Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <title>Sliced VBI Data Interface</title> 2 3 <para>VBI stands for Vertical Blanking Interval, a gap in the 4 sequence of lines of an analog video signal. During VBI no picture 5 information is transmitted, allowing some time while the electron beam 6 of a cathode ray tube TV returns to the top of the screen.</para> 7 8 <para>Sliced VBI devices use hardware to demodulate data transmitted 9 in the VBI. V4L2 drivers shall <emphasis>not</emphasis> do this by 10 software, see also the <link linkend="raw-vbi">raw VBI 11 interface</link>. The data is passed as short packets of fixed size, 12 covering one scan line each. The number of packets per video frame is 13 variable.</para> 14 15 <para>Sliced VBI capture and output devices are accessed through the 16 same character special files as raw VBI devices. When a driver 17 supports both interfaces, the default function of a 18 <filename>/dev/vbi</filename> device is <emphasis>raw</emphasis> VBI 19 capturing or output, and the sliced VBI function is only available 20 after calling the &VIDIOC-S-FMT; ioctl as defined below. Likewise a 21 <filename>/dev/video</filename> device may support the sliced VBI API, 22 however the default function here is video capturing or output. 23 Different file descriptors must be used to pass raw and sliced VBI 24 data simultaneously, if this is supported by the driver.</para> 25 26 <section> 27 <title>Querying Capabilities</title> 28 29 <para>Devices supporting the sliced VBI capturing or output API 30 set the <constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant> or 31 <constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant> flag respectively, in 32 the <structfield>capabilities</structfield> field of &v4l2-capability; 33 returned by the &VIDIOC-QUERYCAP; ioctl. At least one of the 34 read/write, streaming or asynchronous <link linkend="io">I/O 35 methods</link> must be supported. Sliced VBI devices may have a tuner 36 or modulator.</para> 37 </section> 38 39 <section> 40 <title>Supplemental Functions</title> 41 42 <para>Sliced VBI devices shall support <link linkend="video">video 43 input or output</link> and <link linkend="tuner">tuner or 44 modulator</link> ioctls if they have these capabilities, and they may 45 support <link linkend="control">control</link> ioctls. The <link 46 linkend="standard">video standard</link> ioctls provide information 47 vital to program a sliced VBI device, therefore must be 48 supported.</para> 49 </section> 50 51 <section id="sliced-vbi-format-negotitation"> 52 <title>Sliced VBI Format Negotiation</title> 53 54 <para>To find out which data services are supported by the 55 hardware applications can call the &VIDIOC-G-SLICED-VBI-CAP; ioctl. 56 All drivers implementing the sliced VBI interface must support this 57 ioctl. The results may differ from those of the &VIDIOC-S-FMT; ioctl 58 when the number of VBI lines the hardware can capture or output per 59 frame, or the number of services it can identify on a given line are 60 limited. For example on PAL line 16 the hardware may be able to look 61 for a VPS or Teletext signal, but not both at the same time.</para> 62 63 <para>To determine the currently selected services applications 64 set the <structfield>type </structfield> field of &v4l2-format; to 65 <constant> V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> or <constant> 66 V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant>, and the &VIDIOC-G-FMT; 67 ioctl fills the <structfield>fmt.sliced</structfield> member, a 68 &v4l2-sliced-vbi-format;.</para> 69 70 <para>Applications can request different parameters by 71 initializing or modifying the <structfield>fmt.sliced</structfield> 72 member and calling the &VIDIOC-S-FMT; ioctl with a pointer to the 73 <structname>v4l2_format</structname> structure.</para> 74 75 <para>The sliced VBI API is more complicated than the raw VBI API 76 because the hardware must be told which VBI service to expect on each 77 scan line. Not all services may be supported by the hardware on all 78 lines (this is especially true for VBI output where Teletext is often 79 unsupported and other services can only be inserted in one specific 80 line). In many cases, however, it is sufficient to just set the 81 <structfield>service_set</structfield> field to the required services 82 and let the driver fill the <structfield>service_lines</structfield> 83 array according to hardware capabilities. Only if more precise control 84 is needed should the programmer set the 85 <structfield>service_lines</structfield> array explicitly.</para> 86 87 <para>The &VIDIOC-S-FMT; ioctl modifies the parameters 88 according to hardware capabilities. When the driver allocates 89 resources at this point, it may return an &EBUSY; if the required 90 resources are temporarily unavailable. Other resource allocation 91 points which may return <errorcode>EBUSY</errorcode> can be the 92 &VIDIOC-STREAMON; ioctl and the first &func-read;, &func-write; and 93 &func-select; call.</para> 94 95 <table frame="none" pgwide="1" id="v4l2-sliced-vbi-format"> 96 <title>struct 97 <structname>v4l2_sliced_vbi_format</structname></title> 98 <tgroup cols="5"> 99 <colspec colname="c1" colwidth="3*" /> 100 <colspec colname="c2" colwidth="3*" /> 101 <colspec colname="c3" colwidth="2*" /> 102 <colspec colname="c4" colwidth="2*" /> 103 <colspec colname="c5" colwidth="2*" /> 104 <spanspec namest="c3" nameend="c5" spanname="hspan" /> 105 <tbody valign="top"> 106 <row> 107 <entry>__u32</entry> 108 <entry><structfield>service_set</structfield></entry> 109 <entry spanname="hspan"><para>If 110 <structfield>service_set</structfield> is non-zero when passed with 111 &VIDIOC-S-FMT; or &VIDIOC-TRY-FMT;, the 112 <structfield>service_lines</structfield> array will be filled by the 113 driver according to the services specified in this field. For example, 114 if <structfield>service_set</structfield> is initialized with 115 <constant>V4L2_SLICED_TELETEXT_B | V4L2_SLICED_WSS_625</constant>, a 116 driver for the cx25840 video decoder sets lines 7-22 of both 117 fields<footnote><para>According to <link 118 linkend="ets300706">ETS 300 706</link> lines 6-22 of the 119 first field and lines 5-22 of the second field may carry Teletext 120 data.</para></footnote> to <constant>V4L2_SLICED_TELETEXT_B</constant> 121 and line 23 of the first field to 122 <constant>V4L2_SLICED_WSS_625</constant>. If 123 <structfield>service_set</structfield> is set to zero, then the values 124 of <structfield>service_lines</structfield> will be used instead. 125 </para><para>On return the driver sets this field to the union of all 126 elements of the returned <structfield>service_lines</structfield> 127 array. It may contain less services than requested, perhaps just one, 128 if the hardware cannot handle more services simultaneously. It may be 129 empty (zero) if none of the requested services are supported by the 130 hardware.</para></entry> 131 </row> 132 <row> 133 <entry>__u16</entry> 134 <entry><structfield>service_lines</structfield>[2][24]</entry> 135 <entry spanname="hspan"><para>Applications initialize this 136 array with sets of data services the driver shall look for or insert 137 on the respective scan line. Subject to hardware capabilities drivers 138 return the requested set, a subset, which may be just a single 139 service, or an empty set. When the hardware cannot handle multiple 140 services on the same line the driver shall choose one. No assumptions 141 can be made on which service the driver chooses.</para><para>Data 142 services are defined in <xref linkend="vbi-services2" />. Array indices 143 map to ITU-R line numbers (see also <xref linkend="vbi-525" /> and <xref 144 linkend="vbi-625" />) as follows: <!-- No nested 145 tables, sigh. --></para></entry> 146 </row> 147 <row> 148 <entry></entry> 149 <entry></entry> 150 <entry>Element</entry> 151 <entry>525 line systems</entry> 152 <entry>625 line systems</entry> 153 </row> 154 <row> 155 <entry></entry> 156 <entry></entry> 157 <entry><structfield>service_lines</structfield>[0][1]</entry> 158 <entry align="center">1</entry> 159 <entry align="center">1</entry> 160 </row> 161 <row> 162 <entry></entry> 163 <entry></entry> 164 <entry><structfield>service_lines</structfield>[0][23]</entry> 165 <entry align="center">23</entry> 166 <entry align="center">23</entry> 167 </row> 168 <row> 169 <entry></entry> 170 <entry></entry> 171 <entry><structfield>service_lines</structfield>[1][1]</entry> 172 <entry align="center">264</entry> 173 <entry align="center">314</entry> 174 </row> 175 <row> 176 <entry></entry> 177 <entry></entry> 178 <entry><structfield>service_lines</structfield>[1][23]</entry> 179 <entry align="center">286</entry> 180 <entry align="center">336</entry> 181 </row> 182 <!-- End of line numbers table. --> 183 <row> 184 <entry></entry> 185 <entry></entry> 186 <entry spanname="hspan">Drivers must set 187 <structfield>service_lines</structfield>[0][0] and 188 <structfield>service_lines</structfield>[1][0] to zero.</entry> 189 </row> 190 <row> 191 <entry>__u32</entry> 192 <entry><structfield>io_size</structfield></entry> 193 <entry spanname="hspan">Maximum number of bytes passed by 194 one &func-read; or &func-write; call, and the buffer size in bytes for 195 the &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. Drivers set this field to 196 the size of &v4l2-sliced-vbi-data; times the number of non-zero 197 elements in the returned <structfield>service_lines</structfield> 198 array (that is the number of lines potentially carrying data).</entry> 199 </row> 200 <row> 201 <entry>__u32</entry> 202 <entry><structfield>reserved</structfield>[2]</entry> 203 <entry spanname="hspan">This array is reserved for future 204 extensions. Applications and drivers must set it to zero.</entry> 205 </row> 206 </tbody> 207 </tgroup> 208 </table> 209 210 <!-- See also vidioc-g-sliced-vbi-cap.sgml --> 211 <table frame="none" pgwide="1" id="vbi-services2"> 212 <title>Sliced VBI services</title> 213 <tgroup cols="5"> 214 <colspec colname="c1" colwidth="2*" /> 215 <colspec colname="c2" colwidth="1*" /> 216 <colspec colname="c3" colwidth="1*" /> 217 <colspec colname="c4" colwidth="2*" /> 218 <colspec colname="c5" colwidth="2*" /> 219 <spanspec namest="c3" nameend="c5" spanname="rlp" /> 220 <thead> 221 <row> 222 <entry>Symbol</entry> 223 <entry>Value</entry> 224 <entry>Reference</entry> 225 <entry>Lines, usually</entry> 226 <entry>Payload</entry> 227 </row> 228 </thead> 229 <tbody valign="top"> 230 <row> 231 <entry><constant>V4L2_SLICED_TELETEXT_B</constant> 232 (Teletext System B)</entry> 233 <entry>0x0001</entry> 234 <entry><xref linkend="ets300706" />, <xref linkend="itu653" /></entry> 235 <entry>PAL/SECAM line 7-22, 320-335 (second field 7-22)</entry> 236 <entry>Last 42 of the 45 byte Teletext packet, that is 237 without clock run-in and framing code, lsb first transmitted.</entry> 238 </row> 239 <row> 240 <entry><constant>V4L2_SLICED_VPS</constant></entry> 241 <entry>0x0400</entry> 242 <entry><xref linkend="ets300231" /></entry> 243 <entry>PAL line 16</entry> 244 <entry>Byte number 3 to 15 according to Figure 9 of 245 ETS 300 231, lsb first transmitted.</entry> 246 </row> 247 <row> 248 <entry><constant>V4L2_SLICED_CAPTION_525</constant></entry> 249 <entry>0x1000</entry> 250 <entry><xref linkend="eia608" /></entry> 251 <entry>NTSC line 21, 284 (second field 21)</entry> 252 <entry>Two bytes in transmission order, including parity 253 bit, lsb first transmitted.</entry> 254 </row> 255 <row> 256 <entry><constant>V4L2_SLICED_WSS_625</constant></entry> 257 <entry>0x4000</entry> 258 <entry><xref linkend="itu1119" />, <xref linkend="en300294" /></entry> 259 <entry>PAL/SECAM line 23</entry> 260 <entry><screen> 261 Byte 0 1 262 msb lsb msb lsb 263 Bit 7 6 5 4 3 2 1 0 x x 13 12 11 10 9 264 </screen></entry> 265 </row> 266 <row> 267 <entry><constant>V4L2_SLICED_VBI_525</constant></entry> 268 <entry>0x1000</entry> 269 <entry spanname="rlp">Set of services applicable to 525 270 line systems.</entry> 271 </row> 272 <row> 273 <entry><constant>V4L2_SLICED_VBI_625</constant></entry> 274 <entry>0x4401</entry> 275 <entry spanname="rlp">Set of services applicable to 625 276 line systems.</entry> 277 </row> 278 </tbody> 279 </tgroup> 280 </table> 281 282 <para>Drivers may return an &EINVAL; when applications attempt to 283 read or write data without prior format negotiation, after switching 284 the video standard (which may invalidate the negotiated VBI 285 parameters) and after switching the video input (which may change the 286 video standard as a side effect). The &VIDIOC-S-FMT; ioctl may return 287 an &EBUSY; when applications attempt to change the format while i/o is 288 in progress (between a &VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; call, 289 and after the first &func-read; or &func-write; call).</para> 290 </section> 291 292 <section> 293 <title>Reading and writing sliced VBI data</title> 294 295 <para>A single &func-read; or &func-write; call must pass all data 296 belonging to one video frame. That is an array of 297 <structname>v4l2_sliced_vbi_data</structname> structures with one or 298 more elements and a total size not exceeding 299 <structfield>io_size</structfield> bytes. Likewise in streaming I/O 300 mode one buffer of <structfield>io_size</structfield> bytes must 301 contain data of one video frame. The <structfield>id</structfield> of 302 unused <structname>v4l2_sliced_vbi_data</structname> elements must be 303 zero.</para> 304 305 <table frame="none" pgwide="1" id="v4l2-sliced-vbi-data"> 306 <title>struct 307 <structname>v4l2_sliced_vbi_data</structname></title> 308 <tgroup cols="3"> 309 &cs-def; 310 <tbody valign="top"> 311 <row> 312 <entry>__u32</entry> 313 <entry><structfield>id</structfield></entry> 314 <entry>A flag from <xref linkend="vbi-services" /> 315 identifying the type of data in this packet. Only a single bit must be 316 set. When the <structfield>id</structfield> of a captured packet is 317 zero, the packet is empty and the contents of other fields are 318 undefined. Applications shall ignore empty packets. When the 319 <structfield>id</structfield> of a packet for output is zero the 320 contents of the <structfield>data</structfield> field are undefined 321 and the driver must no longer insert data on the requested 322 <structfield>field</structfield> and 323 <structfield>line</structfield>.</entry> 324 </row> 325 <row> 326 <entry>__u32</entry> 327 <entry><structfield>field</structfield></entry> 328 <entry>The video field number this data has been captured 329 from, or shall be inserted at. <constant>0</constant> for the first 330 field, <constant>1</constant> for the second field.</entry> 331 </row> 332 <row> 333 <entry>__u32</entry> 334 <entry><structfield>line</structfield></entry> 335 <entry>The field (as opposed to frame) line number this 336 data has been captured from, or shall be inserted at. See <xref 337 linkend="vbi-525" /> and <xref linkend="vbi-625" /> for valid 338 values. Sliced VBI capture devices can set the line number of all 339 packets to <constant>0</constant> if the hardware cannot reliably 340 identify scan lines. The field number must always be valid.</entry> 341 </row> 342 <row> 343 <entry>__u32</entry> 344 <entry><structfield>reserved</structfield></entry> 345 <entry>This field is reserved for future extensions. 346 Applications and drivers must set it to zero.</entry> 347 </row> 348 <row> 349 <entry>__u8</entry> 350 <entry><structfield>data</structfield>[48]</entry> 351 <entry>The packet payload. See <xref 352 linkend="vbi-services" /> for the contents and number of 353 bytes passed for each data type. The contents of padding bytes at the 354 end of this array are undefined, drivers and applications shall ignore 355 them.</entry> 356 </row> 357 </tbody> 358 </tgroup> 359 </table> 360 361 <para>Packets are always passed in ascending line number order, 362 without duplicate line numbers. The &func-write; function and the 363 &VIDIOC-QBUF; ioctl must return an &EINVAL; when applications violate 364 this rule. They must also return an &EINVAL; when applications pass an 365 incorrect field or line number, or a combination of 366 <structfield>field</structfield>, <structfield>line</structfield> and 367 <structfield>id</structfield> which has not been negotiated with the 368 &VIDIOC-G-FMT; or &VIDIOC-S-FMT; ioctl. When the line numbers are 369 unknown the driver must pass the packets in transmitted order. The 370 driver can insert empty packets with <structfield>id</structfield> set 371 to zero anywhere in the packet array.</para> 372 373 <para>To assure synchronization and to distinguish from frame 374 dropping, when a captured frame does not carry any of the requested 375 data services drivers must pass one or more empty packets. When an 376 application fails to pass VBI data in time for output, the driver 377 must output the last VPS and WSS packet again, and disable the output 378 of Closed Caption and Teletext data, or output data which is ignored 379 by Closed Caption and Teletext decoders.</para> 380 381 <para>A sliced VBI device may support <link 382 linkend="rw">read/write</link> and/or streaming (<link 383 linkend="mmap">memory mapping</link> and/or <link linkend="userp">user 384 pointer</link>) I/O. The latter bears the possibility of synchronizing 385 video and VBI data by using buffer timestamps.</para> 386 387 </section> 388 389 <section> 390 <title>Sliced VBI Data in MPEG Streams</title> 391 392 <para>If a device can produce an MPEG output stream, it may be 393 capable of providing <link 394 linkend="sliced-vbi-format-negotitation">negotiated sliced VBI 395 services</link> as data embedded in the MPEG stream. Users or 396 applications control this sliced VBI data insertion with the <link 397 linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> 398 control.</para> 399 400 <para>If the driver does not provide the <link 401 linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> 402 control, or only allows that control to be set to <link 403 linkend="v4l2-mpeg-stream-vbi-fmt"><constant> 404 V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link>, then the device 405 cannot embed sliced VBI data in the MPEG stream.</para> 406 407 <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"> 408 V4L2_CID_MPEG_STREAM_VBI_FMT</link> control does not implicitly set 409 the device driver to capture nor cease capturing sliced VBI data. The 410 control only indicates to embed sliced VBI data in the MPEG stream, if 411 an application has negotiated sliced VBI service be captured.</para> 412 413 <para>It may also be the case that a device can embed sliced VBI 414 data in only certain types of MPEG streams: for example in an MPEG-2 415 PS but not an MPEG-2 TS. In this situation, if sliced VBI data 416 insertion is requested, the sliced VBI data will be embedded in MPEG 417 stream types when supported, and silently omitted from MPEG stream 418 types where sliced VBI data insertion is not supported by the device. 419 </para> 420 421 <para>The following subsections specify the format of the 422 embedded sliced VBI data.</para> 423 424 <section> 425 <title>MPEG Stream Embedded, Sliced VBI Data Format: NONE</title> 426 <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant> 427 V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link> embedded sliced VBI 428 format shall be interpreted by drivers as a control to cease 429 embedding sliced VBI data in MPEG streams. Neither the device nor 430 driver shall insert "empty" embedded sliced VBI data packets in the 431 MPEG stream when this format is set. No MPEG stream data structures 432 are specified for this format.</para> 433 </section> 434 435 <section> 436 <title>MPEG Stream Embedded, Sliced VBI Data Format: IVTV</title> 437 <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant> 438 V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> embedded sliced VBI 439 format, when supported, indicates to the driver to embed up to 36 440 lines of sliced VBI data per frame in an MPEG-2 <emphasis>Private 441 Stream 1 PES</emphasis> packet encapsulated in an MPEG-2 <emphasis> 442 Program Pack</emphasis> in the MPEG stream.</para> 443 444 <para><emphasis>Historical context</emphasis>: This format 445 specification originates from a custom, embedded, sliced VBI data 446 format used by the <filename>ivtv</filename> driver. This format 447 has already been informally specified in the kernel sources in the 448 file <filename>Documentation/video4linux/cx2341x/README.vbi</filename> 449 . The maximum size of the payload and other aspects of this format 450 are driven by the CX23415 MPEG decoder's capabilities and limitations 451 with respect to extracting, decoding, and displaying sliced VBI data 452 embedded within an MPEG stream.</para> 453 454 <para>This format's use is <emphasis>not</emphasis> exclusive to 455 the <filename>ivtv</filename> driver <emphasis>nor</emphasis> 456 exclusive to CX2341x devices, as the sliced VBI data packet insertion 457 into the MPEG stream is implemented in driver software. At least the 458 <filename>cx18</filename> driver provides sliced VBI data insertion 459 into an MPEG-2 PS in this format as well.</para> 460 461 <para>The following definitions specify the payload of the 462 MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packets that contain 463 sliced VBI data when <link linkend="v4l2-mpeg-stream-vbi-fmt"> 464 <constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> is set. 465 (The MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packet header 466 and encapsulating MPEG-2 <emphasis>Program Pack</emphasis> header are 467 not detailed here. Please refer to the MPEG-2 specifications for 468 details on those packet headers.)</para> 469 470 <para>The payload of the MPEG-2 <emphasis>Private Stream 1 PES 471 </emphasis> packets that contain sliced VBI data is specified by 472 &v4l2-mpeg-vbi-fmt-ivtv;. The payload is variable 473 length, depending on the actual number of lines of sliced VBI data 474 present in a video frame. The payload may be padded at the end with 475 unspecified fill bytes to align the end of the payload to a 4-byte 476 boundary. The payload shall never exceed 1552 bytes (2 fields with 477 18 lines/field with 43 bytes of data/line and a 4 byte magic number). 478 </para> 479 480 <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv"> 481 <title>struct <structname>v4l2_mpeg_vbi_fmt_ivtv</structname> 482 </title> 483 <tgroup cols="4"> 484 &cs-ustr; 485 <tbody valign="top"> 486 <row> 487 <entry>__u8</entry> 488 <entry><structfield>magic</structfield>[4]</entry> 489 <entry></entry> 490 <entry>A "magic" constant from <xref 491 linkend="v4l2-mpeg-vbi-fmt-ivtv-magic" /> that indicates 492 this is a valid sliced VBI data payload and also indicates which 493 member of the anonymous union, <structfield>itv0</structfield> or 494 <structfield>ITV0</structfield>, to use for the payload data.</entry> 495 </row> 496 <row> 497 <entry>union</entry> 498 <entry>(anonymous)</entry> 499 </row> 500 <row> 501 <entry></entry> 502 <entry>struct <link linkend="v4l2-mpeg-vbi-itv0"> 503 <structname>v4l2_mpeg_vbi_itv0</structname></link> 504 </entry> 505 <entry><structfield>itv0</structfield></entry> 506 <entry>The primary form of the sliced VBI data payload 507 that contains anywhere from 1 to 35 lines of sliced VBI data. 508 Line masks are provided in this form of the payload indicating 509 which VBI lines are provided.</entry> 510 </row> 511 <row> 512 <entry></entry> 513 <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-1"> 514 <structname>v4l2_mpeg_vbi_ITV0</structname></link> 515 </entry> 516 <entry><structfield>ITV0</structfield></entry> 517 <entry>An alternate form of the sliced VBI data payload 518 used when 36 lines of sliced VBI data are present. No line masks are 519 provided in this form of the payload; all valid line mask bits are 520 implcitly set.</entry> 521 </row> 522 </tbody> 523 </tgroup> 524 </table> 525 526 <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv-magic"> 527 <title>Magic Constants for &v4l2-mpeg-vbi-fmt-ivtv; 528 <structfield>magic</structfield> field</title> 529 <tgroup cols="3"> 530 &cs-def; 531 <thead> 532 <row> 533 <entry align="left">Defined Symbol</entry> 534 <entry align="left">Value</entry> 535 <entry align="left">Description</entry> 536 </row> 537 </thead> 538 <tbody valign="top"> 539 <row> 540 <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC0</constant> 541 </entry> 542 <entry>"itv0"</entry> 543 <entry>Indicates the <structfield>itv0</structfield> 544 member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid.</entry> 545 </row> 546 <row> 547 <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC1</constant> 548 </entry> 549 <entry>"ITV0"</entry> 550 <entry>Indicates the <structfield>ITV0</structfield> 551 member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid and 552 that 36 lines of sliced VBI data are present.</entry> 553 </row> 554 </tbody> 555 </tgroup> 556 </table> 557 558 <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0"> 559 <title>struct <structname>v4l2_mpeg_vbi_itv0</structname> 560 </title> 561 <tgroup cols="3"> 562 &cs-str; 563 <tbody valign="top"> 564 <row> 565 <entry>__le32</entry> 566 <entry><structfield>linemask</structfield>[2]</entry> 567 <entry><para>Bitmasks indicating the VBI service lines 568 present. These <structfield>linemask</structfield> values are stored 569 in little endian byte order in the MPEG stream. Some reference 570 <structfield>linemask</structfield> bit positions with their 571 corresponding VBI line number and video field are given below. 572 b<subscript>0</subscript> indicates the least significant bit of a 573 <structfield>linemask</structfield> value:<screen> 574 <structfield>linemask</structfield>[0] b<subscript>0</subscript>: line 6 first field 575 <structfield>linemask</structfield>[0] b<subscript>17</subscript>: line 23 first field 576 <structfield>linemask</structfield>[0] b<subscript>18</subscript>: line 6 second field 577 <structfield>linemask</structfield>[0] b<subscript>31</subscript>: line 19 second field 578 <structfield>linemask</structfield>[1] b<subscript>0</subscript>: line 20 second field 579 <structfield>linemask</structfield>[1] b<subscript>3</subscript>: line 23 second field 580 <structfield>linemask</structfield>[1] b<subscript>4</subscript>-b<subscript>31</subscript>: unused and set to 0</screen></para></entry> 581 </row> 582 <row> 583 <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line"> 584 <structname>v4l2_mpeg_vbi_itv0_line</structname></link> 585 </entry> 586 <entry><structfield>line</structfield>[35]</entry> 587 <entry>This is a variable length array that holds from 1 588 to 35 lines of sliced VBI data. The sliced VBI data lines present 589 correspond to the bits set in the <structfield>linemask</structfield> 590 array, starting from b<subscript>0</subscript> of <structfield> 591 linemask</structfield>[0] up through b<subscript>31</subscript> of 592 <structfield>linemask</structfield>[0], and from b<subscript>0 593 </subscript> of <structfield>linemask</structfield>[1] up through b 594 <subscript>3</subscript> of <structfield>linemask</structfield>[1]. 595 <structfield>line</structfield>[0] corresponds to the first bit 596 found set in the <structfield>linemask</structfield> array, 597 <structfield>line</structfield>[1] corresponds to the second bit 598 found set in the <structfield>linemask</structfield> array, etc. 599 If no <structfield>linemask</structfield> array bits are set, then 600 <structfield>line</structfield>[0] may contain one line of 601 unspecified data that should be ignored by applications.</entry> 602 </row> 603 </tbody> 604 </tgroup> 605 </table> 606 607 <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-1"> 608 <title>struct <structname>v4l2_mpeg_vbi_ITV0</structname> 609 </title> 610 <tgroup cols="3"> 611 &cs-str; 612 <tbody valign="top"> 613 <row> 614 <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line"> 615 <structname>v4l2_mpeg_vbi_itv0_line</structname></link> 616 </entry> 617 <entry><structfield>line</structfield>[36]</entry> 618 <entry>A fixed length array of 36 lines of sliced VBI 619 data. <structfield>line</structfield>[0] through <structfield>line 620 </structfield>[17] correspond to lines 6 through 23 of the 621 first field. <structfield>line</structfield>[18] through 622 <structfield>line</structfield>[35] corresponds to lines 6 623 through 23 of the second field.</entry> 624 </row> 625 </tbody> 626 </tgroup> 627 </table> 628 629 <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-line"> 630 <title>struct <structname>v4l2_mpeg_vbi_itv0_line</structname> 631 </title> 632 <tgroup cols="3"> 633 &cs-str; 634 <tbody valign="top"> 635 <row> 636 <entry>__u8</entry> 637 <entry><structfield>id</structfield></entry> 638 <entry>A line identifier value from 639 <xref linkend="ITV0-Line-Identifier-Constants" /> that indicates 640 the type of sliced VBI data stored on this line.</entry> 641 </row> 642 <row> 643 <entry>__u8</entry> 644 <entry><structfield>data</structfield>[42]</entry> 645 <entry>The sliced VBI data for the line.</entry> 646 </row> 647 </tbody> 648 </tgroup> 649 </table> 650 651 <table frame="none" pgwide="1" id="ITV0-Line-Identifier-Constants"> 652 <title>Line Identifiers for struct <link 653 linkend="v4l2-mpeg-vbi-itv0-line"><structname> 654 v4l2_mpeg_vbi_itv0_line</structname></link> <structfield>id 655 </structfield> field</title> 656 <tgroup cols="3"> 657 &cs-def; 658 <thead> 659 <row> 660 <entry align="left">Defined Symbol</entry> 661 <entry align="left">Value</entry> 662 <entry align="left">Description</entry> 663 </row> 664 </thead> 665 <tbody valign="top"> 666 <row> 667 <entry><constant>V4L2_MPEG_VBI_IVTV_TELETEXT_B</constant> 668 </entry> 669 <entry>1</entry> 670 <entry>Refer to <link linkend="vbi-services2"> 671 Sliced VBI services</link> for a description of the line payload.</entry> 672 </row> 673 <row> 674 <entry><constant>V4L2_MPEG_VBI_IVTV_CAPTION_525</constant> 675 </entry> 676 <entry>4</entry> 677 <entry>Refer to <link linkend="vbi-services2"> 678 Sliced VBI services</link> for a description of the line payload.</entry> 679 </row> 680 <row> 681 <entry><constant>V4L2_MPEG_VBI_IVTV_WSS_625</constant> 682 </entry> 683 <entry>5</entry> 684 <entry>Refer to <link linkend="vbi-services2"> 685 Sliced VBI services</link> for a description of the line payload.</entry> 686 </row> 687 <row> 688 <entry><constant>V4L2_MPEG_VBI_IVTV_VPS</constant> 689 </entry> 690 <entry>7</entry> 691 <entry>Refer to <link linkend="vbi-services2"> 692 Sliced VBI services</link> for a description of the line payload.</entry> 693 </row> 694 </tbody> 695 </tgroup> 696 </table> 697 698 </section> 699 </section> 700 701 702 <!-- 703 Local Variables: 704 mode: sgml 705 sgml-parent-document: "v4l2.sgml" 706 indent-tabs-mode: nil 707 End: 708 -->
