1 <title>Image Formats</title> 2 3 <para>The V4L2 API was primarily designed for devices exchanging 4image data with applications. The 5<structname>v4l2_pix_format</structname> structure defines the format 6and layout of an image in memory. Image formats are negotiated with 7the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video 8capturing and output, for overlay frame buffer formats see also 9&VIDIOC-G-FBUF;.)</para> 10 11 <table pgwide="1" frame="none" id="v4l2-pix-format"> 12 <title>struct <structname>v4l2_pix_format</structname></title> 13 <tgroup cols="3"> 14 &cs-str; 15 <tbody valign="top"> 16 <row> 17 <entry>__u32</entry> 18 <entry><structfield>width</structfield></entry> 19 <entry>Image width in pixels.</entry> 20 </row> 21 <row> 22 <entry>__u32</entry> 23 <entry><structfield>height</structfield></entry> 24 <entry>Image height in pixels.</entry> 25 </row> 26 <row> 27 <entry spanname="hspan">Applications set these fields to 28request an image size, drivers return the closest possible values. In 29case of planar formats the <structfield>width</structfield> and 30<structfield>height</structfield> applies to the largest plane. To 31avoid ambiguities drivers must return values rounded up to a multiple 32of the scale factor of any smaller planes. For example when the image 33format is YUV 4:2:0, <structfield>width</structfield> and 34<structfield>height</structfield> must be multiples of two.</entry> 35 </row> 36 <row> 37 <entry>__u32</entry> 38 <entry><structfield>pixelformat</structfield></entry> 39 <entry>The pixel format or type of compression, set by the 40application. This is a little endian <link 41linkend="v4l2-fourcc">four character code</link>. V4L2 defines 42standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref 43linkend="yuv-formats" />, and reserved codes in <xref 44linkend="reserved-formats" /></entry> 45 </row> 46 <row> 47 <entry>&v4l2-field;</entry> 48 <entry><structfield>field</structfield></entry> 49 <entry>Video images are typically interlaced. Applications 50can request to capture or output only the top or bottom field, or both 51fields interlaced or sequentially stored in one buffer or alternating 52in separate buffers. Drivers return the actual field order selected. 53For details see <xref linkend="field-order" />.</entry> 54 </row> 55 <row> 56 <entry>__u32</entry> 57 <entry><structfield>bytesperline</structfield></entry> 58 <entry>Distance in bytes between the leftmost pixels in two 59adjacent lines.</entry> 60 </row> 61 <row> 62 <entry spanname="hspan"><para>Both applications and drivers 63can set this field to request padding bytes at the end of each line. 64Drivers however may ignore the value requested by the application, 65returning <structfield>width</structfield> times bytes per pixel or a 66larger value required by the hardware. That implies applications can 67just set this field to zero to get a reasonable 68default.</para><para>Video hardware may access padding bytes, 69therefore they must reside in accessible memory. Consider cases where 70padding bytes after the last line of an image cross a system page 71boundary. Input devices may write padding bytes, the value is 72undefined. Output devices ignore the contents of padding 73bytes.</para><para>When the image format is planar the 74<structfield>bytesperline</structfield> value applies to the largest 75plane and is divided by the same factor as the 76<structfield>width</structfield> field for any smaller planes. For 77example the Cb and Cr planes of a YUV 4:2:0 image have half as many 78padding bytes following each line as the Y plane. To avoid ambiguities 79drivers must return a <structfield>bytesperline</structfield> value 80rounded up to a multiple of the scale factor.</para></entry> 81 </row> 82 <row> 83 <entry>__u32</entry> 84 <entry><structfield>sizeimage</structfield></entry> 85 <entry>Size in bytes of the buffer to hold a complete image, 86set by the driver. Usually this is 87<structfield>bytesperline</structfield> times 88<structfield>height</structfield>. When the image consists of variable 89length compressed data this is the maximum number of bytes required to 90hold an image.</entry> 91 </row> 92 <row> 93 <entry>&v4l2-colorspace;</entry> 94 <entry><structfield>colorspace</structfield></entry> 95 <entry>This information supplements the 96<structfield>pixelformat</structfield> and must be set by the driver, 97see <xref linkend="colorspaces" />.</entry> 98 </row> 99 <row> 100 <entry>__u32</entry> 101 <entry><structfield>priv</structfield></entry> 102 <entry>Reserved for custom (driver defined) additional 103information about formats. When not used drivers and applications must 104set this field to zero.</entry> 105 </row> 106 </tbody> 107 </tgroup> 108 </table> 109 110 <section> 111 <title>Standard Image Formats</title> 112 113 <para>In order to exchange images between drivers and 114applications, it is necessary to have standard image data formats 115which both sides will interpret the same way. V4L2 includes several 116such formats, and this section is intended to be an unambiguous 117specification of the standard image data formats in V4L2.</para> 118 119 <para>V4L2 drivers are not limited to these formats, however. 120Driver-specific formats are possible. In that case the application may 121depend on a codec to convert images to one of the standard formats 122when needed. But the data can still be stored and retrieved in the 123proprietary format. For example, a device may support a proprietary 124compressed format. Applications can still capture and save the data in 125the compressed format, saving much disk space, and later use a codec 126to convert the images to the X Windows screen format when the video is 127to be displayed.</para> 128 129 <para>Even so, ultimately, some standard formats are needed, so 130the V4L2 specification would not be complete without well-defined 131standard formats.</para> 132 133 <para>The V4L2 standard formats are mainly uncompressed formats. The 134pixels are always arranged in memory from left to right, and from top 135to bottom. The first byte of data in the image buffer is always for 136the leftmost pixel of the topmost row. Following that is the pixel 137immediately to its right, and so on until the end of the top row of 138pixels. Following the rightmost pixel of the row there may be zero or 139more bytes of padding to guarantee that each row of pixel data has a 140certain alignment. Following the pad bytes, if any, is data for the 141leftmost pixel of the second row from the top, and so on. The last row 142has just as many pad bytes after it as the other rows.</para> 143 144 <para>In V4L2 each format has an identifier which looks like 145<constant>PIX_FMT_XXX</constant>, defined in the <link 146linkend="videodev">videodev.h</link> header file. These identifiers 147represent <link linkend="v4l2-fourcc">four character codes</link> 148which are also listed below, however they are not the same as those 149used in the Windows world.</para> 150 </section> 151 152 <section id="colorspaces"> 153 <title>Colorspaces</title> 154 155 <para>[intro]</para> 156 157 <!-- See proposal by Billy Biggs, video4linux-list@redhat.com 158on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and 159http://vektor.theorem.ca/graphics/ycbcr/ and 160http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html --> 161 162 <para> 163 <variablelist> 164 <varlistentry> 165 <term>Gamma Correction</term> 166 <listitem> 167 <para>[to do]</para> 168 <para>E'<subscript>R</subscript> = f(R)</para> 169 <para>E'<subscript>G</subscript> = f(G)</para> 170 <para>E'<subscript>B</subscript> = f(B)</para> 171 </listitem> 172 </varlistentry> 173 <varlistentry> 174 <term>Construction of luminance and color-difference 175signals</term> 176 <listitem> 177 <para>[to do]</para> 178 <para>E'<subscript>Y</subscript> = 179Coeff<subscript>R</subscript> E'<subscript>R</subscript> 180+ Coeff<subscript>G</subscript> E'<subscript>G</subscript> 181+ Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> 182 <para>(E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = E'<subscript>R</subscript> 183- Coeff<subscript>R</subscript> E'<subscript>R</subscript> 184- Coeff<subscript>G</subscript> E'<subscript>G</subscript> 185- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> 186 <para>(E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = E'<subscript>B</subscript> 187- Coeff<subscript>R</subscript> E'<subscript>R</subscript> 188- Coeff<subscript>G</subscript> E'<subscript>G</subscript> 189- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> 190 </listitem> 191 </varlistentry> 192 <varlistentry> 193 <term>Re-normalized color-difference signals</term> 194 <listitem> 195 <para>The color-difference signals are scaled back to unity 196range [-0.5;+0.5]:</para> 197 <para>K<subscript>B</subscript> = 0.5 / (1 - Coeff<subscript>B</subscript>)</para> 198 <para>K<subscript>R</subscript> = 0.5 / (1 - Coeff<subscript>R</subscript>)</para> 199 <para>P<subscript>B</subscript> = 200K<subscript>B</subscript> (E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = 201 0.5 (Coeff<subscript>R</subscript> / Coeff<subscript>B</subscript>) E'<subscript>R</subscript> 202+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>B</subscript>) E'<subscript>G</subscript> 203+ 0.5 E'<subscript>B</subscript></para> 204 <para>P<subscript>R</subscript> = 205K<subscript>R</subscript> (E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = 206 0.5 E'<subscript>R</subscript> 207+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>R</subscript>) E'<subscript>G</subscript> 208+ 0.5 (Coeff<subscript>B</subscript> / Coeff<subscript>R</subscript>) E'<subscript>B</subscript></para> 209 </listitem> 210 </varlistentry> 211 <varlistentry> 212 <term>Quantization</term> 213 <listitem> 214 <para>[to do]</para> 215 <para>Y' = (Lum. Levels - 1) · E'<subscript>Y</subscript> + Lum. Offset</para> 216 <para>C<subscript>B</subscript> = (Chrom. Levels - 1) 217· P<subscript>B</subscript> + Chrom. Offset</para> 218 <para>C<subscript>R</subscript> = (Chrom. Levels - 1) 219· P<subscript>R</subscript> + Chrom. Offset</para> 220 <para>Rounding to the nearest integer and clamping to the range 221[0;255] finally yields the digital color components Y'CbCr 222stored in YUV images.</para> 223 </listitem> 224 </varlistentry> 225 </variablelist> 226 </para> 227 228 <example> 229 <title>ITU-R Rec. BT.601 color conversion</title> 230 231 <para>Forward Transformation</para> 232 233 <programlisting> 234int ER, EG, EB; /* gamma corrected RGB input [0;255] */ 235int Y1, Cb, Cr; /* output [0;255] */ 236 237double r, g, b; /* temporaries */ 238double y1, pb, pr; 239 240int 241clamp (double x) 242{ 243 int r = x; /* round to nearest */ 244 245 if (r < 0) return 0; 246 else if (r > 255) return 255; 247 else return r; 248} 249 250r = ER / 255.0; 251g = EG / 255.0; 252b = EB / 255.0; 253 254y1 = 0.299 * r + 0.587 * g + 0.114 * b; 255pb = -0.169 * r - 0.331 * g + 0.5 * b; 256pr = 0.5 * r - 0.419 * g - 0.081 * b; 257 258Y1 = clamp (219 * y1 + 16); 259Cb = clamp (224 * pb + 128); 260Cr = clamp (224 * pr + 128); 261 262/* or shorter */ 263 264y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB; 265 266Y1 = clamp ( (219 / 255.0) * y1 + 16); 267Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128); 268Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128); 269 </programlisting> 270 271 <para>Inverse Transformation</para> 272 273 <programlisting> 274int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */ 275int ER, EG, EB; /* output [0;255] */ 276 277double r, g, b; /* temporaries */ 278double y1, pb, pr; 279 280int 281clamp (double x) 282{ 283 int r = x; /* round to nearest */ 284 285 if (r < 0) return 0; 286 else if (r > 255) return 255; 287 else return r; 288} 289 290y1 = (255 / 219.0) * (Y1 - 16); 291pb = (255 / 224.0) * (Cb - 128); 292pr = (255 / 224.0) * (Cr - 128); 293 294r = 1.0 * y1 + 0 * pb + 1.402 * pr; 295g = 1.0 * y1 - 0.344 * pb - 0.714 * pr; 296b = 1.0 * y1 + 1.772 * pb + 0 * pr; 297 298ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */ 299EG = clamp (g * 255); 300EB = clamp (b * 255); 301 </programlisting> 302 </example> 303 304 <table pgwide="1" id="v4l2-colorspace" orient="land"> 305 <title>enum v4l2_colorspace</title> 306 <tgroup cols="11" align="center"> 307 <colspec align="left" /> 308 <colspec align="center" /> 309 <colspec align="left" /> 310 <colspec colname="cr" /> 311 <colspec colname="cg" /> 312 <colspec colname="cb" /> 313 <colspec colname="wp" /> 314 <colspec colname="gc" /> 315 <colspec colname="lum" /> 316 <colspec colname="qy" /> 317 <colspec colname="qc" /> 318 <spanspec namest="cr" nameend="cb" spanname="chrom" /> 319 <spanspec namest="qy" nameend="qc" spanname="quant" /> 320 <spanspec namest="lum" nameend="qc" spanname="spam" /> 321 <thead> 322 <row> 323 <entry morerows="1">Identifier</entry> 324 <entry morerows="1">Value</entry> 325 <entry morerows="1">Description</entry> 326 <entry spanname="chrom">Chromaticities<footnote> 327 <para>The coordinates of the color primaries are 328given in the CIE system (1931)</para> 329 </footnote></entry> 330 <entry morerows="1">White Point</entry> 331 <entry morerows="1">Gamma Correction</entry> 332 <entry morerows="1">Luminance E'<subscript>Y</subscript></entry> 333 <entry spanname="quant">Quantization</entry> 334 </row> 335 <row> 336 <entry>Red</entry> 337 <entry>Green</entry> 338 <entry>Blue</entry> 339 <entry>Y'</entry> 340 <entry>Cb, Cr</entry> 341 </row> 342 </thead> 343 <tbody valign="top"> 344 <row> 345 <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry> 346 <entry>1</entry> 347 <entry>NTSC/PAL according to <xref linkend="smpte170m" />, 348<xref linkend="itu601" /></entry> 349 <entry>x = 0.630, y = 0.340</entry> 350 <entry>x = 0.310, y = 0.595</entry> 351 <entry>x = 0.155, y = 0.070</entry> 352 <entry>x = 0.3127, y = 0.3290, 353 Illuminant D<subscript>65</subscript></entry> 354 <entry>E' = 4.5 I for I ≤0.018, 3551.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> 356 <entry>0.299 E'<subscript>R</subscript> 357+ 0.587 E'<subscript>G</subscript> 358+ 0.114 E'<subscript>B</subscript></entry> 359 <entry>219 E'<subscript>Y</subscript> + 16</entry> 360 <entry>224 P<subscript>B,R</subscript> + 128</entry> 361 </row> 362 <row> 363 <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry> 364 <entry>2</entry> 365 <entry>1125-Line (US) HDTV, see <xref 366linkend="smpte240m" /></entry> 367 <entry>x = 0.630, y = 0.340</entry> 368 <entry>x = 0.310, y = 0.595</entry> 369 <entry>x = 0.155, y = 0.070</entry> 370 <entry>x = 0.3127, y = 0.3290, 371 Illuminant D<subscript>65</subscript></entry> 372 <entry>E' = 4 I for I ≤0.0228, 3731.1115 I<superscript>0.45</superscript> - 0.1115 for 0.0228 < I</entry> 374 <entry>0.212 E'<subscript>R</subscript> 375+ 0.701 E'<subscript>G</subscript> 376+ 0.087 E'<subscript>B</subscript></entry> 377 <entry>219 E'<subscript>Y</subscript> + 16</entry> 378 <entry>224 P<subscript>B,R</subscript> + 128</entry> 379 </row> 380 <row> 381 <entry><constant>V4L2_COLORSPACE_REC709</constant></entry> 382 <entry>3</entry> 383 <entry>HDTV and modern devices, see <xref 384linkend="itu709" /></entry> 385 <entry>x = 0.640, y = 0.330</entry> 386 <entry>x = 0.300, y = 0.600</entry> 387 <entry>x = 0.150, y = 0.060</entry> 388 <entry>x = 0.3127, y = 0.3290, 389 Illuminant D<subscript>65</subscript></entry> 390 <entry>E' = 4.5 I for I ≤0.018, 3911.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> 392 <entry>0.2125 E'<subscript>R</subscript> 393+ 0.7154 E'<subscript>G</subscript> 394+ 0.0721 E'<subscript>B</subscript></entry> 395 <entry>219 E'<subscript>Y</subscript> + 16</entry> 396 <entry>224 P<subscript>B,R</subscript> + 128</entry> 397 </row> 398 <row> 399 <entry><constant>V4L2_COLORSPACE_BT878</constant></entry> 400 <entry>4</entry> 401 <entry>Broken Bt878 extents<footnote> 402 <para>The ubiquitous Bt878 video capture chip 403quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range 404of Y' = 16 … 253, unlike Rec. 601 Y' = 16 … 405235. This is not a typo in the Bt878 documentation, it has been 406implemented in silicon. The chroma extents are unclear.</para> 407 </footnote>, <xref linkend="itu601" /></entry> 408 <entry>?</entry> 409 <entry>?</entry> 410 <entry>?</entry> 411 <entry>?</entry> 412 <entry>?</entry> 413 <entry>0.299 E'<subscript>R</subscript> 414+ 0.587 E'<subscript>G</subscript> 415+ 0.114 E'<subscript>B</subscript></entry> 416 <entry><emphasis>237</emphasis> E'<subscript>Y</subscript> + 16</entry> 417 <entry>224 P<subscript>B,R</subscript> + 128 (probably)</entry> 418 </row> 419 <row> 420 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry> 421 <entry>5</entry> 422 <entry>M/NTSC<footnote> 423 <para>No identifier exists for M/PAL which uses 424the chromaticities of M/NTSC, the remaining parameters are equal to B and 425G/PAL.</para> 426 </footnote> according to <xref linkend="itu470" />, <xref 427 linkend="itu601" /></entry> 428 <entry>x = 0.67, y = 0.33</entry> 429 <entry>x = 0.21, y = 0.71</entry> 430 <entry>x = 0.14, y = 0.08</entry> 431 <entry>x = 0.310, y = 0.316, Illuminant C</entry> 432 <entry>?</entry> 433 <entry>0.299 E'<subscript>R</subscript> 434+ 0.587 E'<subscript>G</subscript> 435+ 0.114 E'<subscript>B</subscript></entry> 436 <entry>219 E'<subscript>Y</subscript> + 16</entry> 437 <entry>224 P<subscript>B,R</subscript> + 128</entry> 438 </row> 439 <row> 440 <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry> 441 <entry>6</entry> 442 <entry>625-line PAL and SECAM systems according to <xref 443linkend="itu470" />, <xref linkend="itu601" /></entry> 444 <entry>x = 0.64, y = 0.33</entry> 445 <entry>x = 0.29, y = 0.60</entry> 446 <entry>x = 0.15, y = 0.06</entry> 447 <entry>x = 0.313, y = 0.329, 448Illuminant D<subscript>65</subscript></entry> 449 <entry>?</entry> 450 <entry>0.299 E'<subscript>R</subscript> 451+ 0.587 E'<subscript>G</subscript> 452+ 0.114 E'<subscript>B</subscript></entry> 453 <entry>219 E'<subscript>Y</subscript> + 16</entry> 454 <entry>224 P<subscript>B,R</subscript> + 128</entry> 455 </row> 456 <row> 457 <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry> 458 <entry>7</entry> 459 <entry>JPEG Y'CbCr, see <xref linkend="jfif" />, <xref linkend="itu601" /></entry> 460 <entry>?</entry> 461 <entry>?</entry> 462 <entry>?</entry> 463 <entry>?</entry> 464 <entry>?</entry> 465 <entry>0.299 E'<subscript>R</subscript> 466+ 0.587 E'<subscript>G</subscript> 467+ 0.114 E'<subscript>B</subscript></entry> 468 <entry>256 E'<subscript>Y</subscript> + 16<footnote> 469 <para>Note JFIF quantizes 470Y'P<subscript>B</subscript>P<subscript>R</subscript> in range [0;+1] and 471[-0.5;+0.5] to <emphasis>257</emphasis> levels, however Y'CbCr signals 472are still clamped to [0;255].</para> 473 </footnote></entry> 474 <entry>256 P<subscript>B,R</subscript> + 128</entry> 475 </row> 476 <row> 477 <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry> 478 <entry>8</entry> 479 <entry>[?]</entry> 480 <entry>x = 0.640, y = 0.330</entry> 481 <entry>x = 0.300, y = 0.600</entry> 482 <entry>x = 0.150, y = 0.060</entry> 483 <entry>x = 0.3127, y = 0.3290, 484 Illuminant D<subscript>65</subscript></entry> 485 <entry>E' = 4.5 I for I ≤0.018, 4861.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> 487 <entry spanname="spam">n/a</entry> 488 </row> 489 </tbody> 490 </tgroup> 491 </table> 492 </section> 493 494 <section id="pixfmt-indexed"> 495 <title>Indexed Format</title> 496 497 <para>In this format each pixel is represented by an 8 bit index 498into a 256 entry ARGB palette. It is intended for <link 499linkend="osd">Video Output Overlays</link> only. There are no ioctls to 500access the palette, this must be done with ioctls of the Linux framebuffer API.</para> 501 502 <table pgwide="0" frame="none"> 503 <title>Indexed Image Format</title> 504 <tgroup cols="37" align="center"> 505 <colspec colname="id" align="left" /> 506 <colspec colname="fourcc" /> 507 <colspec colname="bit" /> 508 509 <colspec colnum="4" colname="b07" align="center" /> 510 <colspec colnum="5" colname="b06" align="center" /> 511 <colspec colnum="6" colname="b05" align="center" /> 512 <colspec colnum="7" colname="b04" align="center" /> 513 <colspec colnum="8" colname="b03" align="center" /> 514 <colspec colnum="9" colname="b02" align="center" /> 515 <colspec colnum="10" colname="b01" align="center" /> 516 <colspec colnum="11" colname="b00" align="center" /> 517 518 <spanspec namest="b07" nameend="b00" spanname="b0" /> 519 <spanspec namest="b17" nameend="b10" spanname="b1" /> 520 <spanspec namest="b27" nameend="b20" spanname="b2" /> 521 <spanspec namest="b37" nameend="b30" spanname="b3" /> 522 <thead> 523 <row> 524 <entry>Identifier</entry> 525 <entry>Code</entry> 526 <entry> </entry> 527 <entry spanname="b0">Byte 0</entry> 528 </row> 529 <row> 530 <entry> </entry> 531 <entry> </entry> 532 <entry>Bit</entry> 533 <entry>7</entry> 534 <entry>6</entry> 535 <entry>5</entry> 536 <entry>4</entry> 537 <entry>3</entry> 538 <entry>2</entry> 539 <entry>1</entry> 540 <entry>0</entry> 541 </row> 542 </thead> 543 <tbody valign="top"> 544 <row id="V4L2-PIX-FMT-PAL8"> 545 <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry> 546 <entry>'PAL8'</entry> 547 <entry></entry> 548 <entry>i<subscript>7</subscript></entry> 549 <entry>i<subscript>6</subscript></entry> 550 <entry>i<subscript>5</subscript></entry> 551 <entry>i<subscript>4</subscript></entry> 552 <entry>i<subscript>3</subscript></entry> 553 <entry>i<subscript>2</subscript></entry> 554 <entry>i<subscript>1</subscript></entry> 555 <entry>i<subscript>0</subscript></entry> 556 </row> 557 </tbody> 558 </tgroup> 559 </table> 560 </section> 561 562 <section id="pixfmt-rgb"> 563 <title>RGB Formats</title> 564 565 &sub-packed-rgb; 566 &sub-sbggr8; 567 &sub-sgbrg8; 568 &sub-sgrbg8; 569 &sub-sbggr16; 570 </section> 571 572 <section id="yuv-formats"> 573 <title>YUV Formats</title> 574 575 <para>YUV is the format native to TV broadcast and composite video 576signals. It separates the brightness information (Y) from the color 577information (U and V or Cb and Cr). The color information consists of 578red and blue <emphasis>color difference</emphasis> signals, this way 579the green component can be reconstructed by subtracting from the 580brightness component. See <xref linkend="colorspaces" /> for conversion 581examples. YUV was chosen because early television would only transmit 582brightness information. To add color in a way compatible with existing 583receivers a new signal carrier was added to transmit the color 584difference signals. Secondary in the YUV format the U and V components 585usually have lower resolution than the Y component. This is an analog 586video compression technique taking advantage of a property of the 587human visual system, being more sensitive to brightness 588information.</para> 589 590 &sub-packed-yuv; 591 &sub-grey; 592 &sub-y16; 593 &sub-yuyv; 594 &sub-uyvy; 595 &sub-yvyu; 596 &sub-vyuy; 597 &sub-y41p; 598 &sub-yuv420; 599 &sub-yuv410; 600 &sub-yuv422p; 601 &sub-yuv411p; 602 &sub-nv12; 603 &sub-nv16; 604 </section> 605 606 <section> 607 <title>Compressed Formats</title> 608 609 <table pgwide="1" frame="none" id="compressed-formats"> 610 <title>Compressed Image Formats</title> 611 <tgroup cols="3" align="left"> 612 &cs-def; 613 <thead> 614 <row> 615 <entry>Identifier</entry> 616 <entry>Code</entry> 617 <entry>Details</entry> 618 </row> 619 </thead> 620 <tbody valign="top"> 621 <row id="V4L2-PIX-FMT-JPEG"> 622 <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry> 623 <entry>'JPEG'</entry> 624 <entry>TBD. See also &VIDIOC-G-JPEGCOMP;, 625 &VIDIOC-S-JPEGCOMP;.</entry> 626 </row> 627 <row id="V4L2-PIX-FMT-MPEG"> 628 <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry> 629 <entry>'MPEG'</entry> 630 <entry>MPEG stream. The actual format is determined by 631extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see 632<xref linkend="mpeg-control-id" />.</entry> 633 </row> 634 </tbody> 635 </tgroup> 636 </table> 637 </section> 638 639 <section id="pixfmt-reserved"> 640 <title>Reserved Format Identifiers</title> 641 642 <para>These formats are not defined by this specification, they 643are just listed for reference and to avoid naming conflicts. If you 644want to register your own format, send an e-mail to the linux-media mailing 645list &v4l-ml; for inclusion in the <filename>videodev2.h</filename> 646file. If you want to share your format with other developers add a 647link to your documentation and send a copy to the linux-media mailing list 648for inclusion in this section. If you think your format should be listed 649in a standard format section please make a proposal on the linux-media mailing 650list.</para> 651 652 <table pgwide="1" frame="none" id="reserved-formats"> 653 <title>Reserved Image Formats</title> 654 <tgroup cols="3" align="left"> 655 &cs-def; 656 <thead> 657 <row> 658 <entry>Identifier</entry> 659 <entry>Code</entry> 660 <entry>Details</entry> 661 </row> 662 </thead> 663 <tbody valign="top"> 664 <row id="V4L2-PIX-FMT-DV"> 665 <entry><constant>V4L2_PIX_FMT_DV</constant></entry> 666 <entry>'dvsd'</entry> 667 <entry>unknown</entry> 668 </row> 669 <row id="V4L2-PIX-FMT-ET61X251"> 670 <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry> 671 <entry>'E625'</entry> 672 <entry>Compressed format of the ET61X251 driver.</entry> 673 </row> 674 <row id="V4L2-PIX-FMT-HI240"> 675 <entry><constant>V4L2_PIX_FMT_HI240</constant></entry> 676 <entry>'HI24'</entry> 677 <entry><para>8 bit RGB format used by the BTTV driver.</para></entry> 678 </row> 679 <row id="V4L2-PIX-FMT-HM12"> 680 <entry><constant>V4L2_PIX_FMT_HM12</constant></entry> 681 <entry>'HM12'</entry> 682 <entry><para>YUV 4:2:0 format used by the 683IVTV driver, <ulink url="http://www.ivtvdriver.org/"> 684http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the 685kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename> 686</para></entry> 687 </row> 688 <row id="V4L2-PIX-FMT-SPCA501"> 689 <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry> 690 <entry>'S501'</entry> 691 <entry>YUYV per line used by the gspca driver.</entry> 692 </row> 693 <row id="V4L2-PIX-FMT-SPCA505"> 694 <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry> 695 <entry>'S505'</entry> 696 <entry>YYUV per line used by the gspca driver.</entry> 697 </row> 698 <row id="V4L2-PIX-FMT-SPCA508"> 699 <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry> 700 <entry>'S508'</entry> 701 <entry>YUVY per line used by the gspca driver.</entry> 702 </row> 703 <row id="V4L2-PIX-FMT-SPCA561"> 704 <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry> 705 <entry>'S561'</entry> 706 <entry>Compressed GBRG Bayer format used by the gspca driver.</entry> 707 </row> 708 <row id="V4L2-PIX-FMT-SGRBG10"> 709 <entry><constant>V4L2_PIX_FMT_SGRBG10</constant></entry> 710 <entry>'DA10'</entry> 711 <entry>10 bit raw Bayer, expanded to 16 bits.</entry> 712 </row> 713 <row id="V4L2-PIX-FMT-SGRBG10DPCM8"> 714 <entry><constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant></entry> 715 <entry>'DB10'</entry> 716 <entry>10 bit raw Bayer DPCM compressed to 8 bits.</entry> 717 </row> 718 <row id="V4L2-PIX-FMT-PAC207"> 719 <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry> 720 <entry>'P207'</entry> 721 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 722 </row> 723 <row id="V4L2-PIX-FMT-MR97310A"> 724 <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry> 725 <entry>'M310'</entry> 726 <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> 727 </row> 728 <row id="V4L2-PIX-FMT-OV511"> 729 <entry><constant>V4L2_PIX_FMT_OV511</constant></entry> 730 <entry>'O511'</entry> 731 <entry>OV511 JPEG format used by the gspca driver.</entry> 732 </row> 733 <row id="V4L2-PIX-FMT-OV518"> 734 <entry><constant>V4L2_PIX_FMT_OV518</constant></entry> 735 <entry>'O518'</entry> 736 <entry>OV518 JPEG format used by the gspca driver.</entry> 737 </row> 738 <row id="V4L2-PIX-FMT-PJPG"> 739 <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry> 740 <entry>'PJPG'</entry> 741 <entry>Pixart 73xx JPEG format used by the gspca driver.</entry> 742 </row> 743 <row id="V4L2-PIX-FMT-SQ905C"> 744 <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry> 745 <entry>'905C'</entry> 746 <entry>Compressed RGGB bayer format used by the gspca driver.</entry> 747 </row> 748 <row id="V4L2-PIX-FMT-MJPEG"> 749 <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry> 750 <entry>'MJPG'</entry> 751 <entry>Compressed format used by the Zoran driver</entry> 752 </row> 753 <row id="V4L2-PIX-FMT-PWC1"> 754 <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry> 755 <entry>'PWC1'</entry> 756 <entry>Compressed format of the PWC driver.</entry> 757 </row> 758 <row id="V4L2-PIX-FMT-PWC2"> 759 <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry> 760 <entry>'PWC2'</entry> 761 <entry>Compressed format of the PWC driver.</entry> 762 </row> 763 <row id="V4L2-PIX-FMT-SN9C10X"> 764 <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry> 765 <entry>'S910'</entry> 766 <entry>Compressed format of the SN9C102 driver.</entry> 767 </row> 768 <row id="V4L2-PIX-FMT-SN9C20X-I420"> 769 <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry> 770 <entry>'S920'</entry> 771 <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry> 772 </row> 773 <row id="V4L2-PIX-FMT-STV0680"> 774 <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry> 775 <entry>'S680'</entry> 776 <entry>Bayer format of the gspca stv0680 driver.</entry> 777 </row> 778 <row id="V4L2-PIX-FMT-WNVA"> 779 <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry> 780 <entry>'WNVA'</entry> 781 <entry><para>Used by the Winnov Videum driver, <ulink 782url="http://www.thedirks.org/winnov/"> 783http://www.thedirks.org/winnov/</ulink></para></entry> 784 </row> 785 <row id="V4L2-PIX-FMT-TM6000"> 786 <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry> 787 <entry>'TM60'</entry> 788 <entry><para>Used by Trident tm6000</para></entry> 789 </row> 790 <row id="V4L2-PIX-FMT-YYUV"> 791 <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry> 792 <entry>'YYUV'</entry> 793 <entry>unknown</entry> 794 </row> 795 <row id="V4L2-PIX-FMT-Y4"> 796 <entry><constant>V4L2_PIX_FMT_Y4</constant></entry> 797 <entry>'Y04 '</entry> 798 <entry>Old 4-bit greyscale format. Only the least significant 4 bits of each byte are used, 799the other bits are set to 0.</entry> 800 </row> 801 <row id="V4L2-PIX-FMT-Y6"> 802 <entry><constant>V4L2_PIX_FMT_Y6</constant></entry> 803 <entry>'Y06 '</entry> 804 <entry>Old 6-bit greyscale format. Only the least significant 6 bits of each byte are used, 805the other bits are set to 0.</entry> 806 </row> 807 </tbody> 808 </tgroup> 809 </table> 810 </section> 811 812 <!-- 813Local Variables: 814mode: sgml 815sgml-parent-document: "v4l2.sgml" 816indent-tabs-mode: nil 817End: 818 --> 819