Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 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.</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> 114 115 <section> 116 <title>Multi-planar format structures</title> 117 <para>The <structname>v4l2_plane_pix_format</structname> structures define 118 size and layout for each of the planes in a multi-planar format. 119 The <structname>v4l2_pix_format_mplane</structname> structure contains 120 information common to all planes (such as image width and height) and 121 an array of <structname>v4l2_plane_pix_format</structname> structures, 122 describing all planes of that format.</para> 123 <table pgwide="1" frame="none" id="v4l2-plane-pix-format"> 124 <title>struct <structname>vl42_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> 205 206 <section> 207 <title>Standard Image Formats</title> 208 209 <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> 214 215 <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> 224 225 <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> 228 229 <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> 239 240 <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> 246 247 <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> 255 256 <section id="colorspaces"> 257 <title>Colorspaces</title> 258 259 <para>[intro]</para> 260 261 <!-- See proposal by Billy Biggs, video4linux-list@redhat.com 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 --> 265 266 <para> 267 <variablelist> 268 <varlistentry> 269 <term>Gamma Correction</term> 270 <listitem> 271 <para>[to do]</para> 272 <para>E'<subscript>R</subscript> = f(R)</para> 273 <para>E'<subscript>G</subscript> = f(G)</para> 274 <para>E'<subscript>B</subscript> = f(B)</para> 275 </listitem> 276 </varlistentry> 277 <varlistentry> 278 <term>Construction of luminance and color-difference 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> 331 332 <example> 333 <title>ITU-R Rec. BT.601 color conversion</title> 334 335 <para>Forward Transformation</para> 336 337 <programlisting> 338 int ER, EG, EB; /* gamma corrected RGB input [0;255] */ 339 int Y1, Cb, Cr; /* output [0;255] */ 340 341 double r, g, b; /* temporaries */ 342 double y1, pb, pr; 343 344 int 345 clamp (double x) 346 { 347 int r = x; /* round to nearest */ 348 349 if (r < 0) return 0; 350 else if (r > 255) return 255; 351 else return r; 352 } 353 354 r = ER / 255.0; 355 g = EG / 255.0; 356 b = EB / 255.0; 357 358 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; 361 362 Y1 = clamp (219 * y1 + 16); 363 Cb = clamp (224 * pb + 128); 364 Cr = clamp (224 * pr + 128); 365 366 /* or shorter */ 367 368 y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB; 369 370 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> 374 375 <para>Inverse Transformation</para> 376 377 <programlisting> 378 int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */ 379 int ER, EG, EB; /* output [0;255] */ 380 381 double r, g, b; /* temporaries */ 382 double y1, pb, pr; 383 384 int 385 clamp (double x) 386 { 387 int r = x; /* round to nearest */ 388 389 if (r < 0) return 0; 390 else if (r > 255) return 255; 391 else return r; 392 } 393 394 y1 = (255 / 219.0) * (Y1 - 16); 395 pb = (255 / 224.0) * (Cb - 128); 396 pr = (255 / 224.0) * (Cr - 128); 397 398 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; 401 402 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> 407 408 <table pgwide="1" id="v4l2-colorspace" orient="land"> 409 <title>enum v4l2_colorspace</title> 410 <tgroup cols="11" align="center"> 411 <colspec align="left" /> 412 <colspec align="center" /> 413 <colspec align="left" /> 414 <colspec colname="cr" /> 415 <colspec colname="cg" /> 416 <colspec colname="cb" /> 417 <colspec colname="wp" /> 418 <colspec colname="gc" /> 419 <colspec colname="lum" /> 420 <colspec colname="qy" /> 421 <colspec colname="qc" /> 422 <spanspec namest="cr" nameend="cb" spanname="chrom" /> 423 <spanspec namest="qy" nameend="qc" spanname="quant" /> 424 <spanspec namest="lum" nameend="qc" spanname="spam" /> 425 <thead> 426 <row> 427 <entry morerows="1">Identifier</entry> 428 <entry morerows="1">Value</entry> 429 <entry morerows="1">Description</entry> 430 <entry spanname="chrom">Chromaticities<footnote> 431 <para>The coordinates of the color primaries are 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> 597 598 <section id="pixfmt-indexed"> 599 <title>Indexed Format</title> 600 601 <para>In this format each pixel is represented by an 8 bit index 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> 605 606 <table pgwide="0" frame="none"> 607 <title>Indexed Image Format</title> 608 <tgroup cols="37" align="center"> 609 <colspec colname="id" align="left" /> 610 <colspec colname="fourcc" /> 611 <colspec colname="bit" /> 612 613 <colspec colnum="4" colname="b07" align="center" /> 614 <colspec colnum="5" colname="b06" align="center" /> 615 <colspec colnum="6" colname="b05" align="center" /> 616 <colspec colnum="7" colname="b04" align="center" /> 617 <colspec colnum="8" colname="b03" align="center" /> 618 <colspec colnum="9" colname="b02" align="center" /> 619 <colspec colnum="10" colname="b01" align="center" /> 620 <colspec colnum="11" colname="b00" align="center" /> 621 622 <spanspec namest="b07" nameend="b00" spanname="b0" /> 623 <spanspec namest="b17" nameend="b10" spanname="b1" /> 624 <spanspec namest="b27" nameend="b20" spanname="b2" /> 625 <spanspec namest="b37" nameend="b30" spanname="b3" /> 626 <thead> 627 <row> 628 <entry>Identifier</entry> 629 <entry>Code</entry> 630 <entry> </entry> 631 <entry spanname="b0">Byte 0</entry> 632 </row> 633 <row> 634 <entry> </entry> 635 <entry> </entry> 636 <entry>Bit</entry> 637 <entry>7</entry> 638 <entry>6</entry> 639 <entry>5</entry> 640 <entry>4</entry> 641 <entry>3</entry> 642 <entry>2</entry> 643 <entry>1</entry> 644 <entry>0</entry> 645 </row> 646 </thead> 647 <tbody valign="top"> 648 <row id="V4L2-PIX-FMT-PAL8"> 649 <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry> 650 <entry>'PAL8'</entry> 651 <entry></entry> 652 <entry>i<subscript>7</subscript></entry> 653 <entry>i<subscript>6</subscript></entry> 654 <entry>i<subscript>5</subscript></entry> 655 <entry>i<subscript>4</subscript></entry> 656 <entry>i<subscript>3</subscript></entry> 657 <entry>i<subscript>2</subscript></entry> 658 <entry>i<subscript>1</subscript></entry> 659 <entry>i<subscript>0</subscript></entry> 660 </row> 661 </tbody> 662 </tgroup> 663 </table> 664 </section> 665 666 <section id="pixfmt-rgb"> 667 <title>RGB Formats</title> 668 669 &sub-packed-rgb; 670 &sub-sbggr8; 671 &sub-sgbrg8; 672 &sub-sgrbg8; 673 &sub-srggb8; 674 &sub-sbggr16; 675 &sub-srggb10; 676 &sub-srggb12; 677 </section> 678 679 <section id="yuv-formats"> 680 <title>YUV Formats</title> 681 682 <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> 696 697 &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> 719 720 <section> 721 <title>Compressed Formats</title> 722 723 <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 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 </tbody> 749 </tgroup> 750 </table> 751 </section> 752 753 <section id="pixfmt-reserved"> 754 <title>Reserved Format Identifiers</title> 755 756 <para>These formats are not defined by this specification, they 757 are just listed for reference and to avoid naming conflicts. If you 758 want to register your own format, send an e-mail to the linux-media mailing 759 list &v4l-ml; for inclusion in the <filename>videodev2.h</filename> 760 file. If you want to share your format with other developers add a 761 link to your documentation and send a copy to the linux-media mailing list 762 for inclusion in this section. If you think your format should be listed 763 in a standard format section please make a proposal on the linux-media mailing 764 list.</para> 765 766 <table pgwide="1" frame="none" id="reserved-formats"> 767 <title>Reserved Image Formats</title> 768 <tgroup cols="3" align="left"> 769 &cs-def; 770 <thead> 771 <row> 772 <entry>Identifier</entry> 773 <entry>Code</entry> 774 <entry>Details</entry> 775 </row> 776 </thead> 777 <tbody valign="top"> 778 <row id="V4L2-PIX-FMT-DV"> 779 <entry><constant>V4L2_PIX_FMT_DV</constant></entry> 780 <entry>'dvsd'</entry> 781 <entry>unknown</entry> 782 </row> 783 <row id="V4L2-PIX-FMT-ET61X251"> 784 <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry> 785 <entry>'E625'</entry> 786 <entry>Compressed format of the ET61X251 driver.</entry> 787 </row> 788 <row id="V4L2-PIX-FMT-HI240"> 789 <entry><constant>V4L2_PIX_FMT_HI240</constant></entry> 790 <entry>'HI24'</entry> 791 <entry><para>8 bit RGB format used by the BTTV driver.</para></entry> 792 </row> 793 <row id="V4L2-PIX-FMT-HM12"> 794 <entry><constant>V4L2_PIX_FMT_HM12</constant></entry> 795 <entry>'HM12'</entry> 796 <entry><para>YUV 4:2:0 format used by the 797 IVTV driver, <ulink url="http://www.ivtvdriver.org/"> 798 http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the 799 kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename> 800 </para></entry> 801 </row> 802 <row id="V4L2-PIX-FMT-CPIA1"> 803 <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry> 804 <entry>'CPIA'</entry> 805 <entry>YUV format used by the gspca cpia1 driver.</entry> 806 </row> 807 <row id="V4L2-PIX-FMT-SPCA501"> 808 <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry> 809 <entry>'S501'</entry> 810 <entry>YUYV per line used by the gspca driver.</entry> 811 </row> 812 <row id="V4L2-PIX-FMT-SPCA505"> 813 <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry> 814 <entry>'S505'</entry> 815 <entry>YYUV per line used by the gspca driver.</entry> 816 </row> 817 <row id="V4L2-PIX-FMT-SPCA508"> 818 <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry> 819 <entry>'S508'</entry> 820 <entry>YUVY per line used by the gspca driver.</entry> 821 </row> 822 <row id="V4L2-PIX-FMT-SPCA561"> 823 <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry> 824 <entry>'S561'</entry> 825 <entry>Compressed GBRG Bayer format used by the gspca driver.</entry> 826 </row> 827 <row id="V4L2-PIX-FMT-SGRBG10DPCM8"> 828 <entry><constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant></entry> 829 <entry>'DB10'</entry> 830 <entry>10 bit raw Bayer DPCM compressed to 8 bits.</entry> 831 </row> 832 <row id="V4L2-PIX-FMT-PAC207"> 833 <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry> 834 <entry>'P207'</entry> 835 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 836 </row> 837 <row id="V4L2-PIX-FMT-MR97310A"> 838 <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry> 839 <entry>'M310'</entry> 840 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 841 </row> 842 <row id="V4L2-PIX-FMT-OV511"> 843 <entry><constant>V4L2_PIX_FMT_OV511</constant></entry> 844 <entry>'O511'</entry> 845 <entry>OV511 JPEG format used by the gspca driver.</entry> 846 </row> 847 <row id="V4L2-PIX-FMT-OV518"> 848 <entry><constant>V4L2_PIX_FMT_OV518</constant></entry> 849 <entry>'O518'</entry> 850 <entry>OV518 JPEG format used by the gspca driver.</entry> 851 </row> 852 <row id="V4L2-PIX-FMT-PJPG"> 853 <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry> 854 <entry>'PJPG'</entry> 855 <entry>Pixart 73xx JPEG format used by the gspca driver.</entry> 856 </row> 857 <row id="V4L2-PIX-FMT-SQ905C"> 858 <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry> 859 <entry>'905C'</entry> 860 <entry>Compressed RGGB bayer format used by the gspca driver.</entry> 861 </row> 862 <row id="V4L2-PIX-FMT-MJPEG"> 863 <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry> 864 <entry>'MJPG'</entry> 865 <entry>Compressed format used by the Zoran driver</entry> 866 </row> 867 <row id="V4L2-PIX-FMT-PWC1"> 868 <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry> 869 <entry>'PWC1'</entry> 870 <entry>Compressed format of the PWC driver.</entry> 871 </row> 872 <row id="V4L2-PIX-FMT-PWC2"> 873 <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry> 874 <entry>'PWC2'</entry> 875 <entry>Compressed format of the PWC driver.</entry> 876 </row> 877 <row id="V4L2-PIX-FMT-SN9C10X"> 878 <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry> 879 <entry>'S910'</entry> 880 <entry>Compressed format of the SN9C102 driver.</entry> 881 </row> 882 <row id="V4L2-PIX-FMT-SN9C20X-I420"> 883 <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry> 884 <entry>'S920'</entry> 885 <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry> 886 </row> 887 <row id="V4L2-PIX-FMT-SN9C2028"> 888 <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry> 889 <entry>'SONX'</entry> 890 <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry> 891 </row> 892 <row id="V4L2-PIX-FMT-STV0680"> 893 <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry> 894 <entry>'S680'</entry> 895 <entry>Bayer format of the gspca stv0680 driver.</entry> 896 </row> 897 <row id="V4L2-PIX-FMT-WNVA"> 898 <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry> 899 <entry>'WNVA'</entry> 900 <entry><para>Used by the Winnov Videum driver, <ulink 901 url="http://www.thedirks.org/winnov/"> 902 http://www.thedirks.org/winnov/</ulink></para></entry> 903 </row> 904 <row id="V4L2-PIX-FMT-TM6000"> 905 <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry> 906 <entry>'TM60'</entry> 907 <entry><para>Used by Trident tm6000</para></entry> 908 </row> 909 <row id="V4L2-PIX-FMT-CIT-YYVYUY"> 910 <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry> 911 <entry>'CITV'</entry> 912 <entry><para>Used by xirlink CIT, found at IBM webcams.</para> 913 <para>Uses one line of Y then 1 line of VYUY</para> 914 </entry> 915 </row> 916 <row id="V4L2-PIX-FMT-KONICA420"> 917 <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry> 918 <entry>'KONI'</entry> 919 <entry><para>Used by Konica webcams.</para> 920 <para>YUV420 planar in blocks of 256 pixels.</para> 921 </entry> 922 </row> 923 <row id="V4L2-PIX-FMT-YYUV"> 924 <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry> 925 <entry>'YYUV'</entry> 926 <entry>unknown</entry> 927 </row> 928 <row id="V4L2-PIX-FMT-Y4"> 929 <entry><constant>V4L2_PIX_FMT_Y4</constant></entry> 930 <entry>'Y04 '</entry> 931 <entry>Old 4-bit greyscale format. Only the least significant 4 bits of each byte are used, 932 the other bits are set to 0.</entry> 933 </row> 934 <row id="V4L2-PIX-FMT-Y6"> 935 <entry><constant>V4L2_PIX_FMT_Y6</constant></entry> 936 <entry>'Y06 '</entry> 937 <entry>Old 6-bit greyscale format. Only the least significant 6 bits of each byte are used, 938 the other bits are set to 0.</entry> 939 </row> 940 </tbody> 941 </tgroup> 942 </table> 943 </section> 944 945 <!-- 946 Local Variables: 947 mode: sgml 948 sgml-parent-document: "v4l2.sgml" 949 indent-tabs-mode: nil 950 End: 951 -->
