media/v4l/dev-sliced-vbi.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
7 Sliced VBI Data Interface
11 lines of an analog video signal. During VBI no picture information is
15 Sliced VBI devices use hardware to demodulate data transmitted in the
17 :ref:`raw VBI interface <raw-vbi>`. The data is passed as short
28 Different file descriptors must be used to pass raw and sliced VBI data
51 .. _sliced-vbi-format-negotitation:
56 To find out which data services are supported by the hardware
62 lines the hardware can capture or output per frame, or the number of
82 all services may be supported by the hardware on all lines (this is
103 -----------------------------
115 .. flat-table::
116     :header-rows:  0
117     :stub-columns: 0
120     * - __u16
121       - ``service_set``
122       - :cspan:`2`
124 	If ``service_set`` is non-zero when passed with
130 	a driver for the cx25840 video decoder sets lines 7-22 of both
140     * - __u16
141       - ``service_lines``\ [2][24]
142       - :cspan:`2`
144 	Applications initialize this array with sets of data services the
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
188     * - __u32
189       - ``io_size``
190       - :cspan:`2` Maximum number of bytes passed by one
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.
209 .. _vbi-services2:
212 -------------------
220 .. flat-table::
221     :header-rows:  1
222     :stub-columns: 0
225     * - Symbol
226       - Value
227       - Reference
228       - Lines, usually
229       - Payload
230     * - ``V4L2_SLICED_TELETEXT_B`` (Teletext System B)
231       - 0x0001
232       - :ref:`ets300706`,
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
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
250     * - ``V4L2_SLICED_WSS_625``
251       - 0x4000
252       - :ref:`itu1119`,
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.
269 read or write data without prior format negotiation, after switching the
279 .. _v4l2-sliced-wss-625-payload:
286            +-----+------------------+-----------------------+
288            +-----+--------+---------+-----------+-----------+
290            |     +-+-+-+--+--+-+-+--+--+-+--+---+---+--+-+--+
292            +-----+-+-+-+--+--+-+-+--+--+-+--+---+---+--+-+--+
294 Reading and writing sliced VBI data
298 call must pass all data belonging to one video frame. That is an array
301 in streaming I/O mode one buffer of ``io_size`` bytes must contain data
308 ---------------------------
312 .. flat-table::
313     :header-rows:  0
314     :stub-columns: 0
317     * - __u32
318       - ``id``
319       - A flag from :ref:`vbi-services` identifying the type of data in
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
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
337 	reliably identify scan lines. The field number must always be
339     * - __u32
340       - ``reserved``
341       - This field is reserved for future extensions. Applications and
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
363 captured frame does not carry any of the requested data services drivers
365 VBI data in time for output, the driver must output the last VPS and WSS
367 data, or output data which is ignored by Closed Caption and Teletext
373 synchronizing video and VBI data by using buffer timestamps.
375 Sliced VBI Data in MPEG Streams
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>`
387 :ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
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.
393 :ref:`V4L2_CID_MPEG_STREAM_VBI_FMT <v4l2-mpeg-stream-vbi-fmt>`
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
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
404 data insertion is not supported by the device.
407 data.
409 MPEG Stream Embedded, Sliced VBI Data Format: NONE
410 --------------------------------------------------
413 :ref:`V4L2_MPEG_STREAM_VBI_FMT_NONE <v4l2-mpeg-stream-vbi-fmt>`
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
420 MPEG Stream Embedded, Sliced VBI Data Format: IVTV
421 --------------------------------------------------
424 :ref:`V4L2_MPEG_STREAM_VBI_FMT_IVTV <v4l2-mpeg-stream-vbi-fmt>`
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
431 custom, embedded, sliced VBI data format used by the ``ivtv`` driver.
433 in the file ``Documentation/userspace-api/media/drivers/cx2341x-uapi.rst`` . The
436 to extracting, decoding, and displaying sliced VBI data embedded within
440 exclusive to CX2341x devices, as the sliced VBI data packet insertion
442 ``cx18`` driver provides sliced VBI data insertion into an MPEG-2 PS in
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.)
452 The payload of the MPEG-2 *Private Stream 1 PES* packets that contain
453 sliced VBI data is specified by struct
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
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
465 -----------------------------
469 .. flat-table::
470     :header-rows:  0
471     :stub-columns: 0
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
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
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
494     * - }
495       -
497 .. _v4l2-mpeg-vbi-fmt-ivtv-magic:
500 -------------------------------------------------------------
504 .. flat-table::
505     :header-rows:  1
506     :stub-columns: 0
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
517     * - ``V4L2_MPEG_VBI_IVTV_MAGIC1``
518       - "ITV0"
519       - Indicates the ``ITV0`` member of the union in struct
521 	valid and that 36 lines of sliced VBI data are present.
529 -------------------------------------------------
537 .. flat-table::
538     :header-rows:  0
539     :stub-columns: 0
542     * - __le32
543       - ``linemask``\ [2]
544       - Bitmasks indicating the VBI service lines present. These
560 	    linemask[1] b4-b31: unused and set to 0
561     * - struct
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
573 	one line of unspecified data that should be ignored by
580 .. _v4l2-mpeg-vbi-itv0-1:
583 -------------------------
587 .. flat-table::
588     :header-rows:  0
589     :stub-columns: 0
592     * - struct
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
598 	lines 6 through 23 of the second field.
604 ------------------------------
608 .. flat-table::
609     :header-rows:  0
610     :stub-columns: 0
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.
623 .. _ITV0-Line-Identifier-Constants:
626 ------------------------------------------------------------
630 .. flat-table::
631     :header-rows:  1
632     :stub-columns: 0
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
642     * - ``V4L2_MPEG_VBI_IVTV_CAPTION_525``
643       - 4
644       - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
646     * - ``V4L2_MPEG_VBI_IVTV_WSS_625``
647       - 5
648       - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
650     * - ``V4L2_MPEG_VBI_IVTV_VPS``
651       - 7
652       - Refer to :ref:`Sliced VBI services <vbi-services2>` for a
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.
661    See also :ref:`vbi-525` and :ref:`vbi-625`.