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Based on kernel version 4.1. Page generated on 2015-06-28 12:11 EST.

1	  <title>Sliced VBI Data Interface</title>
2	
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>
7	
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>
14	
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>
25	
26	  <section>
27	    <title>Querying Capabilities</title>
28	
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>
38	
39	  <section>
40	    <title>Supplemental Functions</title>
41	
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>
50	
51	  <section id="sliced-vbi-format-negotitation">
52	    <title>Sliced VBI Format Negotiation</title>
53	
54	    <para>To find out which data services are supported by the
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>
62	
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>
69	
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>
74	
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>
86	
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>
94	
95	    <table frame="none" pgwide="1" id="v4l2-sliced-vbi-format">
96	      <title>struct
97	<structname>v4l2_sliced_vbi_format</structname></title>
98	      <tgroup cols="5">
99		<colspec colname="c1" colwidth="3*" />
100		<colspec colname="c2" colwidth="3*" />
101		<colspec colname="c3" colwidth="2*" />
102		<colspec colname="c4" colwidth="2*" />
103		<colspec colname="c5" colwidth="2*" />
104		<spanspec namest="c3" nameend="c5" spanname="hspan" />
105		<tbody valign="top">
106		  <row>
107		    <entry>__u32</entry>
108		    <entry><structfield>service_set</structfield></entry>
109		    <entry spanname="hspan"><para>If
110	<structfield>service_set</structfield> is non-zero when passed with
111	&VIDIOC-S-FMT; or &VIDIOC-TRY-FMT;, the
112	<structfield>service_lines</structfield> array will be filled by the
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&nbsp;300&nbsp;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.
189	The <constant>V4L2_VBI_ITU_525_F1_START</constant>,
190	<constant>V4L2_VBI_ITU_525_F2_START</constant>,
191	<constant>V4L2_VBI_ITU_625_F1_START</constant> and
192	<constant>V4L2_VBI_ITU_625_F2_START</constant> defines give the start
193	line numbers for each field for each 525 or 625 line format as a
194	convenience.  Don't forget that ITU line numbering starts at 1, not 0.
195	</entry>
196		  </row>
197		  <row>
198		    <entry>__u32</entry>
199		    <entry><structfield>io_size</structfield></entry>
200		    <entry spanname="hspan">Maximum number of bytes passed by
201	one &func-read; or &func-write; call, and the buffer size in bytes for
202	the &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. Drivers set this field to
203	the size of &v4l2-sliced-vbi-data; times the number of non-zero
204	elements in the returned <structfield>service_lines</structfield>
205	array (that is the number of lines potentially carrying data).</entry>
206		  </row>
207		  <row>
208		    <entry>__u32</entry>
209		    <entry><structfield>reserved</structfield>[2]</entry>
210		    <entry spanname="hspan">This array is reserved for future
211	extensions. Applications and drivers must set it to zero.</entry>
212		  </row>
213		</tbody>
214	      </tgroup>
215	    </table>
216	
217	    <!-- See also vidioc-g-sliced-vbi-cap.sgml -->
218	    <table frame="none" pgwide="1" id="vbi-services2">
219	      <title>Sliced VBI services</title>
220	      <tgroup cols="5">
221		<colspec colname="c1" colwidth="2*" />
222		<colspec colname="c2" colwidth="1*" />
223		<colspec colname="c3" colwidth="1*" />
224		<colspec colname="c4" colwidth="2*" />
225		<colspec colname="c5" colwidth="2*" />
226		<spanspec namest="c3" nameend="c5" spanname="rlp" />
227		<thead>
228		  <row>
229		    <entry>Symbol</entry>
230		    <entry>Value</entry>
231		    <entry>Reference</entry>
232		    <entry>Lines, usually</entry>
233		    <entry>Payload</entry>
234		  </row>
235		</thead>
236		<tbody valign="top">
237		  <row>
238		    <entry><constant>V4L2_SLICED_TELETEXT_B</constant>
239	(Teletext System B)</entry>
240		    <entry>0x0001</entry>
241		    <entry><xref linkend="ets300706" />, <xref linkend="itu653" /></entry>
242		    <entry>PAL/SECAM line 7-22, 320-335 (second field 7-22)</entry>
243		    <entry>Last 42 of the 45 byte Teletext packet, that is
244	without clock run-in and framing code, lsb first transmitted.</entry>
245		  </row>
246		  <row>
247		    <entry><constant>V4L2_SLICED_VPS</constant></entry>
248		    <entry>0x0400</entry>
249		    <entry><xref linkend="ets300231" /></entry>
250		    <entry>PAL line 16</entry>
251		    <entry>Byte number 3 to 15 according to Figure 9 of
252	ETS&nbsp;300&nbsp;231, lsb first transmitted.</entry>
253		  </row>
254		  <row>
255		    <entry><constant>V4L2_SLICED_CAPTION_525</constant></entry>
256		    <entry>0x1000</entry>
257		    <entry><xref linkend="cea608" /></entry>
258		    <entry>NTSC line 21, 284 (second field 21)</entry>
259		    <entry>Two bytes in transmission order, including parity
260	bit, lsb first transmitted.</entry>
261		  </row>
262		  <row>
263		    <entry><constant>V4L2_SLICED_WSS_625</constant></entry>
264		    <entry>0x4000</entry>
265		    <entry><xref linkend="itu1119" />, <xref linkend="en300294" /></entry>
266		    <entry>PAL/SECAM line 23</entry>
267		    <entry><screen>
268	Byte         0                 1
269	      msb         lsb  msb           lsb
270	 Bit  7 6 5 4 3 2 1 0  x x 13 12 11 10 9
271	</screen></entry>
272		  </row>
273		  <row>
274		    <entry><constant>V4L2_SLICED_VBI_525</constant></entry>
275		    <entry>0x1000</entry>
276		    <entry spanname="rlp">Set of services applicable to 525
277	line systems.</entry>
278		  </row>
279		  <row>
280		    <entry><constant>V4L2_SLICED_VBI_625</constant></entry>
281		    <entry>0x4401</entry>
282		    <entry spanname="rlp">Set of services applicable to 625
283	line systems.</entry>
284		  </row>
285		</tbody>
286	      </tgroup>
287	    </table>
288	
289	    <para>Drivers may return an &EINVAL; when applications attempt to
290	read or write data without prior format negotiation, after switching
291	the video standard (which may invalidate the negotiated VBI
292	parameters) and after switching the video input (which may change the
293	video standard as a side effect). The &VIDIOC-S-FMT; ioctl may return
294	an &EBUSY; when applications attempt to change the format while i/o is
295	in progress (between a &VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; call,
296	and after the first &func-read; or &func-write; call).</para>
297	  </section>
298	
299	  <section>
300	    <title>Reading and writing sliced VBI data</title>
301	
302	    <para>A single &func-read; or &func-write; call must pass all data
303	belonging to one video frame. That is an array of
304	<structname>v4l2_sliced_vbi_data</structname> structures with one or
305	more elements and a total size not exceeding
306	<structfield>io_size</structfield> bytes. Likewise in streaming I/O
307	mode one buffer of <structfield>io_size</structfield> bytes must
308	contain data of one video frame. The <structfield>id</structfield> of
309	unused <structname>v4l2_sliced_vbi_data</structname> elements must be
310	zero.</para>
311	
312	    <table frame="none" pgwide="1" id="v4l2-sliced-vbi-data">
313	      <title>struct
314	<structname>v4l2_sliced_vbi_data</structname></title>
315	      <tgroup cols="3">
316		&cs-def;
317		<tbody valign="top">
318		  <row>
319		    <entry>__u32</entry>
320		    <entry><structfield>id</structfield></entry>
321		    <entry>A flag from <xref linkend="vbi-services" />
322	identifying the type of data in this packet. Only a single bit must be
323	set. When the <structfield>id</structfield> of a captured packet is
324	zero, the packet is empty and the contents of other fields are
325	undefined. Applications shall ignore empty packets. When the
326	<structfield>id</structfield> of a packet for output is zero the
327	contents of the <structfield>data</structfield> field are undefined
328	and the driver must no longer insert data on the requested
329	<structfield>field</structfield> and
330	<structfield>line</structfield>.</entry>
331		  </row>
332		  <row>
333		    <entry>__u32</entry>
334		    <entry><structfield>field</structfield></entry>
335		    <entry>The video field number this data has been captured
336	from, or shall be inserted at. <constant>0</constant> for the first
337	field, <constant>1</constant> for the second field.</entry>
338		  </row>
339		  <row>
340		    <entry>__u32</entry>
341		    <entry><structfield>line</structfield></entry>
342		    <entry>The field (as opposed to frame) line number this
343	data has been captured from, or shall be inserted at. See <xref
344		    linkend="vbi-525" /> and <xref linkend="vbi-625" /> for valid
345	values. Sliced VBI capture devices can set the line number of all
346	packets to <constant>0</constant> if the hardware cannot reliably
347	identify scan lines. The field number must always be valid.</entry>
348		  </row>
349		  <row>
350		    <entry>__u32</entry>
351		    <entry><structfield>reserved</structfield></entry>
352		    <entry>This field is reserved for future extensions.
353	Applications and drivers must set it to zero.</entry>
354		  </row>
355		  <row>
356		    <entry>__u8</entry>
357		    <entry><structfield>data</structfield>[48]</entry>
358		    <entry>The packet payload. See <xref
359		    linkend="vbi-services" /> for the contents and number of
360	bytes passed for each data type. The contents of padding bytes at the
361	end of this array are undefined, drivers and applications shall ignore
362	them.</entry>
363		  </row>
364		</tbody>
365	      </tgroup>
366	    </table>
367	
368	    <para>Packets are always passed in ascending line number order,
369	without duplicate line numbers. The &func-write; function and the
370	&VIDIOC-QBUF; ioctl must return an &EINVAL; when applications violate
371	this rule. They must also return an &EINVAL; when applications pass an
372	incorrect field or line number, or a combination of
373	<structfield>field</structfield>, <structfield>line</structfield> and
374	<structfield>id</structfield> which has not been negotiated with the
375	&VIDIOC-G-FMT; or &VIDIOC-S-FMT; ioctl. When the line numbers are
376	unknown the driver must pass the packets in transmitted order. The
377	driver can insert empty packets with <structfield>id</structfield> set
378	to zero anywhere in the packet array.</para>
379	
380	    <para>To assure synchronization and to distinguish from frame
381	dropping, when a captured frame does not carry any of the requested
382	data services drivers must pass one or more empty packets. When an
383	application fails to pass VBI data in time for output, the driver
384	must output the last VPS and WSS packet again, and disable the output
385	of Closed Caption and Teletext data, or output data which is ignored
386	by Closed Caption and Teletext decoders.</para>
387	
388	    <para>A sliced VBI device may support <link
389	linkend="rw">read/write</link> and/or streaming (<link
390	linkend="mmap">memory mapping</link> and/or <link linkend="userp">user
391	pointer</link>) I/O. The latter bears the possibility of synchronizing
392	video and VBI data by using buffer timestamps.</para>
393	
394	  </section>
395	
396	  <section>
397	    <title>Sliced VBI Data in MPEG Streams</title>
398	
399	    <para>If a device can produce an MPEG output stream, it may be
400	capable of providing <link
401	linkend="sliced-vbi-format-negotitation">negotiated sliced VBI
402	services</link> as data embedded in the MPEG stream.  Users or
403	applications control this sliced VBI data insertion with the <link
404	linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link>
405	control.</para>
406	
407	    <para>If the driver does not provide the <link
408	linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link>
409	control, or only allows that control to be set to <link
410	linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
411	V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link>, then the device
412	cannot embed sliced VBI data in the MPEG stream.</para>
413	
414	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt">
415	V4L2_CID_MPEG_STREAM_VBI_FMT</link> control does not implicitly set
416	the device driver to capture nor cease capturing sliced VBI data.  The
417	control only indicates to embed sliced VBI data in the MPEG stream, if
418	an application has negotiated sliced VBI service be captured.</para>
419	
420	    <para>It may also be the case that a device can embed sliced VBI
421	data in only certain types of MPEG streams: for example in an MPEG-2
422	PS but not an MPEG-2 TS.  In this situation, if sliced VBI data
423	insertion is requested, the sliced VBI data will be embedded in MPEG
424	stream types when supported, and silently omitted from MPEG stream
425	types where sliced VBI data insertion is not supported by the device.
426	</para>
427	
428	    <para>The following subsections specify the format of the
429	embedded sliced VBI data.</para>
430	
431	  <section>
432	    <title>MPEG Stream Embedded, Sliced VBI Data Format: NONE</title>
433	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
434	V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link> embedded sliced VBI
435	format shall be interpreted by drivers as a control to cease
436	embedding sliced VBI data in MPEG streams.  Neither the device nor
437	driver shall insert "empty" embedded sliced VBI data packets in the
438	MPEG stream when this format is set.  No MPEG stream data structures
439	are specified for this format.</para>
440	  </section>
441	
442	  <section>
443	    <title>MPEG Stream Embedded, Sliced VBI Data Format: IVTV</title>
444	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
445	V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> embedded sliced VBI
446	format, when supported, indicates to the driver to embed up to 36
447	lines of sliced VBI data per frame in an MPEG-2 <emphasis>Private
448	Stream 1 PES</emphasis> packet encapsulated in an MPEG-2 <emphasis>
449	Program Pack</emphasis> in the MPEG stream.</para>
450	
451	    <para><emphasis>Historical context</emphasis>: This format
452	specification originates from a custom, embedded, sliced VBI data
453	format used by the <filename>ivtv</filename> driver.  This format
454	has already been informally specified in the kernel sources in the
455	file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>
456	.  The maximum size of the payload and other aspects of this format
457	are driven by the CX23415 MPEG decoder's capabilities and limitations
458	with respect to extracting, decoding, and displaying sliced VBI data
459	embedded within an MPEG stream.</para>
460	
461	    <para>This format's use is <emphasis>not</emphasis> exclusive to
462	the <filename>ivtv</filename> driver <emphasis>nor</emphasis>
463	exclusive to CX2341x devices, as the sliced VBI data packet insertion
464	into the MPEG stream is implemented in driver software.  At least the
465	<filename>cx18</filename> driver provides sliced VBI data insertion
466	into an MPEG-2 PS in this format as well.</para>
467	
468	    <para>The following definitions specify the payload of the
469	MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packets that contain
470	sliced VBI data when <link linkend="v4l2-mpeg-stream-vbi-fmt">
471	<constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> is set.
472	(The MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packet header
473	and encapsulating MPEG-2 <emphasis>Program Pack</emphasis> header are
474	not detailed here.  Please refer to the MPEG-2 specifications for
475	details on those packet headers.)</para>
476	
477	    <para>The payload of the MPEG-2 <emphasis>Private Stream 1 PES
478	</emphasis> packets that contain sliced VBI data is specified by
479	&v4l2-mpeg-vbi-fmt-ivtv;.  The payload is variable
480	length, depending on the actual number of lines of sliced VBI data
481	present in a video frame.  The payload may be padded at the end with
482	unspecified fill bytes to align the end of the payload to a 4-byte
483	boundary.  The payload shall never exceed 1552 bytes (2 fields with
484	18 lines/field with 43 bytes of data/line and a 4 byte magic number).
485	</para>
486	
487	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv">
488	      <title>struct <structname>v4l2_mpeg_vbi_fmt_ivtv</structname>
489	      </title>
490	      <tgroup cols="4">
491		&cs-ustr;
492		<tbody valign="top">
493		  <row>
494		    <entry>__u8</entry>
495		    <entry><structfield>magic</structfield>[4]</entry>
496		    <entry></entry>
497		    <entry>A "magic" constant from <xref
498		    linkend="v4l2-mpeg-vbi-fmt-ivtv-magic" /> that indicates
499	this is a valid sliced VBI data payload and also indicates which
500	member of the anonymous union, <structfield>itv0</structfield> or
501	<structfield>ITV0</structfield>, to use for the payload data.</entry>
502		  </row>
503		  <row>
504		    <entry>union</entry>
505		    <entry>(anonymous)</entry>
506		  </row>
507		  <row>
508		    <entry></entry>
509		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0">
510		      <structname>v4l2_mpeg_vbi_itv0</structname></link>
511		    </entry>
512		    <entry><structfield>itv0</structfield></entry>
513		    <entry>The primary form of the sliced VBI data payload
514	that contains anywhere from 1 to 35 lines of sliced VBI data.
515	Line masks are provided in this form of the payload indicating
516	which VBI lines are provided.</entry>
517		  </row>
518		  <row>
519		    <entry></entry>
520		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-1">
521		      <structname>v4l2_mpeg_vbi_ITV0</structname></link>
522		    </entry>
523		    <entry><structfield>ITV0</structfield></entry>
524		    <entry>An alternate form of the sliced VBI data payload
525	used when 36 lines of sliced VBI data are present.  No line masks are
526	provided in this form of the payload; all valid line mask bits are
527	implcitly set.</entry>
528		  </row>
529		</tbody>
530	      </tgroup>
531	    </table>
532	
533	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv-magic">
534	      <title>Magic Constants for &v4l2-mpeg-vbi-fmt-ivtv;
535		<structfield>magic</structfield> field</title>
536	      <tgroup cols="3">
537		&cs-def;
538		<thead>
539		  <row>
540		    <entry align="left">Defined Symbol</entry>
541		    <entry align="left">Value</entry>
542		    <entry align="left">Description</entry>
543		  </row>
544		</thead>
545		<tbody valign="top">
546		  <row>
547		    <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC0</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.</entry>
552		  </row>
553		  <row>
554		    <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC1</constant>
555		    </entry>
556		    <entry>"ITV0"</entry>
557		    <entry>Indicates the <structfield>ITV0</structfield>
558	member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid and
559	that 36 lines of sliced VBI data are present.</entry>
560		  </row>
561		</tbody>
562	      </tgroup>
563	    </table>
564	
565	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0">
566	      <title>struct <structname>v4l2_mpeg_vbi_itv0</structname>
567	      </title>
568	      <tgroup cols="3">
569		&cs-str;
570		<tbody valign="top">
571		  <row>
572		    <entry>__le32</entry>
573		    <entry><structfield>linemask</structfield>[2]</entry>
574		    <entry><para>Bitmasks indicating the VBI service lines
575	present.  These <structfield>linemask</structfield> values are stored
576	in little endian byte order in the MPEG stream.  Some reference
577	<structfield>linemask</structfield> bit positions with their
578	corresponding VBI line number and video field are given below.
579	b<subscript>0</subscript> indicates the least significant bit of a
580	<structfield>linemask</structfield> value:<screen>
581	<structfield>linemask</structfield>[0] b<subscript>0</subscript>:		line  6		first field
582	<structfield>linemask</structfield>[0] b<subscript>17</subscript>:		line 23		first field
583	<structfield>linemask</structfield>[0] b<subscript>18</subscript>:		line  6		second field
584	<structfield>linemask</structfield>[0] b<subscript>31</subscript>:		line 19		second field
585	<structfield>linemask</structfield>[1] b<subscript>0</subscript>:		line 20		second field
586	<structfield>linemask</structfield>[1] b<subscript>3</subscript>:		line 23		second field
587	<structfield>linemask</structfield>[1] b<subscript>4</subscript>-b<subscript>31</subscript>:	unused and set to 0</screen></para></entry>
588		  </row>
589		  <row>
590		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line">
591		      <structname>v4l2_mpeg_vbi_itv0_line</structname></link>
592		    </entry>
593		    <entry><structfield>line</structfield>[35]</entry>
594		    <entry>This is a variable length array that holds from 1
595	to 35 lines of sliced VBI data.  The sliced VBI data lines present
596	correspond to the bits set in the <structfield>linemask</structfield>
597	array, starting from b<subscript>0</subscript> of <structfield>
598	linemask</structfield>[0] up through b<subscript>31</subscript> of
599	<structfield>linemask</structfield>[0], and from b<subscript>0
600	</subscript> of <structfield>linemask</structfield>[1] up through b
601	<subscript>3</subscript> of <structfield>linemask</structfield>[1].
602	<structfield>line</structfield>[0] corresponds to the first bit
603	found set in the <structfield>linemask</structfield> array,
604	<structfield>line</structfield>[1] corresponds to the second bit
605	found set in the <structfield>linemask</structfield> array, etc.
606	If no <structfield>linemask</structfield> array bits are set, then
607	<structfield>line</structfield>[0] may contain one line of
608	unspecified data that should be ignored by applications.</entry>
609		  </row>
610		</tbody>
611	      </tgroup>
612	    </table>
613	
614	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-1">
615	      <title>struct <structname>v4l2_mpeg_vbi_ITV0</structname>
616	      </title>
617	      <tgroup cols="3">
618		&cs-str;
619		<tbody valign="top">
620		  <row>
621		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line">
622		      <structname>v4l2_mpeg_vbi_itv0_line</structname></link>
623		    </entry>
624		    <entry><structfield>line</structfield>[36]</entry>
625		    <entry>A fixed length array of 36 lines of sliced VBI
626	data.  <structfield>line</structfield>[0] through <structfield>line
627	</structfield>[17] correspond to lines 6 through 23 of the
628	first field.  <structfield>line</structfield>[18] through
629	<structfield>line</structfield>[35] corresponds to lines 6
630	through 23 of the second field.</entry>
631		  </row>
632		</tbody>
633	      </tgroup>
634	    </table>
635	
636	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-line">
637	      <title>struct <structname>v4l2_mpeg_vbi_itv0_line</structname>
638	      </title>
639	      <tgroup cols="3">
640		&cs-str;
641		<tbody valign="top">
642		  <row>
643		    <entry>__u8</entry>
644		    <entry><structfield>id</structfield></entry>
645		    <entry>A line identifier value from
646	<xref linkend="ITV0-Line-Identifier-Constants" /> that indicates
647	the type of sliced VBI data stored on this line.</entry>
648		  </row>
649		  <row>
650		    <entry>__u8</entry>
651		    <entry><structfield>data</structfield>[42]</entry>
652		    <entry>The sliced VBI data for the line.</entry>
653		  </row>
654		</tbody>
655	      </tgroup>
656	    </table>
657	
658	    <table frame="none" pgwide="1" id="ITV0-Line-Identifier-Constants">
659	      <title>Line Identifiers for struct <link
660	      linkend="v4l2-mpeg-vbi-itv0-line"><structname>
661	v4l2_mpeg_vbi_itv0_line</structname></link> <structfield>id
662	</structfield> field</title>
663	      <tgroup cols="3">
664		&cs-def;
665		<thead>
666		  <row>
667		    <entry align="left">Defined Symbol</entry>
668		    <entry align="left">Value</entry>
669		    <entry align="left">Description</entry>
670		  </row>
671		</thead>
672		<tbody valign="top">
673		  <row>
674		    <entry><constant>V4L2_MPEG_VBI_IVTV_TELETEXT_B</constant>
675		    </entry>
676		    <entry>1</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_CAPTION_525</constant>
682		    </entry>
683		    <entry>4</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_WSS_625</constant>
689		    </entry>
690		    <entry>5</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		  <row>
695		    <entry><constant>V4L2_MPEG_VBI_IVTV_VPS</constant>
696		    </entry>
697		    <entry>7</entry>
698		    <entry>Refer to <link linkend="vbi-services2">
699	Sliced VBI services</link> for a description of the line payload.</entry>
700		  </row>
701		</tbody>
702	      </tgroup>
703	    </table>
704	
705	  </section>
706	  </section>
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