1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _sliced:
5
6 *************************
7 Sliced VBI Data Interface
8 *************************
9
10 VBI stands for Vertical Blanking Interval, a gap in the sequence of
11 lines of an analog video signal. During VBI no picture information is
12 transmitted, allowing some time while the electron beam of a cathode ray
13 tube TV returns to the top of the screen.
14
15 Sliced VBI devices use hardware to demodulate data transmitted in the
16 VBI. V4L2 drivers shall *not* do this by software, see also the
17 :ref:`raw VBI interface <raw-vbi>`. The data is passed as short
18 packets of fixed size, covering one scan line each. The number of
19 packets per video frame is variable.
20
21 Sliced VBI capture and output devices are accessed through the same
22 character special files as raw VBI devices. When a driver supports both
23 interfaces, the default function of a ``/dev/vbi`` device is *raw* VBI
24 capturing or output, and the sliced VBI function is only available after
25 calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl as defined
26 below. Likewise a ``/dev/video`` device may support the sliced VBI API,
27 however the default function here is video capturing or output.
28 Different file descriptors must be used to pass raw and sliced VBI data
29 simultaneously, if this is supported by the driver.
30
31 Querying Capabilities
32 =====================
33
34 Devices supporting the sliced VBI capturing or output API set the
35 ``V4L2_CAP_SLICED_VBI_CAPTURE`` or ``V4L2_CAP_SLICED_VBI_OUTPUT`` flag
36 respectively, in the ``capabilities`` field of struct
37 :c:type:`v4l2_capability` returned by the
38 :ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
39 read/write or streaming :ref:`I/O methods <io>` must be
40 supported. Sliced VBI devices may have a tuner or modulator.
41
42 Supplemental Functions
43 ======================
44
45 Sliced VBI devices shall support :ref:`video input or output <video>`
46 and :ref:`tuner or modulator <tuner>` ioctls if they have these
47 capabilities, and they may support :ref:`control` ioctls.
48 The :ref:`video standard <standard>` ioctls provide information vital
49 to program a sliced VBI device, therefore must be supported.
50
51 .. _sliced-vbi-format-negotitation:
52
53 Sliced VBI Format Negotiation
54 =============================
55
56 To find out which data services are supported by the hardware
57 applications can call the
58 :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl.
59 All drivers implementing the sliced VBI interface must support this
60 ioctl. The results may differ from those of the
61 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl when the number of VBI
62 lines the hardware can capture or output per frame, or the number of
63 services it can identify on a given line are limited. For example on PAL
64 line 16 the hardware may be able to look for a VPS or Teletext signal,
65 but not both at the same time.
66
67 To determine the currently selected services applications set the
68 ``type`` field of struct :c:type:`v4l2_format` to
69 ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` or
70 ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``, and the
71 :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl fills the ``fmt.sliced``
72 member, a struct
73 :c:type:`v4l2_sliced_vbi_format`.
74
75 Applications can request different parameters by initializing or
76 modifying the ``fmt.sliced`` member and calling the
77 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with a pointer to the
78 struct :c:type:`v4l2_format` structure.
79
80 The sliced VBI API is more complicated than the raw VBI API because the
81 hardware must be told which VBI service to expect on each scan line. Not
82 all services may be supported by the hardware on all lines (this is
83 especially true for VBI output where Teletext is often unsupported and
84 other services can only be inserted in one specific line). In many
85 cases, however, it is sufficient to just set the ``service_set`` field
86 to the required services and let the driver fill the ``service_lines``
87 array according to hardware capabilities. Only if more precise control
88 is needed should the programmer set the ``service_lines`` array
89 explicitly.
90
91 The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl modifies the parameters
92 according to hardware capabilities. When the driver allocates resources
93 at this point, it may return an ``EBUSY`` error code if the required
94 resources are temporarily unavailable. Other resource allocation points
95 which may return ``EBUSY`` can be the
96 :ref:`VIDIOC_STREAMON` ioctl and the first
97 :c:func:`read()`, :c:func:`write()` and
98 :c:func:`select()` call.
99
100 .. c:type:: v4l2_sliced_vbi_format
101
102 struct v4l2_sliced_vbi_format
103 -----------------------------
104
105 .. raw:: latex
106
107 \begingroup
108 \scriptsize
109 \setlength{\tabcolsep}{2pt}
110
111 .. tabularcolumns:: |p{.85cm}|p{3.3cm}|p{4.45cm}|p{4.45cm}|p{4.45cm}|
112
113 .. cssclass:: longtable
114
115 .. flat-table::
116 :header-rows: 0
117 :stub-columns: 0
118 :widths: 3 3 2 2 2
119
120 * - __u16
121 - ``service_set``
122 - :cspan:`2`
123
124 If ``service_set`` is non-zero when passed with
125 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` or
126 :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>`, the ``service_lines``
127 array will be filled by the driver according to the services
128 specified in this field. For example, if ``service_set`` is
129 initialized with ``V4L2_SLICED_TELETEXT_B | V4L2_SLICED_WSS_625``,
130 a driver for the cx25840 video decoder sets lines 7-22 of both
131 fields [#f1]_ to ``V4L2_SLICED_TELETEXT_B`` and line 23 of the first
132 field to ``V4L2_SLICED_WSS_625``. If ``service_set`` is set to
133 zero, then the values of ``service_lines`` will be used instead.
134
135 On return the driver sets this field to the union of all elements
136 of the returned ``service_lines`` array. It may contain less
137 services than requested, perhaps just one, if the hardware cannot
138 handle more services simultaneously. It may be empty (zero) if
139 none of the requested services are supported by the hardware.
140 * - __u16
141 - ``service_lines``\ [2][24]
142 - :cspan:`2`
143
144 Applications initialize this array with sets of data services the
145 driver shall look for or insert on the respective scan line.
146 Subject to hardware capabilities drivers return the requested set,
147 a subset, which may be just a single service, or an empty set.
148 When the hardware cannot handle multiple services on the same line
149 the driver shall choose one. No assumptions can be made on which
150 service the driver chooses.
151
152 Data services are defined in :ref:`vbi-services2`. Array indices
153 map to ITU-R line numbers\ [#f2]_ as follows:
154 * -
155 -
156 - Element
157 - 525 line systems
158 - 625 line systems
159 * -
160 -
161 - ``service_lines``\ [0][1]
162 - 1
163 - 1
164 * -
165 -
166 - ``service_lines``\ [0][23]
167 - 23
168 - 23
169 * -
170 -
171 - ``service_lines``\ [1][1]
172 - 264
173 - 314
174 * -
175 -
176 - ``service_lines``\ [1][23]
177 - 286
178 - 336
179 * -
180 -
181 - :cspan:`2` Drivers must set ``service_lines`` [0][0] and
182 ``service_lines``\ [1][0] to zero. The
183 ``V4L2_VBI_ITU_525_F1_START``, ``V4L2_VBI_ITU_525_F2_START``,
184 ``V4L2_VBI_ITU_625_F1_START`` and ``V4L2_VBI_ITU_625_F2_START``
185 defines give the start line numbers for each field for each 525 or
186 625 line format as a convenience. Don't forget that ITU line
187 numbering starts at 1, not 0.
188 * - __u32
189 - ``io_size``
190 - :cspan:`2` Maximum number of bytes passed by one
191 :c:func:`read()` or :c:func:`write()` call,
192 and the buffer size in bytes for the
193 :ref:`VIDIOC_QBUF` and
194 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. Drivers set this field
195 to the size of struct
196 :c:type:`v4l2_sliced_vbi_data` times the
197 number of non-zero elements in the returned ``service_lines``
198 array (that is the number of lines potentially carrying data).
199 * - __u32
200 - ``reserved``\ [2]
201 - :cspan:`2` This array is reserved for future extensions.
202
203 Applications and drivers must set it to zero.
204
205 .. raw:: latex
206
207 \endgroup
208
209 .. _vbi-services2:
210
211 Sliced VBI services
212 -------------------
213
214 .. raw:: latex
215
216 \footnotesize
217
218 .. tabularcolumns:: |p{4.2cm}|p{1.1cm}|p{2.1cm}|p{2.0cm}|p{6.5cm}|
219
220 .. flat-table::
221 :header-rows: 1
222 :stub-columns: 0
223 :widths: 2 1 1 2 2
224
225 * - Symbol
226 - Value
227 - Reference
228 - Lines, usually
229 - Payload
230 * - ``V4L2_SLICED_TELETEXT_B`` (Teletext System B)
231 - 0x0001
232 - :ref:`ets300706`,
233
234 :ref:`itu653`
235 - PAL/SECAM line 7-22, 320-335 (second field 7-22)
236 - Last 42 of the 45 byte Teletext packet, that is without clock
237 run-in and framing code, lsb first transmitted.
238 * - ``V4L2_SLICED_VPS``
239 - 0x0400
240 - :ref:`ets300231`
241 - PAL line 16
242 - Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb
243 first transmitted.
244 * - ``V4L2_SLICED_CAPTION_525``
245 - 0x1000
246 - :ref:`cea608`
247 - NTSC line 21, 284 (second field 21)
248 - Two bytes in transmission order, including parity bit, lsb first
249 transmitted.
250 * - ``V4L2_SLICED_WSS_625``
251 - 0x4000
252 - :ref:`itu1119`,
253
254 :ref:`en300294`
255 - PAL/SECAM line 23
256 - See :ref:`v4l2-sliced-wss-625-payload` below.
257 * - ``V4L2_SLICED_VBI_525``
258 - 0x1000
259 - :cspan:`2` Set of services applicable to 525 line systems.
260 * - ``V4L2_SLICED_VBI_625``
261 - 0x4401
262 - :cspan:`2` Set of services applicable to 625 line systems.
263
264 .. raw:: latex
265
266 \normalsize
267
268 Drivers may return an ``EINVAL`` error code when applications attempt to
269 read or write data without prior format negotiation, after switching the
270 video standard (which may invalidate the negotiated VBI parameters) and
271 after switching the video input (which may change the video standard as
272 a side effect). The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl may
273 return an ``EBUSY`` error code when applications attempt to change the
274 format while i/o is in progress (between a
275 :ref:`VIDIOC_STREAMON` and
276 :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` call, and after the first
277 :c:func:`read()` or :c:func:`write()` call).
278
279 .. _v4l2-sliced-wss-625-payload:
280
281 V4L2_SLICED_WSS_625 payload
282 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
283
284 The payload for ``V4L2_SLICED_WSS_625`` is:
285
286 +-----+------------------+-----------------------+
287 |Byte | 0 | 1 |
288 +-----+--------+---------+-----------+-----------+
289 | | msb | lsb | msb | lsb |
290 | +-+-+-+--+--+-+-+--+--+-+--+---+---+--+-+--+
291 | Bit |7|6|5|4 | 3|2|1|0 | x|x|13|12 | 11|10|9|8 |
292 +-----+-+-+-+--+--+-+-+--+--+-+--+---+---+--+-+--+
293
294 Reading and writing sliced VBI data
295 ===================================
296
297 A single :c:func:`read()` or :c:func:`write()`
298 call must pass all data belonging to one video frame. That is an array
299 of struct :c:type:`v4l2_sliced_vbi_data` structures with one or
300 more elements and a total size not exceeding ``io_size`` bytes. Likewise
301 in streaming I/O mode one buffer of ``io_size`` bytes must contain data
302 of one video frame. The ``id`` of unused
303 struct :c:type:`v4l2_sliced_vbi_data` elements must be zero.
304
305 .. c:type:: v4l2_sliced_vbi_data
306
307 struct v4l2_sliced_vbi_data
308 ---------------------------
309
310 .. tabularcolumns:: |p{1.2cm}|p{2.2cm}|p{13.9cm}|
311
312 .. flat-table::
313 :header-rows: 0
314 :stub-columns: 0
315 :widths: 3 1 4
316
317 * - __u32
318 - ``id``
319 - A flag from :ref:`vbi-services` identifying the type of data in
320 this packet. Only a single bit must be set. When the ``id`` of a
321 captured packet is zero, the packet is empty and the contents of
322 other fields are undefined. Applications shall ignore empty
323 packets. When the ``id`` of a packet for output is zero the
324 contents of the ``data`` field are undefined and the driver must
325 no longer insert data on the requested ``field`` and ``line``.
326 * - __u32
327 - ``field``
328 - The video field number this data has been captured from, or shall
329 be inserted at. ``0`` for the first field, ``1`` for the second
330 field.
331 * - __u32
332 - ``line``
333 - The field (as opposed to frame) line number this data has been
334 captured from, or shall be inserted at. See :ref:`vbi-525` and
335 :ref:`vbi-625` for valid values. Sliced VBI capture devices can
336 set the line number of all packets to ``0`` if the hardware cannot
337 reliably identify scan lines. The field number must always be
338 valid.
339 * - __u32
340 - ``reserved``
341 - This field is reserved for future extensions. Applications and
342 drivers must set it to zero.
343 * - __u8
344 - ``data``\ [48]
345 - The packet payload. See :ref:`vbi-services` for the contents and
346 number of bytes passed for each data type. The contents of padding
347 bytes at the end of this array are undefined, drivers and
348 applications shall ignore them.
349
350 Packets are always passed in ascending line number order, without
351 duplicate line numbers. The :c:func:`write()` function and
352 the :ref:`VIDIOC_QBUF` ioctl must return an ``EINVAL``
353 error code when applications violate this rule. They must also return an
354 EINVAL error code when applications pass an incorrect field or line
355 number, or a combination of ``field``, ``line`` and ``id`` which has not
356 been negotiated with the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` or
357 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. When the line numbers are
358 unknown the driver must pass the packets in transmitted order. The
359 driver can insert empty packets with ``id`` set to zero anywhere in the
360 packet array.
361
362 To assure synchronization and to distinguish from frame dropping, when a
363 captured frame does not carry any of the requested data services drivers
364 must pass one or more empty packets. When an application fails to pass
365 VBI data in time for output, the driver must output the last VPS and WSS
366 packet again, and disable the output of Closed Caption and Teletext
367 data, or output data which is ignored by Closed Caption and Teletext
368 decoders.
369
370 A sliced VBI device may support :ref:`read/write <rw>` and/or
371 streaming (:ref:`memory mapping <mmap>` and/or
372 :ref:`user pointer <userp>`) I/O. The latter bears the possibility of
373 synchronizing video and VBI data by using buffer timestamps.
374
375 Sliced VBI Data in MPEG Streams
376 ===============================
377
378 If a device can produce an MPEG output stream, it may be capable of
379 providing
380 :ref:`negotiated sliced VBI services <sliced-vbi-format-negotitation>`
381 as data embedded in the MPEG stream. Users or applications control this
382 sliced VBI data insertion with the
383 :ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
384 control.
385
386 If the driver does not provide the
387 :ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
388 control, or only allows that control to be set to
389 :ref:`V4L2_MPEG_STREAM_VBI_FMT_NONE <v4l2-mpeg-stream-vbi-fmt>`,
390 then the device cannot embed sliced VBI data in the MPEG stream.
391
392 The
393 :ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
394 control does not implicitly set the device driver to capture nor cease
395 capturing sliced VBI data. The control only indicates to embed sliced
396 VBI data in the MPEG stream, if an application has negotiated sliced VBI
397 service be captured.
398
399 It may also be the case that a device can embed sliced VBI data in only
400 certain types of MPEG streams: for example in an MPEG-2 PS but not an
401 MPEG-2 TS. In this situation, if sliced VBI data insertion is requested,
402 the sliced VBI data will be embedded in MPEG stream types when
403 supported, and silently omitted from MPEG stream types where sliced VBI
404 data insertion is not supported by the device.
405
406 The following subsections specify the format of the embedded sliced VBI
407 data.
408
409 MPEG Stream Embedded, Sliced VBI Data Format: NONE
410 --------------------------------------------------
411
412 The
413 :ref:`V4L2_MPEG_STREAM_VBI_FMT_NONE <v4l2-mpeg-stream-vbi-fmt>`
414 embedded sliced VBI format shall be interpreted by drivers as a control
415 to cease embedding sliced VBI data in MPEG streams. Neither the device
416 nor driver shall insert "empty" embedded sliced VBI data packets in the
417 MPEG stream when this format is set. No MPEG stream data structures are
418 specified for this format.
419
420 MPEG Stream Embedded, Sliced VBI Data Format: IVTV
421 --------------------------------------------------
422
423 The
424 :ref:`V4L2_MPEG_STREAM_VBI_FMT_IVTV <v4l2-mpeg-stream-vbi-fmt>`
425 embedded sliced VBI format, when supported, indicates to the driver to
426 embed up to 36 lines of sliced VBI data per frame in an MPEG-2 *Private
427 Stream 1 PES* packet encapsulated in an MPEG-2 *Program Pack* in the
428 MPEG stream.
429
430 *Historical context*: This format specification originates from a
431 custom, embedded, sliced VBI data format used by the ``ivtv`` driver.
432 This format has already been informally specified in the kernel sources
433 in the file ``Documentation/userspace-api/media/drivers/cx2341x-uapi.rst`` . The
434 maximum size of the payload and other aspects of this format are driven
435 by the CX23415 MPEG decoder's capabilities and limitations with respect
436 to extracting, decoding, and displaying sliced VBI data embedded within
437 an MPEG stream.
438
439 This format's use is *not* exclusive to the ``ivtv`` driver *nor*
440 exclusive to CX2341x devices, as the sliced VBI data packet insertion
441 into the MPEG stream is implemented in driver software. At least the
442 ``cx18`` driver provides sliced VBI data insertion into an MPEG-2 PS in
443 this format as well.
444
445 The following definitions specify the payload of the MPEG-2 *Private
446 Stream 1 PES* packets that contain sliced VBI data when
447 :ref:`V4L2_MPEG_STREAM_VBI_FMT_IVTV <v4l2-mpeg-stream-vbi-fmt>`
448 is set. (The MPEG-2 *Private Stream 1 PES* packet header and
449 encapsulating MPEG-2 *Program Pack* header are not detailed here. Please
450 refer to the MPEG-2 specifications for details on those packet headers.)
451
452 The payload of the MPEG-2 *Private Stream 1 PES* packets that contain
453 sliced VBI data is specified by struct
454 :c:type:`v4l2_mpeg_vbi_fmt_ivtv`. The
455 payload is variable length, depending on the actual number of lines of
456 sliced VBI data present in a video frame. The payload may be padded at
457 the end with unspecified fill bytes to align the end of the payload to a
458 4-byte boundary. The payload shall never exceed 1552 bytes (2 fields
459 with 18 lines/field with 43 bytes of data/line and a 4 byte magic
460 number).
461
462 .. c:type:: v4l2_mpeg_vbi_fmt_ivtv
463
464 struct v4l2_mpeg_vbi_fmt_ivtv
465 -----------------------------
466
467 .. tabularcolumns:: |p{4.2cm}|p{2.0cm}|p{11.1cm}|
468
469 .. flat-table::
470 :header-rows: 0
471 :stub-columns: 0
472 :widths: 1 1 2
473
474 * - __u8
475 - ``magic``\ [4]
476 - A "magic" constant from :ref:`v4l2-mpeg-vbi-fmt-ivtv-magic` that
477 indicates this is a valid sliced VBI data payload and also
478 indicates which member of the anonymous union, ``itv0`` or
479 ``ITV0``, to use for the payload data.
480 * - union {
481 - (anonymous)
482 * - struct :c:type:`v4l2_mpeg_vbi_itv0`
483 - ``itv0``
484 - The primary form of the sliced VBI data payload that contains
485 anywhere from 1 to 35 lines of sliced VBI data. Line masks are
486 provided in this form of the payload indicating which VBI lines
487 are provided.
488 * - struct :ref:`v4l2_mpeg_vbi_ITV0 <v4l2-mpeg-vbi-itv0-1>`
489 - ``ITV0``
490 - An alternate form of the sliced VBI data payload used when 36
491 lines of sliced VBI data are present. No line masks are provided
492 in this form of the payload; all valid line mask bits are
493 implicitly set.
494 * - }
495 -
496
497 .. _v4l2-mpeg-vbi-fmt-ivtv-magic:
498
499 Magic Constants for struct v4l2_mpeg_vbi_fmt_ivtv magic field
500 -------------------------------------------------------------
501
502 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
503
504 .. flat-table::
505 :header-rows: 1
506 :stub-columns: 0
507 :widths: 3 1 4
508
509 * - Defined Symbol
510 - Value
511 - Description
512 * - ``V4L2_MPEG_VBI_IVTV_MAGIC0``
513 - "itv0"
514 - Indicates the ``itv0`` member of the union in struct
515 :c:type:`v4l2_mpeg_vbi_fmt_ivtv` is
516 valid.
517 * - ``V4L2_MPEG_VBI_IVTV_MAGIC1``
518 - "ITV0"
519 - Indicates the ``ITV0`` member of the union in struct
520 :c:type:`v4l2_mpeg_vbi_fmt_ivtv` is
521 valid and that 36 lines of sliced VBI data are present.
522
523
524 .. c:type:: v4l2_mpeg_vbi_itv0
525
526 .. c:type:: v4l2_mpeg_vbi_ITV0
527
528 structs v4l2_mpeg_vbi_itv0 and v4l2_mpeg_vbi_ITV0
529 -------------------------------------------------
530
531 .. raw:: latex
532
533 \footnotesize
534
535 .. tabularcolumns:: |p{4.6cm}|p{2.0cm}|p{10.7cm}|
536
537 .. flat-table::
538 :header-rows: 0
539 :stub-columns: 0
540 :widths: 1 1 2
541
542 * - __le32
543 - ``linemask``\ [2]
544 - Bitmasks indicating the VBI service lines present. These
545 ``linemask`` values are stored in little endian byte order in the
546 MPEG stream. Some reference ``linemask`` bit positions with their
547 corresponding VBI line number and video field are given below.
548 b\ :sub:`0` indicates the least significant bit of a ``linemask``
549 value:
550
551
552 ::
553
554 linemask[0] b0: line 6 first field
555 linemask[0] b17: line 23 first field
556 linemask[0] b18: line 6 second field
557 linemask[0] b31: line 19 second field
558 linemask[1] b0: line 20 second field
559 linemask[1] b3: line 23 second field
560 linemask[1] b4-b31: unused and set to 0
561 * - struct
562 :c:type:`v4l2_mpeg_vbi_itv0_line`
563 - ``line``\ [35]
564 - This is a variable length array that holds from 1 to 35 lines of
565 sliced VBI data. The sliced VBI data lines present correspond to
566 the bits set in the ``linemask`` array, starting from b\ :sub:`0`
567 of ``linemask``\ [0] up through b\ :sub:`31` of ``linemask``\ [0],
568 and from b\ :sub:`0` of ``linemask``\ [1] up through b\ :sub:`3` of
569 ``linemask``\ [1]. ``line``\ [0] corresponds to the first bit
570 found set in the ``linemask`` array, ``line``\ [1] corresponds to
571 the second bit found set in the ``linemask`` array, etc. If no
572 ``linemask`` array bits are set, then ``line``\ [0] may contain
573 one line of unspecified data that should be ignored by
574 applications.
575
576 .. raw:: latex
577
578 \normalsize
579
580 .. _v4l2-mpeg-vbi-itv0-1:
581
582 struct v4l2_mpeg_vbi_ITV0
583 -------------------------
584
585 .. tabularcolumns:: |p{5.2cm}|p{2.4cm}|p{9.7cm}|
586
587 .. flat-table::
588 :header-rows: 0
589 :stub-columns: 0
590 :widths: 1 1 2
591
592 * - struct
593 :c:type:`v4l2_mpeg_vbi_itv0_line`
594 - ``line``\ [36]
595 - A fixed length array of 36 lines of sliced VBI data. ``line``\ [0]
596 through ``line``\ [17] correspond to lines 6 through 23 of the
597 first field. ``line``\ [18] through ``line``\ [35] corresponds to
598 lines 6 through 23 of the second field.
599
600
601 .. c:type:: v4l2_mpeg_vbi_itv0_line
602
603 struct v4l2_mpeg_vbi_itv0_line
604 ------------------------------
605
606 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
607
608 .. flat-table::
609 :header-rows: 0
610 :stub-columns: 0
611 :widths: 1 1 2
612
613 * - __u8
614 - ``id``
615 - A line identifier value from
616 :ref:`ITV0-Line-Identifier-Constants` that indicates the type of
617 sliced VBI data stored on this line.
618 * - __u8
619 - ``data``\ [42]
620 - The sliced VBI data for the line.
621
622
623 .. _ITV0-Line-Identifier-Constants:
624
625 Line Identifiers for struct v4l2_mpeg_vbi_itv0_line id field
626 ------------------------------------------------------------
627
628 .. tabularcolumns:: |p{7.0cm}|p{1.8cm}|p{8.5cm}|
629
630 .. flat-table::
631 :header-rows: 1
632 :stub-columns: 0
633 :widths: 3 1 4
634
635 * - Defined Symbol
636 - Value
637 - Description
638 * - ``V4L2_MPEG_VBI_IVTV_TELETEXT_B``
639 - 1
640 - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
641 description of the line payload.
642 * - ``V4L2_MPEG_VBI_IVTV_CAPTION_525``
643 - 4
644 - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
645 description of the line payload.
646 * - ``V4L2_MPEG_VBI_IVTV_WSS_625``
647 - 5
648 - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
649 description of the line payload.
650 * - ``V4L2_MPEG_VBI_IVTV_VPS``
651 - 7
652 - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
653 description of the line payload.
654
655
656 .. [#f1]
657 According to :ref:`ETS 300 706 <ets300706>` lines 6-22 of the first
658 field and lines 5-22 of the second field may carry Teletext data.
659
660 .. [#f2]
661 See also :ref:`vbi-525` and :ref:`vbi-625`.
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