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1 <title>Sliced VBI Data Interface</title>
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>
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>
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>
26 <section>
27 <title>Querying Capabilities</title>
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>
39 <section>
40 <title>Supplemental Functions</title>
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>
51 <section id="sliced-vbi-format-negotitation">
52 <title>Sliced VBI Format Negotiation</title>
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>
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>
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>
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>
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>
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>
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>
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>
292 <section>
293 <title>Reading and writing sliced VBI data</title>
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>
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>
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>
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>
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>
387 </section>
389 <section>
390 <title>Sliced VBI Data in MPEG Streams</title>
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>
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>
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>
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>
421 <para>The following subsections specify the format of the
422 embedded sliced VBI data.</para>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
698 </section>
699 </section>
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