <varlistentry> 872 <term>The xvYCC 709 encoding (<constant>V4L2_YCBCR_ENC_XV709</constant>, <xref linkend="xvycc" />) 873 is similar to the Rec. 709 encoding, but it allows for R', G' and B' values that are outside the range 874 [0…1]. The resulting Y', Cb and Cr values are scaled and offset:</term> 875 <listitem> 876 <para>Y' = (219 / 256) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 256)</para> 877 <para>Cb = (224 / 256) * (-0.1146R' - 0.3854G' + 0.5B')</para> 878 <para>Cr = (224 / 256) * (0.5R' - 0.4542G' - 0.0458B')</para> 879 </listitem> 880 </varlistentry> 881 </variablelist> 882 <variablelist> 883 <varlistentry> 884 <term>The xvYCC 601 encoding (<constant>V4L2_YCBCR_ENC_XV601</constant>, <xref linkend="xvycc" />) is similar 885 to the BT.601 encoding, but it allows for R', G' and B' values that are outside the range 886 [0…1]. The resulting Y', Cb and Cr values are scaled and offset:</term> 887 <listitem> 888 <para>Y' = (219 / 256) * (0.299R' + 0.587G' + 0.114B') + (16 / 256)</para> 889 <para>Cb = (224 / 256) * (-0.169R' - 0.331G' + 0.5B')</para> 890 <para>Cr = (224 / 256) * (0.5R' - 0.419G' - 0.081B')</para> 891 </listitem> 892 </varlistentry> 893 </variablelist> 894 <para>Y' is clamped to the range [0…1] and Cb and Cr are clamped 895 to the range [-0.5…0.5]. The non-standard xvYCC 709 or xvYCC 601 encodings can be used by 896 selecting <constant>V4L2_YCBCR_ENC_XV709</constant> or <constant>V4L2_YCBCR_ENC_XV601</constant>. 897 The xvYCC encodings always use full range quantization.</para> 898 </section> 899 900 <section id="col-srgb"> 901 <title>Colorspace sRGB (<constant>V4L2_COLORSPACE_SRGB</constant>)</title> 902 <para>The <xref linkend="srgb" /> standard defines the colorspace used by most webcams 903 and computer graphics. The default transfer function is <constant>V4L2_XFER_FUNC_SRGB</constant>. 904 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SYCC</constant>. The default Y'CbCr 905 quantization is full range. The chromaticities of the primary colors and the white 906 reference are:</para> 907 <table frame="none"> 908 <title>sRGB Chromaticities</title> 909 <tgroup cols="3" align="left"> 910 &cs-str; 911 <thead> 912 <row> 913 <entry>Color</entry> 914 <entry>x</entry> 915 <entry>y</entry> 916 </row> 917 </thead> 918 <tbody valign="top"> 919 <row> 920 <entry>Red</entry> 921 <entry>0.640</entry> 922 <entry>0.330</entry> 923 </row> 924 <row> 925 <entry>Green</entry> 926 <entry>0.300</entry> 927 <entry>0.600</entry> 928 </row> 929 <row> 930 <entry>Blue</entry> 931 <entry>0.150</entry> 932 <entry>0.060</entry> 933 </row> 934 <row> 935 <entry>White Reference (D65)</entry> 936 <entry>0.3127</entry> 937 <entry>0.3290</entry> 938 </row> 939 </tbody> 940 </tgroup> 941 </table> 942 <para>These chromaticities are identical to the Rec. 709 colorspace.</para> 943 <variablelist> 944 <varlistentry> 945 <term>Transfer function. Note that negative values for L are only used by the Y'CbCr conversion.</term> 946 <listitem> 947 <para>L' = -1.055(-L)<superscript>1/2.4</superscript> + 0.055 for L < -0.0031308</para> 948 <para>L' = 12.92L for -0.0031308 ≤ L ≤ 0.0031308</para> 949 <para>L' = 1.055L<superscript>1/2.4</superscript> - 0.055 for 0.0031308 < L ≤ 1</para> 950 </listitem> 951 </varlistentry> 952 <varlistentry> 953 <term>Inverse Transfer function:</term> 954 <listitem> 955 <para>L = -((-L' + 0.055) / 1.055)<superscript>2.4</superscript> for L' < -0.04045</para> 956 <para>L = L' / 12.92 for -0.04045 ≤ L' ≤ 0.04045</para> 957 <para>L = ((L' + 0.055) / 1.055)<superscript>2.4</superscript> for L' > 0.04045</para> 958 </listitem> 959 </varlistentry> 960 </variablelist> 961 <variablelist> 962 <varlistentry> 963 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following 964 <constant>V4L2_YCBCR_ENC_SYCC</constant> encoding as defined by <xref linkend="sycc" />:</term> 965 <listitem> 966 <para>Y' = 0.2990R' + 0.5870G' + 0.1140B'</para> 967 <para>Cb = -0.1687R' - 0.3313G' + 0.5B'</para> 968 <para>Cr = 0.5R' - 0.4187G' - 0.0813B'</para> 969 </listitem> 970 </varlistentry> 971 </variablelist> 972 <para>Y' is clamped to the range [0…1] and Cb and Cr are clamped 973 to the range [-0.5…0.5]. The <constant>V4L2_YCBCR_ENC_SYCC</constant> quantization is always 974 full range. Although this Y'CbCr encoding looks very similar to the <constant>V4L2_YCBCR_ENC_XV601</constant> 975 encoding, it is not. The <constant>V4L2_YCBCR_ENC_XV601</constant> scales and offsets the Y'CbCr 976 values before quantization, but this encoding does not do that.</para> 977 </section> 978 979 <section id="col-adobergb"> 980 <title>Colorspace Adobe RGB (<constant>V4L2_COLORSPACE_ADOBERGB</constant>)</title> 981 <para>The <xref linkend="adobergb" /> standard defines the colorspace used by computer graphics 982 that use the AdobeRGB colorspace. This is also known as the <xref linkend="oprgb" /> standard. 983 The default transfer function is <constant>V4L2_XFER_FUNC_ADOBERGB</constant>. 984 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. The default Y'CbCr 985 quantization is limited range. The chromaticities of the primary colors and the white reference 986 are:</para> 987 <table frame="none"> 988 <title>Adobe RGB Chromaticities</title> 989 <tgroup cols="3" align="left"> 990 &cs-str; 991 <thead> 992 <row> 993 <entry>Color</entry> 994 <entry>x</entry> 995 <entry>y</entry> 996 </row> 997 </thead> 998 <tbody valign="top"> 999 <row> 1000 <entry>Red</entry> 1001 <entry>0.6400</entry> 1002 <entry>0.3300</entry> 1003 </row> 1004 <row> 1005 <entry>Green</entry> 1006 <entry>0.2100</entry> 1007 <entry>0.7100</entry> 1008 </row> 1009 <row> 1010 <entry>Blue</entry> 1011 <entry>0.1500</entry> 1012 <entry>0.0600</entry> 1013 </row> 1014 <row> 1015 <entry>White Reference (D65)</entry> 1016 <entry>0.3127</entry> 1017 <entry>0.3290</entry> 1018 </row> 1019 </tbody> 1020 </tgroup> 1021 </table> 1022 <variablelist> 1023 <varlistentry> 1024 <term>Transfer function:</term> 1025 <listitem> 1026 <para>L' = L<superscript>1/2.19921875</superscript></para> 1027 </listitem> 1028 </varlistentry> 1029 <varlistentry> 1030 <term>Inverse Transfer function:</term> 1031 <listitem> 1032 <para>L = L'<superscript>2.19921875</superscript></para> 1033 </listitem> 1034 </varlistentry> 1035 </variablelist> 1036 <variablelist> 1037 <varlistentry> 1038 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the 1039 following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term> 1040 <listitem> 1041 <para>Y' = 0.299R' + 0.587G' + 0.114B'</para> 1042 <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> 1043 <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> 1044 </listitem> 1045 </varlistentry> 1046 </variablelist> 1047 <para>Y' is clamped to the range [0…1] and Cb and Cr are 1048 clamped to the range [-0.5…0.5]. This transform is identical to one defined in 1049 SMPTE 170M/BT.601. The Y'CbCr quantization is limited range.</para> 1050 </section> 1051 1052 <section id="col-bt2020"> 1053 <title>Colorspace BT.2020 (<constant>V4L2_COLORSPACE_BT2020</constant>)</title> 1054 <para>The <xref linkend="itu2020" /> standard defines the colorspace used by Ultra-high definition 1055 television (UHDTV). The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. 1056 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_BT2020</constant>. 1057 The default R'G'B' quantization is limited range (!), and so is the default Y'CbCr quantization. 1058 The chromaticities of the primary colors and the white reference are:</para> 1059 <table frame="none"> 1060 <title>BT.2020 Chromaticities</title> 1061 <tgroup cols="3" align="left"> 1062 &cs-str; 1063 <thead> 1064 <row> 1065 <entry>Color</entry> 1066 <entry>x</entry> 1067 <entry>y</entry> 1068 </row> 1069 </thead> 1070 <tbody valign="top"> 1071 <row> 1072 <entry>Red</entry> 1073 <entry>0.708</entry> 1074 <entry>0.292</entry> 1075 </row> 1076 <row> 1077 <entry>Green</entry> 1078 <entry>0.170</entry> 1079 <entry>0.797</entry> 1080 </row> 1081 <row> 1082 <entry>Blue</entry> 1083 <entry>0.131</entry> 1084 <entry>0.046</entry> 1085 </row> 1086 <row> 1087 <entry>White Reference (D65)</entry> 1088 <entry>0.3127</entry> 1089 <entry>0.3290</entry> 1090 </row> 1091 </tbody> 1092 </tgroup> 1093 </table> 1094 <variablelist> 1095 <varlistentry> 1096 <term>Transfer function (same as Rec. 709):</term> 1097 <listitem> 1098 <para>L' = 4.5L for 0 ≤ L < 0.018</para> 1099 <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> 1100 </listitem> 1101 </varlistentry> 1102 <varlistentry> 1103 <term>Inverse Transfer function:</term> 1104 <listitem> 1105 <para>L = L' / 4.5 for L' < 0.081</para> 1106 <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 0.081</para> 1107 </listitem> 1108 </varlistentry> 1109 </variablelist> 1110 <variablelist> 1111 <varlistentry> 1112 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the 1113 following <constant>V4L2_YCBCR_ENC_BT2020</constant> encoding:</term> 1114 <listitem> 1115 <para>Y' = 0.2627R' + 0.6780G' + 0.0593B'</para> 1116 <para>Cb = -0.1396R' - 0.3604G' + 0.5B'</para> 1117 <para>Cr = 0.5R' - 0.4598G' - 0.0402B'</para> 1118 </listitem> 1119 </varlistentry> 1120 </variablelist> 1121 <para>Y' is clamped to the range [0…1] and Cb and Cr are 1122 clamped to the range [-0.5…0.5]. The Y'CbCr quantization is limited range.</para> 1123 <para>There is also an alternate constant luminance R'G'B' to Yc'CbcCrc 1124 (<constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant>) encoding:</para> 1125 <variablelist> 1126 <varlistentry> 1127 <term>Luma:</term> 1128 <listitem> 1129 <para>Yc' = (0.2627R + 0.6780G + 0.0593B)'</para> 1130 </listitem> 1131 </varlistentry> 1132 </variablelist> 1133 <variablelist> 1134 <varlistentry> 1135 <term>B' - Yc' ≤ 0:</term> 1136 <listitem> 1137 <para>Cbc = (B' - Yc') / 1.9404</para> 1138 </listitem> 1139 </varlistentry> 1140 </variablelist> 1141 <variablelist> 1142 <varlistentry> 1143 <term>B' - Yc' > 0:</term> 1144 <listitem> 1145 <para>Cbc = (B' - Yc') / 1.5816</para> 1146 </listitem> 1147 </varlistentry> 1148 </variablelist> 1149 <variablelist> 1150 <varlistentry> 1151 <term>R' - Yc' ≤ 0:</term> 1152 <listitem> 1153 <para>Crc = (R' - Y') / 1.7184</para> 1154 </listitem> 1155 </varlistentry> 1156 </variablelist> 1157 <variablelist> 1158 <varlistentry> 1159 <term>R' - Yc' > 0:</term> 1160 <listitem> 1161 <para>Crc = (R' - Y') / 0.9936</para> 1162 </listitem> 1163 </varlistentry> 1164 </variablelist> 1165 <para>Yc' is clamped to the range [0…1] and Cbc and Crc are 1166 clamped to the range [-0.5…0.5]. The Yc'CbcCrc quantization is limited range.</para> 1167 </section> 1168 1169 <section id="col-dcip3"> 1170 <title>Colorspace DCI-P3 (<constant>V4L2_COLORSPACE_DCI_P3</constant>)</title> 1171 <para>The <xref linkend="smpte431" /> standard defines the colorspace used by cinema 1172 projectors that use the DCI-P3 colorspace. 1173 The default transfer function is <constant>V4L2_XFER_FUNC_DCI_P3</constant>. 1174 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_709</constant>. Note that this 1175 colorspace does not specify a Y'CbCr encoding since it is not meant to be encoded 1176 to Y'CbCr. So this default Y'CbCr encoding was picked because it is the HDTV 1177 encoding. The default Y'CbCr quantization is limited range. The chromaticities of 1178 the primary colors and the white reference are:</para> 1179 <table frame="none"> 1180 <title>DCI-P3 Chromaticities</title> 1181 <tgroup cols="3" align="left"> 1182 &cs-str; 1183 <thead> 1184 <row> 1185 <entry>Color</entry> 1186 <entry>x</entry> 1187 <entry>y</entry> 1188 </row> 1189 </thead> 1190 <tbody valign="top"> 1191 <row> 1192 <entry>Red</entry> 1193 <entry>0.6800</entry> 1194 <entry>0.3200</entry> 1195 </row> 1196 <row> 1197 <entry>Green</entry> 1198 <entry>0.2650</entry> 1199 <entry>0.6900</entry> 1200 </row> 1201 <row> 1202 <entry>Blue</entry> 1203 <entry>0.1500</entry> 1204 <entry>0.0600</entry> 1205 </row> 1206 <row> 1207 <entry>White Reference</entry> 1208 <entry>0.3140</entry> 1209 <entry>0.3510</entry> 1210 </row> 1211 </tbody> 1212 </tgroup> 1213 </table> 1214 <variablelist> 1215 <varlistentry> 1216 <term>Transfer function:</term> 1217 <listitem> 1218 <para>L' = L<superscript>1/2.6</superscript></para> 1219 </listitem> 1220 </varlistentry> 1221 <varlistentry> 1222 <term>Inverse Transfer function:</term> 1223 <listitem> 1224 <para>L = L'<superscript>2.6</superscript></para> 1225 </listitem> 1226 </varlistentry> 1227 </variablelist> 1228 <para>Y'CbCr encoding is not specified. V4L2 defaults to Rec. 709.</para> 1229 </section> 1230 1231 <section id="col-smpte-240m"> 1232 <title>Colorspace SMPTE 240M (<constant>V4L2_COLORSPACE_SMPTE240M</constant>)</title> 1233 <para>The <xref linkend="smpte240m" /> standard was an interim standard used during 1234 the early days of HDTV (1988-1998). It has been superseded by Rec. 709. 1235 The default transfer function is <constant>V4L2_XFER_FUNC_SMPTE240M</constant>. 1236 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SMPTE240M</constant>. 1237 The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and the 1238 white reference are:</para> 1239 <table frame="none"> 1240 <title>SMPTE 240M Chromaticities</title> 1241 <tgroup cols="3" align="left"> 1242 &cs-str; 1243 <thead> 1244 <row> 1245 <entry>Color</entry> 1246 <entry>x</entry> 1247 <entry>y</entry> 1248 </row> 1249 </thead> 1250 <tbody valign="top"> 1251 <row> 1252 <entry>Red</entry> 1253 <entry>0.630</entry> 1254 <entry>0.340</entry> 1255 </row> 1256 <row> 1257 <entry>Green</entry> 1258 <entry>0.310</entry> 1259 <entry>0.595</entry> 1260 </row> 1261 <row> 1262 <entry>Blue</entry> 1263 <entry>0.155</entry> 1264 <entry>0.070</entry> 1265 </row> 1266 <row> 1267 <entry>White Reference (D65)</entry> 1268 <entry>0.3127</entry> 1269 <entry>0.3290</entry> 1270 </row> 1271 </tbody> 1272 </tgroup> 1273 </table> 1274 <para>These chromaticities are identical to the SMPTE 170M colorspace.</para> 1275 <variablelist> 1276 <varlistentry> 1277 <term>Transfer function:</term> 1278 <listitem> 1279 <para>L' = 4L for 0 ≤ L < 0.0228</para> 1280 <para>L' = 1.1115L<superscript>0.45</superscript> - 0.1115 for 0.0228 ≤ L ≤ 1</para> 1281 </listitem> 1282 </varlistentry> 1283 <varlistentry> 1284 <term>Inverse Transfer function:</term> 1285 <listitem> 1286 <para>L = L' / 4 for 0 ≤ L' < 0.0913</para> 1287 <para>L = ((L' + 0.1115) / 1.1115)<superscript>1/0.45</superscript> for L' ≥ 0.0913</para> 1288 </listitem> 1289 </varlistentry> 1290 </variablelist> 1291 <variablelist> 1292 <varlistentry> 1293 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the 1294 following <constant>V4L2_YCBCR_ENC_SMPTE240M</constant> encoding:</term> 1295 <listitem> 1296 <para>Y' = 0.2122R' + 0.7013G' + 0.0865B'</para> 1297 <para>Cb = -0.1161R' - 0.3839G' + 0.5B'</para> 1298 <para>Cr = 0.5R' - 0.4451G' - 0.0549B'</para> 1299 </listitem> 1300 </varlistentry> 1301 </variablelist> 1302 <para>Yc' is clamped to the range [0…1] and Cbc and Crc are 1303 clamped to the range [-0.5…0.5]. The Y'CbCr quantization is limited range.</para> 1304 </section> 1305 1306 <section id="col-sysm"> 1307 <title>Colorspace NTSC 1953 (<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant>)</title> 1308 <para>This standard defines the colorspace used by NTSC in 1953. In practice this 1309 colorspace is obsolete and SMPTE 170M should be used instead. 1310 The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. 1311 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. 1312 The default Y'CbCr quantization is limited range. 1313 The chromaticities of the primary colors and the white reference are:</para> 1314 <table frame="none"> 1315 <title>NTSC 1953 Chromaticities</title> 1316 <tgroup cols="3" align="left"> 1317 &cs-str; 1318 <thead> 1319 <row> 1320 <entry>Color</entry> 1321 <entry>x</entry> 1322 <entry>y</entry> 1323 </row> 1324 </thead> 1325 <tbody valign="top"> 1326 <row> 1327 <entry>Red</entry> 1328 <entry>0.67</entry> 1329 <entry>0.33</entry> 1330 </row> 1331 <row> 1332 <entry>Green</entry> 1333 <entry>0.21</entry> 1334 <entry>0.71</entry> 1335 </row> 1336 <row> 1337 <entry>Blue</entry> 1338 <entry>0.14</entry> 1339 <entry>0.08</entry> 1340 </row> 1341 <row> 1342 <entry>White Reference (C)</entry> 1343 <entry>0.310</entry> 1344 <entry>0.316</entry> 1345 </row> 1346 </tbody> 1347 </tgroup> 1348 </table> 1349 <para>Note that this colorspace uses Illuminant C instead of D65 as the 1350 white reference. To correctly convert an image in this colorspace to another 1351 that uses D65 you need to apply a chromatic adaptation algorithm such as the 1352 Bradford method.</para> 1353 <variablelist> 1354 <varlistentry> 1355 <term>The transfer function was never properly defined for NTSC 1953. The 1356 Rec. 709 transfer function is recommended in the literature:</term> 1357 <listitem> 1358 <para>L' = 4.5L for 0 ≤ L < 0.018</para> 1359 <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> 1360 </listitem> 1361 </varlistentry> 1362 <varlistentry> 1363 <term>Inverse Transfer function:</term> 1364 <listitem> 1365 <para>L = L' / 4.5 for L' < 0.081</para> 1366 <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 0.081</para> 1367 </listitem> 1368 </varlistentry> 1369 </variablelist> 1370 <variablelist> 1371 <varlistentry> 1372 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the 1373 following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term> 1374 <listitem> 1375 <para>Y' = 0.299R' + 0.587G' + 0.114B'</para> 1376 <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> 1377 <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> 1378 </listitem> 1379 </varlistentry> 1380 </variablelist> 1381 <para>Y' is clamped to the range [0…1] and Cb and Cr are 1382 clamped to the range [-0.5…0.5]. The Y'CbCr quantization is limited range. 1383 This transform is identical to one defined in SMPTE 170M/BT.601.</para> 1384 </section> 1385 1386 <section id="col-sysbg"> 1387 <title>Colorspace EBU Tech. 3213 (<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant>)</title> 1388 <para>The <xref linkend="tech3213" /> standard defines the colorspace used by PAL/SECAM in 1975. In practice this 1389 colorspace is obsolete and SMPTE 170M should be used instead. 1390 The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. 1391 The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. 1392 The default Y'CbCr quantization is limited range. 1393 The chromaticities of the primary colors and the white reference are:</para> 1394 <table frame="none"> 1395 <title>EBU Tech. 3213 Chromaticities</title> 1396 <tgroup cols="3" align="left"> 1397 &cs-str; 1398 <thead> 1399 <row> 1400 <entry>Color</entry> 1401 <entry>x</entry> 1402 <entry>y</entry> 1403 </row> 1404 </thead> 1405 <tbody valign="top"> 1406 <row> 1407 <entry>Red</entry> 1408 <entry>0.64</entry> 1409 <entry>0.33</entry> 1410 </row> 1411 <row> 1412 <entry>Green</entry> 1413 <entry>0.29</entry> 1414 <entry>0.60</entry> 1415 </row> 1416 <row> 1417 <entry>Blue</entry> 1418 <entry>0.15</entry> 1419 <entry>0.06</entry> 1420 </row> 1421 <row> 1422 <entry>White Reference (D65)</entry> 1423 <entry>0.3127</entry> 1424 <entry>0.3290</entry> 1425 </row> 1426 </tbody> 1427 </tgroup> 1428 </table> 1429 <variablelist> 1430 <varlistentry> 1431 <term>The transfer function was never properly defined for this colorspace. 1432 The Rec. 709 transfer function is recommended in the literature:</term> 1433 <listitem> 1434 <para>L' = 4.5L for 0 ≤ L < 0.018</para> 1435 <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> 1436 </listitem> 1437 </varlistentry> 1438 <varlistentry> 1439 <term>Inverse Transfer function:</term> 1440 <listitem> 1441 <para>L = L' / 4.5 for L' < 0.081</para> 1442 <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 0.081</para> 1443 </listitem> 1444 </varlistentry> 1445 </variablelist> 1446 <variablelist> 1447 <varlistentry> 1448 <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the 1449 following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term> 1450 <listitem> 1451 <para>Y' = 0.299R' + 0.587G' + 0.114B'</para> 1452 <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> 1453 <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> 1454 </listitem> 1455 </varlistentry> 1456 </variablelist> 1457 <para>Y' is clamped to the range [0…1] and Cb and Cr are 1458 clamped to the range [-0.5…0.5]. The Y'CbCr quantization is limited range. 1459 This transform is identical to one defined in SMPTE 170M/BT.601.</para> 1460 </section> 1461 1462 <section id="col-jpeg"> 1463 <title>Colorspace JPEG (<constant>V4L2_COLORSPACE_JPEG</constant>)</title> 1464 <para>This colorspace defines the colorspace used by most (Motion-)JPEG formats. The chromaticities 1465 of the primary colors and the white reference are identical to sRGB. The transfer 1466 function use is <constant>V4L2_XFER_FUNC_SRGB</constant>. The Y'CbCr encoding is 1467 <constant>V4L2_YCBCR_ENC_601</constant> with full range quantization where 1468 Y' is scaled to [0…255] and Cb/Cr are scaled to [-128…128] and 1469 then clipped to [-128…127].</para> 1470 <para>Note that the JPEG standard does not actually store colorspace information. 1471 So if something other than sRGB is used, then the driver will have to set that information 1472 explicitly. Effectively <constant>V4L2_COLORSPACE_JPEG</constant> can be considered to be 1473 an abbreviation for <constant>V4L2_COLORSPACE_SRGB</constant>, <constant>V4L2_YCBCR_ENC_601</constant> 1474 and <constant>V4L2_QUANTIZATION_FULL_RANGE</constant>.</para> 1475 </section> 1476 1477 </section> 1478 1479 <section> 1480 <title>Detailed Transfer Function Descriptions</title> 1481 <section id="xf-smpte-2084"> 1482 <title>Transfer Function SMPTE 2084 (<constant>V4L2_XFER_FUNC_SMPTE2084</constant>)</title> 1483 <para>The <xref linkend="smpte2084" /> standard defines the transfer function used by 1484 High Dynamic Range content.</para> 1485 <variablelist> 1486 <varlistentry> 1487 <term>Constants:</term> 1488 <listitem> 1489 <para>m1 = (2610 / 4096) / 4</para> 1490 <para>m2 = (2523 / 4096) * 128</para> 1491 <para>c1 = 3424 / 4096</para> 1492 <para>c2 = (2413 / 4096) * 32</para> 1493 <para>c3 = (2392 / 4096) * 32</para> 1494 </listitem> 1495 </varlistentry> 1496 <varlistentry> 1497 <term>Transfer function:</term> 1498 <listitem> 1499 <para>L' = ((c1 + c2 * L<superscript>m1</superscript>) / (1 + c3 * L<superscript>m1</superscript>))<superscript>m2</superscript></para> 1500 </listitem> 1501 </varlistentry> 1502 </variablelist> 1503 <variablelist> 1504 <varlistentry> 1505 <term>Inverse Transfer function:</term> 1506 <listitem> 1507 <para>L = (max(L'<superscript>1/m2</superscript> - c1, 0) / (c2 - c3 * L'<superscript>1/m2</superscript>))<superscript>1/m1</superscript></para> 1508 </listitem> 1509 </varlistentry> 1510 </variablelist> 1511 </section> 1512 </section> 1513 1514 <section id="pixfmt-indexed"> 1515 <title>Indexed Format</title> 1516 1517 <para>In this format each pixel is represented by an 8 bit index 1518 into a 256 entry ARGB palette. It is intended for <link 1519 linkend="osd">Video Output Overlays</link> only. There are no ioctls to 1520 access the palette, this must be done with ioctls of the Linux framebuffer API.</para> 1521 1522 <table pgwide="0" frame="none"> 1523 <title>Indexed Image Format</title> 1524 <tgroup cols="37" align="center"> 1525 <colspec colname="id" align="left" /> 1526 <colspec colname="fourcc" /> 1527 <colspec colname="bit" /> 1528 1529 <colspec colnum="4" colname="b07" align="center" /> 1530 <colspec colnum="5" colname="b06" align="center" /> 1531 <colspec colnum="6" colname="b05" align="center" /> 1532 <colspec colnum="7" colname="b04" align="center" /> 1533 <colspec colnum="8" colname="b03" align="center" /> 1534 <colspec colnum="9" colname="b02" align="center" /> 1535 <colspec colnum="10" colname="b01" align="center" /> 1536 <colspec colnum="11" colname="b00" align="center" /> 1537 1538 <spanspec namest="b07" nameend="b00" spanname="b0" /> 1539 <spanspec namest="b17" nameend="b10" spanname="b1" /> 1540 <spanspec namest="b27" nameend="b20" spanname="b2" /> 1541 <spanspec namest="b37" nameend="b30" spanname="b3" /> 1542 <thead> 1543 <row> 1544 <entry>Identifier</entry> 1545 <entry>Code</entry> 1546 <entry> </entry> 1547 <entry spanname="b0">Byte 0</entry> 1548 </row> 1549 <row> 1550 <entry> </entry> 1551 <entry> </entry> 1552 <entry>Bit</entry> 1553 <entry>7</entry> 1554 <entry>6</entry> 1555 <entry>5</entry> 1556 <entry>4</entry> 1557 <entry>3</entry> 1558 <entry>2</entry> 1559 <entry>1</entry> 1560 <entry>0</entry> 1561 </row> 1562 </thead> 1563 <tbody valign="top"> 1564 <row id="V4L2-PIX-FMT-PAL8"> 1565 <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry> 1566 <entry>'PAL8'</entry> 1567 <entry></entry> 1568 <entry>i<subscript>7</subscript></entry> 1569 <entry>i<subscript>6</subscript></entry> 1570 <entry>i<subscript>5</subscript></entry> 1571 <entry>i<subscript>4</subscript></entry> 1572 <entry>i<subscript>3</subscript></entry> 1573 <entry>i<subscript>2</subscript></entry> 1574 <entry>i<subscript>1</subscript></entry> 1575 <entry>i<subscript>0</subscript></entry> 1576 </row> 1577 </tbody> 1578 </tgroup> 1579 </table> 1580 </section> 1581 1582 <section id="pixfmt-rgb"> 1583 <title>RGB Formats</title> 1584 1585 &sub-packed-rgb; 1586 &sub-sbggr8; 1587 &sub-sgbrg8; 1588 &sub-sgrbg8; 1589 &sub-srggb8; 1590 &sub-sbggr16; 1591 &sub-srggb10; 1592 &sub-srggb10p; 1593 &sub-srggb10alaw8; 1594 &sub-srggb10dpcm8; 1595 &sub-srggb12; 1596 </section> 1597 1598 <section id="yuv-formats"> 1599 <title>YUV Formats</title> 1600 1601 <para>YUV is the format native to TV broadcast and composite video 1602 signals. It separates the brightness information (Y) from the color 1603 information (U and V or Cb and Cr). The color information consists of 1604 red and blue <emphasis>color difference</emphasis> signals, this way 1605 the green component can be reconstructed by subtracting from the 1606 brightness component. See <xref linkend="colorspaces" /> for conversion 1607 examples. YUV was chosen because early television would only transmit 1608 brightness information. To add color in a way compatible with existing 1609 receivers a new signal carrier was added to transmit the color 1610 difference signals. Secondary in the YUV format the U and V components 1611 usually have lower resolution than the Y component. This is an analog 1612 video compression technique taking advantage of a property of the 1613 human visual system, being more sensitive to brightness 1614 information.</para> 1615 1616 &sub-packed-yuv; 1617 &sub-grey; 1618 &sub-y10; 1619 &sub-y12; 1620 &sub-y10b; 1621 &sub-y16; 1622 &sub-y16-be; 1623 &sub-y8i; 1624 &sub-y12i; 1625 &sub-uv8; 1626 &sub-yuyv; 1627 &sub-uyvy; 1628 &sub-yvyu; 1629 &sub-vyuy; 1630 &sub-y41p; 1631 &sub-yuv420; 1632 &sub-yuv420m; 1633 &sub-yuv422m; 1634 &sub-yuv444m; 1635 &sub-yuv410; 1636 &sub-yuv422p; 1637 &sub-yuv411p; 1638 &sub-nv12; 1639 &sub-nv12m; 1640 &sub-nv12mt; 1641 &sub-nv16; 1642 &sub-nv16m; 1643 &sub-nv24; 1644 &sub-m420; 1645 </section> 1646 1647 <section id="depth-formats"> 1648 <title>Depth Formats</title> 1649 <para>Depth data provides distance to points, mapped onto the image plane 1650 </para> 1651 1652 &sub-z16; 1653 </section> 1654 1655 <section> 1656 <title>Compressed Formats</title> 1657 1658 <table pgwide="1" frame="none" id="compressed-formats"> 1659 <title>Compressed Image Formats</title> 1660 <tgroup cols="3" align="left"> 1661 &cs-def; 1662 <thead> 1663 <row> 1664 <entry>Identifier</entry> 1665 <entry>Code</entry> 1666 <entry>Details</entry> 1667 </row> 1668 </thead> 1669 <tbody valign="top"> 1670 <row id="V4L2-PIX-FMT-JPEG"> 1671 <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry> 1672 <entry>'JPEG'</entry> 1673 <entry>TBD. See also &VIDIOC-G-JPEGCOMP;, 1674 &VIDIOC-S-JPEGCOMP;.</entry> 1675 </row> 1676 <row id="V4L2-PIX-FMT-MPEG"> 1677 <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry> 1678 <entry>'MPEG'</entry> 1679 <entry>MPEG multiplexed stream. The actual format is determined by 1680 extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see 1681 <xref linkend="mpeg-control-id" />.</entry> 1682 </row> 1683 <row id="V4L2-PIX-FMT-H264"> 1684 <entry><constant>V4L2_PIX_FMT_H264</constant></entry> 1685 <entry>'H264'</entry> 1686 <entry>H264 video elementary stream with start codes.</entry> 1687 </row> 1688 <row id="V4L2-PIX-FMT-H264-NO-SC"> 1689 <entry><constant>V4L2_PIX_FMT_H264_NO_SC</constant></entry> 1690 <entry>'AVC1'</entry> 1691 <entry>H264 video elementary stream without start codes.</entry> 1692 </row> 1693 <row id="V4L2-PIX-FMT-H264-MVC"> 1694 <entry><constant>V4L2_PIX_FMT_H264_MVC</constant></entry> 1695 <entry>'M264'</entry> 1696 <entry>H264 MVC video elementary stream.</entry> 1697 </row> 1698 <row id="V4L2-PIX-FMT-H263"> 1699 <entry><constant>V4L2_PIX_FMT_H263</constant></entry> 1700 <entry>'H263'</entry> 1701 <entry>H263 video elementary stream.</entry> 1702 </row> 1703 <row id="V4L2-PIX-FMT-MPEG1"> 1704 <entry><constant>V4L2_PIX_FMT_MPEG1</constant></entry> 1705 <entry>'MPG1'</entry> 1706 <entry>MPEG1 video elementary stream.</entry> 1707 </row> 1708 <row id="V4L2-PIX-FMT-MPEG2"> 1709 <entry><constant>V4L2_PIX_FMT_MPEG2</constant></entry> 1710 <entry>'MPG2'</entry> 1711 <entry>MPEG2 video elementary stream.</entry> 1712 </row> 1713 <row id="V4L2-PIX-FMT-MPEG4"> 1714 <entry><constant>V4L2_PIX_FMT_MPEG4</constant></entry> 1715 <entry>'MPG4'</entry> 1716 <entry>MPEG4 video elementary stream.</entry> 1717 </row> 1718 <row id="V4L2-PIX-FMT-XVID"> 1719 <entry><constant>V4L2_PIX_FMT_XVID</constant></entry> 1720 <entry>'XVID'</entry> 1721 <entry>Xvid video elementary stream.</entry> 1722 </row> 1723 <row id="V4L2-PIX-FMT-VC1-ANNEX-G"> 1724 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_G</constant></entry> 1725 <entry>'VC1G'</entry> 1726 <entry>VC1, SMPTE 421M Annex G compliant stream.</entry> 1727 </row> 1728 <row id="V4L2-PIX-FMT-VC1-ANNEX-L"> 1729 <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_L</constant></entry> 1730 <entry>'VC1L'</entry> 1731 <entry>VC1, SMPTE 421M Annex L compliant stream.</entry> 1732 </row> 1733 <row id="V4L2-PIX-FMT-VP8"> 1734 <entry><constant>V4L2_PIX_FMT_VP8</constant></entry> 1735 <entry>'VP80'</entry> 1736 <entry>VP8 video elementary stream.</entry> 1737 </row> 1738 </tbody> 1739 </tgroup> 1740 </table> 1741 </section> 1742 1743 <section id="sdr-formats"> 1744 <title>SDR Formats</title> 1745 1746 <para>These formats are used for <link linkend="sdr">SDR</link> 1747 interface only.</para> 1748 1749 &sub-sdr-cu08; 1750 &sub-sdr-cu16le; 1751 &sub-sdr-cs08; 1752 &sub-sdr-cs14le; 1753 &sub-sdr-ru12le; 1754 1755 </section> 1756 1757 <section id="pixfmt-reserved"> 1758 <title>Reserved Format Identifiers</title> 1759 1760 <para>These formats are not defined by this specification, they 1761 are just listed for reference and to avoid naming conflicts. If you 1762 want to register your own format, send an e-mail to the linux-media mailing 1763 list &v4l-ml; for inclusion in the <filename>videodev2.h</filename> 1764 file. If you want to share your format with other developers add a 1765 link to your documentation and send a copy to the linux-media mailing list 1766 for inclusion in this section. If you think your format should be listed 1767 in a standard format section please make a proposal on the linux-media mailing 1768 list.</para> 1769 1770 <table pgwide="1" frame="none" id="reserved-formats"> 1771 <title>Reserved Image Formats</title> 1772 <tgroup cols="3" align="left"> 1773 &cs-def; 1774 <thead> 1775 <row> 1776 <entry>Identifier</entry> 1777 <entry>Code</entry> 1778 <entry>Details</entry> 1779 </row> 1780 </thead> 1781 <tbody valign="top"> 1782 <row id="V4L2-PIX-FMT-DV"> 1783 <entry><constant>V4L2_PIX_FMT_DV</constant></entry> 1784 <entry>'dvsd'</entry> 1785 <entry>unknown</entry> 1786 </row> 1787 <row id="V4L2-PIX-FMT-ET61X251"> 1788 <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry> 1789 <entry>'E625'</entry> 1790 <entry>Compressed format of the ET61X251 driver.</entry> 1791 </row> 1792 <row id="V4L2-PIX-FMT-HI240"> 1793 <entry><constant>V4L2_PIX_FMT_HI240</constant></entry> 1794 <entry>'HI24'</entry> 1795 <entry><para>8 bit RGB format used by the BTTV driver.</para></entry> 1796 </row> 1797 <row id="V4L2-PIX-FMT-HM12"> 1798 <entry><constant>V4L2_PIX_FMT_HM12</constant></entry> 1799 <entry>'HM12'</entry> 1800 <entry><para>YUV 4:2:0 format used by the 1801 IVTV driver, <ulink url="http://www.ivtvdriver.org/"> 1802 http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the 1803 kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename> 1804 </para></entry> 1805 </row> 1806 <row id="V4L2-PIX-FMT-CPIA1"> 1807 <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry> 1808 <entry>'CPIA'</entry> 1809 <entry>YUV format used by the gspca cpia1 driver.</entry> 1810 </row> 1811 <row id="V4L2-PIX-FMT-JPGL"> 1812 <entry><constant>V4L2_PIX_FMT_JPGL</constant></entry> 1813 <entry>'JPGL'</entry> 1814 <entry>JPEG-Light format (Pegasus Lossless JPEG) 1815 used in Divio webcams NW 80x.</entry> 1816 </row> 1817 <row id="V4L2-PIX-FMT-SPCA501"> 1818 <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry> 1819 <entry>'S501'</entry> 1820 <entry>YUYV per line used by the gspca driver.</entry> 1821 </row> 1822 <row id="V4L2-PIX-FMT-SPCA505"> 1823 <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry> 1824 <entry>'S505'</entry> 1825 <entry>YYUV per line used by the gspca driver.</entry> 1826 </row> 1827 <row id="V4L2-PIX-FMT-SPCA508"> 1828 <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry> 1829 <entry>'S508'</entry> 1830 <entry>YUVY per line used by the gspca driver.</entry> 1831 </row> 1832 <row id="V4L2-PIX-FMT-SPCA561"> 1833 <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry> 1834 <entry>'S561'</entry> 1835 <entry>Compressed GBRG Bayer format used by the gspca driver.</entry> 1836 </row> 1837 <row id="V4L2-PIX-FMT-PAC207"> 1838 <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry> 1839 <entry>'P207'</entry> 1840 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 1841 </row> 1842 <row id="V4L2-PIX-FMT-MR97310A"> 1843 <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry> 1844 <entry>'M310'</entry> 1845 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 1846 </row> 1847 <row id="V4L2-PIX-FMT-JL2005BCD"> 1848 <entry><constant>V4L2_PIX_FMT_JL2005BCD</constant></entry> 1849 <entry>'JL20'</entry> 1850 <entry>JPEG compressed RGGB Bayer format used by the gspca driver.</entry> 1851 </row> 1852 <row id="V4L2-PIX-FMT-OV511"> 1853 <entry><constant>V4L2_PIX_FMT_OV511</constant></entry> 1854 <entry>'O511'</entry> 1855 <entry>OV511 JPEG format used by the gspca driver.</entry> 1856 </row> 1857 <row id="V4L2-PIX-FMT-OV518"> 1858 <entry><constant>V4L2_PIX_FMT_OV518</constant></entry> 1859 <entry>'O518'</entry> 1860 <entry>OV518 JPEG format used by the gspca driver.</entry> 1861 </row> 1862 <row id="V4L2-PIX-FMT-PJPG"> 1863 <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry> 1864 <entry>'PJPG'</entry> 1865 <entry>Pixart 73xx JPEG format used by the gspca driver.</entry> 1866 </row> 1867 <row id="V4L2-PIX-FMT-SE401"> 1868 <entry><constant>V4L2_PIX_FMT_SE401</constant></entry> 1869 <entry>'S401'</entry> 1870 <entry>Compressed RGB format used by the gspca se401 driver</entry> 1871 </row> 1872 <row id="V4L2-PIX-FMT-SQ905C"> 1873 <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry> 1874 <entry>'905C'</entry> 1875 <entry>Compressed RGGB bayer format used by the gspca driver.</entry> 1876 </row> 1877 <row id="V4L2-PIX-FMT-MJPEG"> 1878 <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry> 1879 <entry>'MJPG'</entry> 1880 <entry>Compressed format used by the Zoran driver</entry> 1881 </row> 1882 <row id="V4L2-PIX-FMT-PWC1"> 1883 <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry> 1884 <entry>'PWC1'</entry> 1885 <entry>Compressed format of the PWC driver.</entry> 1886 </row> 1887 <row id="V4L2-PIX-FMT-PWC2"> 1888 <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry> 1889 <entry>'PWC2'</entry> 1890 <entry>Compressed format of the PWC driver.</entry> 1891 </row> 1892 <row id="V4L2-PIX-FMT-SN9C10X"> 1893 <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry> 1894 <entry>'S910'</entry> 1895 <entry>Compressed format of the SN9C102 driver.</entry> 1896 </row> 1897 <row id="V4L2-PIX-FMT-SN9C20X-I420"> 1898 <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry> 1899 <entry>'S920'</entry> 1900 <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry> 1901 </row> 1902 <row id="V4L2-PIX-FMT-SN9C2028"> 1903 <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry> 1904 <entry>'SONX'</entry> 1905 <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry> 1906 </row> 1907 <row id="V4L2-PIX-FMT-STV0680"> 1908 <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry> 1909 <entry>'S680'</entry> 1910 <entry>Bayer format of the gspca stv0680 driver.</entry> 1911 </row> 1912 <row id="V4L2-PIX-FMT-WNVA"> 1913 <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry> 1914 <entry>'WNVA'</entry> 1915 <entry><para>Used by the Winnov Videum driver, <ulink 1916 url="http://www.thedirks.org/winnov/"> 1917 http://www.thedirks.org/winnov/</ulink></para></entry> 1918 </row> 1919 <row id="V4L2-PIX-FMT-TM6000"> 1920 <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry> 1921 <entry>'TM60'</entry> 1922 <entry><para>Used by Trident tm6000</para></entry> 1923 </row> 1924 <row id="V4L2-PIX-FMT-CIT-YYVYUY"> 1925 <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry> 1926 <entry>'CITV'</entry> 1927 <entry><para>Used by xirlink CIT, found at IBM webcams.</para> 1928 <para>Uses one line of Y then 1 line of VYUY</para> 1929 </entry> 1930 </row> 1931 <row id="V4L2-PIX-FMT-KONICA420"> 1932 <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry> 1933 <entry>'KONI'</entry> 1934 <entry><para>Used by Konica webcams.</para> 1935 <para>YUV420 planar in blocks of 256 pixels.</para> 1936 </entry> 1937 </row> 1938 <row id="V4L2-PIX-FMT-YYUV"> 1939 <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry> 1940 <entry>'YYUV'</entry> 1941 <entry>unknown</entry> 1942 </row> 1943 <row id="V4L2-PIX-FMT-Y4"> 1944 <entry><constant>V4L2_PIX_FMT_Y4</constant></entry> 1945 <entry>'Y04 '</entry> 1946 <entry>Old 4-bit greyscale format. Only the most significant 4 bits of each byte are used, 1947 the other bits are set to 0.</entry> 1948 </row> 1949 <row id="V4L2-PIX-FMT-Y6"> 1950 <entry><constant>V4L2_PIX_FMT_Y6</constant></entry> 1951 <entry>'Y06 '</entry> 1952 <entry>Old 6-bit greyscale format. Only the most significant 6 bits of each byte are used, 1953 the other bits are set to 0.</entry> 1954 </row> 1955 <row id="V4L2-PIX-FMT-S5C-UYVY-JPG"> 1956 <entry><constant>V4L2_PIX_FMT_S5C_UYVY_JPG</constant></entry> 1957 <entry>'S5CI'</entry> 1958 <entry>Two-planar format used by Samsung S5C73MX cameras. The 1959 first plane contains interleaved JPEG and UYVY image data, followed by meta data 1960 in form of an array of offsets to the UYVY data blocks. The actual pointer array 1961 follows immediately the interleaved JPEG/UYVY data, the number of entries in 1962 this array equals the height of the UYVY image. Each entry is a 4-byte unsigned 1963 integer in big endian order and it's an offset to a single pixel line of the 1964 UYVY image. The first plane can start either with JPEG or UYVY data chunk. The 1965 size of a single UYVY block equals the UYVY image's width multiplied by 2. The 1966 size of a JPEG chunk depends on the image and can vary with each line. 1967 <para>The second plane, at an offset of 4084 bytes, contains a 4-byte offset to 1968 the pointer array in the first plane. This offset is followed by a 4-byte value 1969 indicating size of the pointer array. All numbers in the second plane are also 1970 in big endian order. Remaining data in the second plane is undefined. The 1971 information in the second plane allows to easily find location of the pointer 1972 array, which can be different for each frame. The size of the pointer array is 1973 constant for given UYVY image height.</para> 1974 <para>In order to extract UYVY and JPEG frames an application can initially set 1975 a data pointer to the start of first plane and then add an offset from the first 1976 entry of the pointers table. Such a pointer indicates start of an UYVY image 1977 pixel line. Whole UYVY line can be copied to a separate buffer. These steps 1978 should be repeated for each line, i.e. the number of entries in the pointer 1979 array. Anything what's in between the UYVY lines is JPEG data and should be 1980 concatenated to form the JPEG stream. </para> 1981 </entry> 1982 </row> 1983 </tbody> 1984 </tgroup> 1985 </table> 1986 1987 <table frame="none" pgwide="1" id="format-flags"> 1988 <title>Format Flags</title> 1989 <tgroup cols="3"> 1990 &cs-def; 1991 <tbody valign="top"> 1992 <row> 1993 <entry><constant>V4L2_PIX_FMT_FLAG_PREMUL_ALPHA</constant></entry> 1994 <entry>0x00000001</entry> 1995 <entry>The color values are premultiplied by the alpha channel 1996 value. For example, if a light blue pixel with 50% transparency was described by 1997 RGBA values (128, 192, 255, 128), the same pixel described with premultiplied 1998 colors would be described by RGBA values (64, 96, 128, 128) </entry> 1999 </row> 2000 </tbody> 2001 </tgroup> 2002 </table> 2003 </section>
