1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _sliced:
5
6*************************
7Sliced VBI Data Interface
8*************************
9
10VBI stands for Vertical Blanking Interval, a gap in the sequence of
11lines of an analog video signal. During VBI no picture information is
12transmitted, allowing some time while the electron beam of a cathode ray
13tube TV returns to the top of the screen.
14
15Sliced VBI devices use hardware to demodulate data transmitted in the
16VBI. V4L2 drivers shall *not* do this by software, see also the
17:ref:`raw VBI interface <raw-vbi>`. The data is passed as short
18packets of fixed size, covering one scan line each. The number of
19packets per video frame is variable.
20
21Sliced VBI capture and output devices are accessed through the same
22character special files as raw VBI devices. When a driver supports both
23interfaces, the default function of a ``/dev/vbi`` device is *raw* VBI
24capturing or output, and the sliced VBI function is only available after
25calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl as defined
26below. Likewise a ``/dev/video`` device may support the sliced VBI API,
27however the default function here is video capturing or output.
28Different file descriptors must be used to pass raw and sliced VBI data
29simultaneously, if this is supported by the driver.
30
31Querying Capabilities
32=====================
33
34Devices supporting the sliced VBI capturing or output API set the
35``V4L2_CAP_SLICED_VBI_CAPTURE`` or ``V4L2_CAP_SLICED_VBI_OUTPUT`` flag
36respectively, in the ``capabilities`` field of struct
37:c:type:`v4l2_capability` returned by the
38:ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
39read/write or streaming :ref:`I/O methods <io>` must be
40supported. Sliced VBI devices may have a tuner or modulator.
41
42Supplemental Functions
43======================
44
45Sliced VBI devices shall support :ref:`video input or output <video>`
46and :ref:`tuner or modulator <tuner>` ioctls if they have these
47capabilities, and they may support :ref:`control` ioctls.
48The :ref:`video standard <standard>` ioctls provide information vital
49to program a sliced VBI device, therefore must be supported.
50
51.. _sliced-vbi-format-negotitation:
52
53Sliced VBI Format Negotiation
54=============================
55
56To find out which data services are supported by the hardware
57applications can call the
58:ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl.
59All drivers implementing the sliced VBI interface must support this
60ioctl. The results may differ from those of the
61:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl when the number of VBI
62lines the hardware can capture or output per frame, or the number of
63services it can identify on a given line are limited. For example on PAL
64line 16 the hardware may be able to look for a VPS or Teletext signal,
65but not both at the same time.
66
67To 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``
72member, a struct
73:c:type:`v4l2_sliced_vbi_format`.
74
75Applications can request different parameters by initializing or
76modifying the ``fmt.sliced`` member and calling the
77:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with a pointer to the
78struct :c:type:`v4l2_format` structure.
79
80The sliced VBI API is more complicated than the raw VBI API because the
81hardware must be told which VBI service to expect on each scan line. Not
82all services may be supported by the hardware on all lines (this is
83especially true for VBI output where Teletext is often unsupported and
84other services can only be inserted in one specific line). In many
85cases, however, it is sufficient to just set the ``service_set`` field
86to the required services and let the driver fill the ``service_lines``
87array according to hardware capabilities. Only if more precise control
88is needed should the programmer set the ``service_lines`` array
89explicitly.
90
91The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl modifies the parameters
92according to hardware capabilities. When the driver allocates resources
93at this point, it may return an ``EBUSY`` error code if the required
94resources are temporarily unavailable. Other resource allocation points
95which 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
102struct 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
211Sliced 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
268Drivers may return an ``EINVAL`` error code when applications attempt to
269read or write data without prior format negotiation, after switching the
270video standard (which may invalidate the negotiated VBI parameters) and
271after switching the video input (which may change the video standard as
272a side effect). The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl may
273return an ``EBUSY`` error code when applications attempt to change the
274format 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
281V4L2_SLICED_WSS_625 payload
282~~~~~~~~~~~~~~~~~~~~~~~~~~~
283
284The 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
294Reading and writing sliced VBI data
295===================================
296
297A single :c:func:`read()` or :c:func:`write()`
298call must pass all data belonging to one video frame. That is an array
299of struct :c:type:`v4l2_sliced_vbi_data` structures with one or
300more elements and a total size not exceeding ``io_size`` bytes. Likewise
301in streaming I/O mode one buffer of ``io_size`` bytes must contain data
302of one video frame. The ``id`` of unused
303struct :c:type:`v4l2_sliced_vbi_data` elements must be zero.
304
305.. c:type:: v4l2_sliced_vbi_data
306
307struct 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
350Packets are always passed in ascending line number order, without
351duplicate line numbers. The :c:func:`write()` function and
352the :ref:`VIDIOC_QBUF` ioctl must return an ``EINVAL``
353error code when applications violate this rule. They must also return an
354EINVAL error code when applications pass an incorrect field or line
355number, or a combination of ``field``, ``line`` and ``id`` which has not
356been 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
358unknown the driver must pass the packets in transmitted order. The
359driver can insert empty packets with ``id`` set to zero anywhere in the
360packet array.
361
362To assure synchronization and to distinguish from frame dropping, when a
363captured frame does not carry any of the requested data services drivers
364must pass one or more empty packets. When an application fails to pass
365VBI data in time for output, the driver must output the last VPS and WSS
366packet again, and disable the output of Closed Caption and Teletext
367data, or output data which is ignored by Closed Caption and Teletext
368decoders.
369
370A sliced VBI device may support :ref:`read/write <rw>` and/or
371streaming (:ref:`memory mapping <mmap>` and/or
372:ref:`user pointer <userp>`) I/O. The latter bears the possibility of
373synchronizing video and VBI data by using buffer timestamps.
374
375Sliced VBI Data in MPEG Streams
376===============================
377
378If a device can produce an MPEG output stream, it may be capable of
379providing
380:ref:`negotiated sliced VBI services <sliced-vbi-format-negotitation>`
381as data embedded in the MPEG stream. Users or applications control this
382sliced VBI data insertion with the
383:ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
384control.
385
386If the driver does not provide the
387:ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
388control, or only allows that control to be set to
389:ref:`V4L2_MPEG_STREAM_VBI_FMT_NONE <v4l2-mpeg-stream-vbi-fmt>`,
390then the device cannot embed sliced VBI data in the MPEG stream.
391
392The
393:ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
394control does not implicitly set the device driver to capture nor cease
395capturing sliced VBI data. The control only indicates to embed sliced
396VBI data in the MPEG stream, if an application has negotiated sliced VBI
397service be captured.
398
399It may also be the case that a device can embed sliced VBI data in only
400certain types of MPEG streams: for example in an MPEG-2 PS but not an
401MPEG-2 TS. In this situation, if sliced VBI data insertion is requested,
402the sliced VBI data will be embedded in MPEG stream types when
403supported, and silently omitted from MPEG stream types where sliced VBI
404data insertion is not supported by the device.
405
406The following subsections specify the format of the embedded sliced VBI
407data.
408
409MPEG Stream Embedded, Sliced VBI Data Format: NONE
410--------------------------------------------------
411
412The
413:ref:`V4L2_MPEG_STREAM_VBI_FMT_NONE <v4l2-mpeg-stream-vbi-fmt>`
414embedded sliced VBI format shall be interpreted by drivers as a control
415to cease embedding sliced VBI data in MPEG streams. Neither the device
416nor driver shall insert "empty" embedded sliced VBI data packets in the
417MPEG stream when this format is set. No MPEG stream data structures are
418specified for this format.
419
420MPEG Stream Embedded, Sliced VBI Data Format: IVTV
421--------------------------------------------------
422
423The
424:ref:`V4L2_MPEG_STREAM_VBI_FMT_IVTV <v4l2-mpeg-stream-vbi-fmt>`
425embedded sliced VBI format, when supported, indicates to the driver to
426embed up to 36 lines of sliced VBI data per frame in an MPEG-2 *Private
427Stream 1 PES* packet encapsulated in an MPEG-2 *Program Pack* in the
428MPEG stream.
429
430*Historical context*: This format specification originates from a
431custom, embedded, sliced VBI data format used by the ``ivtv`` driver.
432This format has already been informally specified in the kernel sources
433in the file ``Documentation/userspace-api/media/drivers/cx2341x-uapi.rst`` . The
434maximum size of the payload and other aspects of this format are driven
435by the CX23415 MPEG decoder's capabilities and limitations with respect
436to extracting, decoding, and displaying sliced VBI data embedded within
437an MPEG stream.
438
439This format's use is *not* exclusive to the ``ivtv`` driver *nor*
440exclusive to CX2341x devices, as the sliced VBI data packet insertion
441into 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
443this format as well.
444
445The following definitions specify the payload of the MPEG-2 *Private
446Stream 1 PES* packets that contain sliced VBI data when
447:ref:`V4L2_MPEG_STREAM_VBI_FMT_IVTV <v4l2-mpeg-stream-vbi-fmt>`
448is set. (The MPEG-2 *Private Stream 1 PES* packet header and
449encapsulating MPEG-2 *Program Pack* header are not detailed here. Please
450refer to the MPEG-2 specifications for details on those packet headers.)
451
452The payload of the MPEG-2 *Private Stream 1 PES* packets that contain
453sliced VBI data is specified by struct
454:c:type:`v4l2_mpeg_vbi_fmt_ivtv`. The
455payload is variable length, depending on the actual number of lines of
456sliced VBI data present in a video frame. The payload may be padded at
457the end with unspecified fill bytes to align the end of the payload to a
4584-byte boundary. The payload shall never exceed 1552 bytes (2 fields
459with 18 lines/field with 43 bytes of data/line and a 4 byte magic
460number).
461
462.. c:type:: v4l2_mpeg_vbi_fmt_ivtv
463
464struct 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	implcitly set.
494    * - }
495      -
496
497.. _v4l2-mpeg-vbi-fmt-ivtv-magic:
498
499Magic 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
528structs 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
582struct 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
603struct 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
625Line 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`.
662