1 <title>Sliced VBI Data Interface</title> 2 3 <para>VBI stands for Vertical Blanking Interval, a gap in the 4sequence of lines of an analog video signal. During VBI no picture 5information is transmitted, allowing some time while the electron beam 6of 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 9in the VBI. V4L2 drivers shall <emphasis>not</emphasis> do this by 10software, see also the <link linkend="raw-vbi">raw VBI 11interface</link>. The data is passed as short packets of fixed size, 12covering one scan line each. The number of packets per video frame is 13variable.</para> 14 15 <para>Sliced VBI capture and output devices are accessed through the 16same character special files as raw VBI devices. When a driver 17supports both interfaces, the default function of a 18<filename>/dev/vbi</filename> device is <emphasis>raw</emphasis> VBI 19capturing or output, and the sliced VBI function is only available 20after calling the &VIDIOC-S-FMT; ioctl as defined below. Likewise a 21<filename>/dev/video</filename> device may support the sliced VBI API, 22however the default function here is video capturing or output. 23Different file descriptors must be used to pass raw and sliced VBI 24data 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 30set the <constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant> or 31<constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant> flag respectively, in 32the <structfield>capabilities</structfield> field of &v4l2-capability; 33returned by the &VIDIOC-QUERYCAP; ioctl. At least one of the 34read/write, streaming or asynchronous <link linkend="io">I/O 35methods</link> must be supported. Sliced VBI devices may have a tuner 36or modulator.</para> 37 </section> 38 39 <section> 40 <title>Supplemental Functions</title> 41 42 <para>Sliced VBI devices shall support <link linkend="video">video 43input or output</link> and <link linkend="tuner">tuner or 44modulator</link> ioctls if they have these capabilities, and they may 45support <link linkend="control">control</link> ioctls. The <link 46linkend="standard">video standard</link> ioctls provide information 47vital to program a sliced VBI device, therefore must be 48supported.</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 55hardware applications can call the &VIDIOC-G-SLICED-VBI-CAP; ioctl. 56All drivers implementing the sliced VBI interface must support this 57ioctl. The results may differ from those of the &VIDIOC-S-FMT; ioctl 58when the number of VBI lines the hardware can capture or output per 59frame, or the number of services it can identify on a given line are 60limited. For example on PAL line 16 the hardware may be able to look 61for a VPS or Teletext signal, but not both at the same time.</para> 62 63 <para>To determine the currently selected services applications 64set the <structfield>type </structfield> field of &v4l2-format; to 65<constant> V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> or <constant> 66V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant>, and the &VIDIOC-G-FMT; 67ioctl fills the <structfield>fmt.sliced</structfield> member, a 68&v4l2-sliced-vbi-format;.</para> 69 70 <para>Applications can request different parameters by 71initializing or modifying the <structfield>fmt.sliced</structfield> 72member 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 76because the hardware must be told which VBI service to expect on each 77scan line. Not all services may be supported by the hardware on all 78lines (this is especially true for VBI output where Teletext is often 79unsupported and other services can only be inserted in one specific 80line). In many cases, however, it is sufficient to just set the 81<structfield>service_set</structfield> field to the required services 82and let the driver fill the <structfield>service_lines</structfield> 83array according to hardware capabilities. Only if more precise control 84is 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 88according to hardware capabilities. When the driver allocates 89resources at this point, it may return an &EBUSY; if the required 90resources are temporarily unavailable. Other resource allocation 91points 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 113driver according to the services specified in this field. For example, 114if <structfield>service_set</structfield> is initialized with 115<constant>V4L2_SLICED_TELETEXT_B | V4L2_SLICED_WSS_625</constant>, a 116driver for the cx25840 video decoder sets lines 7-22 of both 117fields<footnote><para>According to <link 118linkend="ets300706">ETS 300 706</link> lines 6-22 of the 119first field and lines 5-22 of the second field may carry Teletext 120data.</para></footnote> to <constant>V4L2_SLICED_TELETEXT_B</constant> 121and 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 124of <structfield>service_lines</structfield> will be used instead. 125</para><para>On return the driver sets this field to the union of all 126elements of the returned <structfield>service_lines</structfield> 127array. It may contain less services than requested, perhaps just one, 128if the hardware cannot handle more services simultaneously. It may be 129empty (zero) if none of the requested services are supported by the 130hardware.</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 136array with sets of data services the driver shall look for or insert 137on the respective scan line. Subject to hardware capabilities drivers 138return the requested set, a subset, which may be just a single 139service, or an empty set. When the hardware cannot handle multiple 140services on the same line the driver shall choose one. No assumptions 141can be made on which service the driver chooses.</para><para>Data 142services are defined in <xref linkend="vbi-services2" />. Array indices 143map to ITU-R line numbers (see also <xref linkend="vbi-525" /> and <xref 144 linkend="vbi-625" />) as follows: <!-- No nested 145tables, 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 194one &func-read; or &func-write; call, and the buffer size in bytes for 195the &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. Drivers set this field to 196the size of &v4l2-sliced-vbi-data; times the number of non-zero 197elements in the returned <structfield>service_lines</structfield> 198array (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 204extensions. 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 237without 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 245ETS 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 253bit, 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> 261Byte 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 270line 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 276line systems.</entry> 277 </row> 278 </tbody> 279 </tgroup> 280 </table> 281 282 <para>Drivers may return an &EINVAL; when applications attempt to 283read or write data without prior format negotiation, after switching 284the video standard (which may invalidate the negotiated VBI 285parameters) and after switching the video input (which may change the 286video standard as a side effect). The &VIDIOC-S-FMT; ioctl may return 287an &EBUSY; when applications attempt to change the format while i/o is 288in progress (between a &VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; call, 289and 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 296belonging to one video frame. That is an array of 297<structname>v4l2_sliced_vbi_data</structname> structures with one or 298more elements and a total size not exceeding 299<structfield>io_size</structfield> bytes. Likewise in streaming I/O 300mode one buffer of <structfield>io_size</structfield> bytes must 301contain data of one video frame. The <structfield>id</structfield> of 302unused <structname>v4l2_sliced_vbi_data</structname> elements must be 303zero.</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" /> 315identifying the type of data in this packet. Only a single bit must be 316set. When the <structfield>id</structfield> of a captured packet is 317zero, the packet is empty and the contents of other fields are 318undefined. Applications shall ignore empty packets. When the 319<structfield>id</structfield> of a packet for output is zero the 320contents of the <structfield>data</structfield> field are undefined 321and 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 329from, or shall be inserted at. <constant>0</constant> for the first 330field, <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 336data has been captured from, or shall be inserted at. See <xref 337 linkend="vbi-525" /> and <xref linkend="vbi-625" /> for valid 338values. Sliced VBI capture devices can set the line number of all 339packets to <constant>0</constant> if the hardware cannot reliably 340identify 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. 346Applications 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 353bytes passed for each data type. The contents of padding bytes at the 354end of this array are undefined, drivers and applications shall ignore 355them.</entry> 356 </row> 357 </tbody> 358 </tgroup> 359 </table> 360 361 <para>Packets are always passed in ascending line number order, 362without duplicate line numbers. The &func-write; function and the 363&VIDIOC-QBUF; ioctl must return an &EINVAL; when applications violate 364this rule. They must also return an &EINVAL; when applications pass an 365incorrect 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 369unknown the driver must pass the packets in transmitted order. The 370driver can insert empty packets with <structfield>id</structfield> set 371to zero anywhere in the packet array.</para> 372 373 <para>To assure synchronization and to distinguish from frame 374dropping, when a captured frame does not carry any of the requested 375data services drivers must pass one or more empty packets. When an 376application fails to pass VBI data in time for output, the driver 377must output the last VPS and WSS packet again, and disable the output 378of Closed Caption and Teletext data, or output data which is ignored 379by Closed Caption and Teletext decoders.</para> 380 381 <para>A sliced VBI device may support <link 382linkend="rw">read/write</link> and/or streaming (<link 383linkend="mmap">memory mapping</link> and/or <link linkend="userp">user 384pointer</link>) I/O. The latter bears the possibility of synchronizing 385video 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 393capable of providing <link 394linkend="sliced-vbi-format-negotitation">negotiated sliced VBI 395services</link> as data embedded in the MPEG stream. Users or 396applications control this sliced VBI data insertion with the <link 397linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> 398control.</para> 399 400 <para>If the driver does not provide the <link 401linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> 402control, or only allows that control to be set to <link 403linkend="v4l2-mpeg-stream-vbi-fmt"><constant> 404V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link>, then the device 405cannot embed sliced VBI data in the MPEG stream.</para> 406 407 <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"> 408V4L2_CID_MPEG_STREAM_VBI_FMT</link> control does not implicitly set 409the device driver to capture nor cease capturing sliced VBI data. The 410control only indicates to embed sliced VBI data in the MPEG stream, if 411an 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 414data in only certain types of MPEG streams: for example in an MPEG-2 415PS but not an MPEG-2 TS. In this situation, if sliced VBI data 416insertion is requested, the sliced VBI data will be embedded in MPEG 417stream types when supported, and silently omitted from MPEG stream 418types where sliced VBI data insertion is not supported by the device. 419</para> 420 421 <para>The following subsections specify the format of the 422embedded 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> 427V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link> embedded sliced VBI 428format shall be interpreted by drivers as a control to cease 429embedding sliced VBI data in MPEG streams. Neither the device nor 430driver shall insert "empty" embedded sliced VBI data packets in the 431MPEG stream when this format is set. No MPEG stream data structures 432are 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> 438V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> embedded sliced VBI 439format, when supported, indicates to the driver to embed up to 36 440lines of sliced VBI data per frame in an MPEG-2 <emphasis>Private 441Stream 1 PES</emphasis> packet encapsulated in an MPEG-2 <emphasis> 442Program Pack</emphasis> in the MPEG stream.</para> 443 444 <para><emphasis>Historical context</emphasis>: This format 445specification originates from a custom, embedded, sliced VBI data 446format used by the <filename>ivtv</filename> driver. This format 447has already been informally specified in the kernel sources in the 448file <filename>Documentation/video4linux/cx2341x/README.vbi</filename> 449. The maximum size of the payload and other aspects of this format 450are driven by the CX23415 MPEG decoder's capabilities and limitations 451with respect to extracting, decoding, and displaying sliced VBI data 452embedded within an MPEG stream.</para> 453 454 <para>This format's use is <emphasis>not</emphasis> exclusive to 455the <filename>ivtv</filename> driver <emphasis>nor</emphasis> 456exclusive to CX2341x devices, as the sliced VBI data packet insertion 457into the MPEG stream is implemented in driver software. At least the 458<filename>cx18</filename> driver provides sliced VBI data insertion 459into an MPEG-2 PS in this format as well.</para> 460 461 <para>The following definitions specify the payload of the 462MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packets that contain 463sliced 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 466and encapsulating MPEG-2 <emphasis>Program Pack</emphasis> header are 467not detailed here. Please refer to the MPEG-2 specifications for 468details 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 473length, depending on the actual number of lines of sliced VBI data 474present in a video frame. The payload may be padded at the end with 475unspecified fill bytes to align the end of the payload to a 4-byte 476boundary. The payload shall never exceed 1552 bytes (2 fields with 47718 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 492this is a valid sliced VBI data payload and also indicates which 493member 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 507that contains anywhere from 1 to 35 lines of sliced VBI data. 508Line masks are provided in this form of the payload indicating 509which 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 518used when 36 lines of sliced VBI data are present. No line masks are 519provided in this form of the payload; all valid line mask bits are 520implcitly 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> 544member 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> 551member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid and 552that 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 568present. These <structfield>linemask</structfield> values are stored 569in little endian byte order in the MPEG stream. Some reference 570<structfield>linemask</structfield> bit positions with their 571corresponding VBI line number and video field are given below. 572b<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 588to 35 lines of sliced VBI data. The sliced VBI data lines present 589correspond to the bits set in the <structfield>linemask</structfield> 590array, starting from b<subscript>0</subscript> of <structfield> 591linemask</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 596found set in the <structfield>linemask</structfield> array, 597<structfield>line</structfield>[1] corresponds to the second bit 598found set in the <structfield>linemask</structfield> array, etc. 599If no <structfield>linemask</structfield> array bits are set, then 600<structfield>line</structfield>[0] may contain one line of 601unspecified 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 619data. <structfield>line</structfield>[0] through <structfield>line 620</structfield>[17] correspond to lines 6 through 23 of the 621first field. <structfield>line</structfield>[18] through 622<structfield>line</structfield>[35] corresponds to lines 6 623through 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 640the 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> 654v4l2_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"> 671Sliced 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"> 678Sliced 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"> 685Sliced 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"> 692Sliced 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