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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:02 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.</entry>
189		  </row>
190		  <row>
191		    <entry>__u32</entry>
192		    <entry><structfield>io_size</structfield></entry>
193		    <entry spanname="hspan">Maximum number of bytes passed by
194	one &func-read; or &func-write; call, and the buffer size in bytes for
195	the &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. Drivers set this field to
196	the size of &v4l2-sliced-vbi-data; times the number of non-zero
197	elements in the returned <structfield>service_lines</structfield>
198	array (that is the number of lines potentially carrying data).</entry>
199		  </row>
200		  <row>
201		    <entry>__u32</entry>
202		    <entry><structfield>reserved</structfield>[2]</entry>
203		    <entry spanname="hspan">This array is reserved for future
204	extensions. Applications and drivers must set it to zero.</entry>
205		  </row>
206		</tbody>
207	      </tgroup>
208	    </table>
209	
210	    <!-- See also vidioc-g-sliced-vbi-cap.sgml -->
211	    <table frame="none" pgwide="1" id="vbi-services2">
212	      <title>Sliced VBI services</title>
213	      <tgroup cols="5">
214		<colspec colname="c1" colwidth="2*" />
215		<colspec colname="c2" colwidth="1*" />
216		<colspec colname="c3" colwidth="1*" />
217		<colspec colname="c4" colwidth="2*" />
218		<colspec colname="c5" colwidth="2*" />
219		<spanspec namest="c3" nameend="c5" spanname="rlp" />
220		<thead>
221		  <row>
222		    <entry>Symbol</entry>
223		    <entry>Value</entry>
224		    <entry>Reference</entry>
225		    <entry>Lines, usually</entry>
226		    <entry>Payload</entry>
227		  </row>
228		</thead>
229		<tbody valign="top">
230		  <row>
231		    <entry><constant>V4L2_SLICED_TELETEXT_B</constant>
232	(Teletext System B)</entry>
233		    <entry>0x0001</entry>
234		    <entry><xref linkend="ets300706" />, <xref linkend="itu653" /></entry>
235		    <entry>PAL/SECAM line 7-22, 320-335 (second field 7-22)</entry>
236		    <entry>Last 42 of the 45 byte Teletext packet, that is
237	without clock run-in and framing code, lsb first transmitted.</entry>
238		  </row>
239		  <row>
240		    <entry><constant>V4L2_SLICED_VPS</constant></entry>
241		    <entry>0x0400</entry>
242		    <entry><xref linkend="ets300231" /></entry>
243		    <entry>PAL line 16</entry>
244		    <entry>Byte number 3 to 15 according to Figure 9 of
245	ETS&nbsp;300&nbsp;231, lsb first transmitted.</entry>
246		  </row>
247		  <row>
248		    <entry><constant>V4L2_SLICED_CAPTION_525</constant></entry>
249		    <entry>0x1000</entry>
250		    <entry><xref linkend="eia608" /></entry>
251		    <entry>NTSC line 21, 284 (second field 21)</entry>
252		    <entry>Two bytes in transmission order, including parity
253	bit, lsb first transmitted.</entry>
254		  </row>
255		  <row>
256		    <entry><constant>V4L2_SLICED_WSS_625</constant></entry>
257		    <entry>0x4000</entry>
258		    <entry><xref linkend="itu1119" />, <xref linkend="en300294" /></entry>
259		    <entry>PAL/SECAM line 23</entry>
260		    <entry><screen>
261	Byte         0                 1
262	      msb         lsb  msb           lsb
263	 Bit  7 6 5 4 3 2 1 0  x x 13 12 11 10 9
264	</screen></entry>
265		  </row>
266		  <row>
267		    <entry><constant>V4L2_SLICED_VBI_525</constant></entry>
268		    <entry>0x1000</entry>
269		    <entry spanname="rlp">Set of services applicable to 525
270	line systems.</entry>
271		  </row>
272		  <row>
273		    <entry><constant>V4L2_SLICED_VBI_625</constant></entry>
274		    <entry>0x4401</entry>
275		    <entry spanname="rlp">Set of services applicable to 625
276	line systems.</entry>
277		  </row>
278		</tbody>
279	      </tgroup>
280	    </table>
281	
282	    <para>Drivers may return an &EINVAL; when applications attempt to
283	read or write data without prior format negotiation, after switching
284	the video standard (which may invalidate the negotiated VBI
285	parameters) and after switching the video input (which may change the
286	video standard as a side effect). The &VIDIOC-S-FMT; ioctl may return
287	an &EBUSY; when applications attempt to change the format while i/o is
288	in progress (between a &VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; call,
289	and after the first &func-read; or &func-write; call).</para>
290	  </section>
291	
292	  <section>
293	    <title>Reading and writing sliced VBI data</title>
294	
295	    <para>A single &func-read; or &func-write; call must pass all data
296	belonging to one video frame. That is an array of
297	<structname>v4l2_sliced_vbi_data</structname> structures with one or
298	more elements and a total size not exceeding
299	<structfield>io_size</structfield> bytes. Likewise in streaming I/O
300	mode one buffer of <structfield>io_size</structfield> bytes must
301	contain data of one video frame. The <structfield>id</structfield> of
302	unused <structname>v4l2_sliced_vbi_data</structname> elements must be
303	zero.</para>
304	
305	    <table frame="none" pgwide="1" id="v4l2-sliced-vbi-data">
306	      <title>struct
307	<structname>v4l2_sliced_vbi_data</structname></title>
308	      <tgroup cols="3">
309		&cs-def;
310		<tbody valign="top">
311		  <row>
312		    <entry>__u32</entry>
313		    <entry><structfield>id</structfield></entry>
314		    <entry>A flag from <xref linkend="vbi-services" />
315	identifying the type of data in this packet. Only a single bit must be
316	set. When the <structfield>id</structfield> of a captured packet is
317	zero, the packet is empty and the contents of other fields are
318	undefined. Applications shall ignore empty packets. When the
319	<structfield>id</structfield> of a packet for output is zero the
320	contents of the <structfield>data</structfield> field are undefined
321	and the driver must no longer insert data on the requested
322	<structfield>field</structfield> and
323	<structfield>line</structfield>.</entry>
324		  </row>
325		  <row>
326		    <entry>__u32</entry>
327		    <entry><structfield>field</structfield></entry>
328		    <entry>The video field number this data has been captured
329	from, or shall be inserted at. <constant>0</constant> for the first
330	field, <constant>1</constant> for the second field.</entry>
331		  </row>
332		  <row>
333		    <entry>__u32</entry>
334		    <entry><structfield>line</structfield></entry>
335		    <entry>The field (as opposed to frame) line number this
336	data has been captured from, or shall be inserted at. See <xref
337		    linkend="vbi-525" /> and <xref linkend="vbi-625" /> for valid
338	values. Sliced VBI capture devices can set the line number of all
339	packets to <constant>0</constant> if the hardware cannot reliably
340	identify scan lines. The field number must always be valid.</entry>
341		  </row>
342		  <row>
343		    <entry>__u32</entry>
344		    <entry><structfield>reserved</structfield></entry>
345		    <entry>This field is reserved for future extensions.
346	Applications and drivers must set it to zero.</entry>
347		  </row>
348		  <row>
349		    <entry>__u8</entry>
350		    <entry><structfield>data</structfield>[48]</entry>
351		    <entry>The packet payload. See <xref
352		    linkend="vbi-services" /> for the contents and number of
353	bytes passed for each data type. The contents of padding bytes at the
354	end of this array are undefined, drivers and applications shall ignore
355	them.</entry>
356		  </row>
357		</tbody>
358	      </tgroup>
359	    </table>
360	
361	    <para>Packets are always passed in ascending line number order,
362	without duplicate line numbers. The &func-write; function and the
363	&VIDIOC-QBUF; ioctl must return an &EINVAL; when applications violate
364	this rule. They must also return an &EINVAL; when applications pass an
365	incorrect field or line number, or a combination of
366	<structfield>field</structfield>, <structfield>line</structfield> and
367	<structfield>id</structfield> which has not been negotiated with the
368	&VIDIOC-G-FMT; or &VIDIOC-S-FMT; ioctl. When the line numbers are
369	unknown the driver must pass the packets in transmitted order. The
370	driver can insert empty packets with <structfield>id</structfield> set
371	to zero anywhere in the packet array.</para>
372	
373	    <para>To assure synchronization and to distinguish from frame
374	dropping, when a captured frame does not carry any of the requested
375	data services drivers must pass one or more empty packets. When an
376	application fails to pass VBI data in time for output, the driver
377	must output the last VPS and WSS packet again, and disable the output
378	of Closed Caption and Teletext data, or output data which is ignored
379	by Closed Caption and Teletext decoders.</para>
380	
381	    <para>A sliced VBI device may support <link
382	linkend="rw">read/write</link> and/or streaming (<link
383	linkend="mmap">memory mapping</link> and/or <link linkend="userp">user
384	pointer</link>) I/O. The latter bears the possibility of synchronizing
385	video and VBI data by using buffer timestamps.</para>
386	
387	  </section>
388	
389	  <section>
390	    <title>Sliced VBI Data in MPEG Streams</title>
391	
392	    <para>If a device can produce an MPEG output stream, it may be
393	capable of providing <link
394	linkend="sliced-vbi-format-negotitation">negotiated sliced VBI
395	services</link> as data embedded in the MPEG stream.  Users or
396	applications control this sliced VBI data insertion with the <link
397	linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link>
398	control.</para>
399	
400	    <para>If the driver does not provide the <link
401	linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link>
402	control, or only allows that control to be set to <link
403	linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
404	V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link>, then the device
405	cannot embed sliced VBI data in the MPEG stream.</para>
406	
407	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt">
408	V4L2_CID_MPEG_STREAM_VBI_FMT</link> control does not implicitly set
409	the device driver to capture nor cease capturing sliced VBI data.  The
410	control only indicates to embed sliced VBI data in the MPEG stream, if
411	an application has negotiated sliced VBI service be captured.</para>
412	
413	    <para>It may also be the case that a device can embed sliced VBI
414	data in only certain types of MPEG streams: for example in an MPEG-2
415	PS but not an MPEG-2 TS.  In this situation, if sliced VBI data
416	insertion is requested, the sliced VBI data will be embedded in MPEG
417	stream types when supported, and silently omitted from MPEG stream
418	types where sliced VBI data insertion is not supported by the device.
419	</para>
420	
421	    <para>The following subsections specify the format of the
422	embedded sliced VBI data.</para>
423	
424	  <section>
425	    <title>MPEG Stream Embedded, Sliced VBI Data Format: NONE</title>
426	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
427	V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link> embedded sliced VBI
428	format shall be interpreted by drivers as a control to cease
429	embedding sliced VBI data in MPEG streams.  Neither the device nor
430	driver shall insert "empty" embedded sliced VBI data packets in the
431	MPEG stream when this format is set.  No MPEG stream data structures
432	are specified for this format.</para>
433	  </section>
434	
435	  <section>
436	    <title>MPEG Stream Embedded, Sliced VBI Data Format: IVTV</title>
437	    <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant>
438	V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> embedded sliced VBI
439	format, when supported, indicates to the driver to embed up to 36
440	lines of sliced VBI data per frame in an MPEG-2 <emphasis>Private
441	Stream 1 PES</emphasis> packet encapsulated in an MPEG-2 <emphasis>
442	Program Pack</emphasis> in the MPEG stream.</para>
443	
444	    <para><emphasis>Historical context</emphasis>: This format
445	specification originates from a custom, embedded, sliced VBI data
446	format used by the <filename>ivtv</filename> driver.  This format
447	has already been informally specified in the kernel sources in the
448	file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>
449	.  The maximum size of the payload and other aspects of this format
450	are driven by the CX23415 MPEG decoder's capabilities and limitations
451	with respect to extracting, decoding, and displaying sliced VBI data
452	embedded within an MPEG stream.</para>
453	
454	    <para>This format's use is <emphasis>not</emphasis> exclusive to
455	the <filename>ivtv</filename> driver <emphasis>nor</emphasis>
456	exclusive to CX2341x devices, as the sliced VBI data packet insertion
457	into the MPEG stream is implemented in driver software.  At least the
458	<filename>cx18</filename> driver provides sliced VBI data insertion
459	into an MPEG-2 PS in this format as well.</para>
460	
461	    <para>The following definitions specify the payload of the
462	MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packets that contain
463	sliced VBI data when <link linkend="v4l2-mpeg-stream-vbi-fmt">
464	<constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> is set.
465	(The MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packet header
466	and encapsulating MPEG-2 <emphasis>Program Pack</emphasis> header are
467	not detailed here.  Please refer to the MPEG-2 specifications for
468	details on those packet headers.)</para>
469	
470	    <para>The payload of the MPEG-2 <emphasis>Private Stream 1 PES
471	</emphasis> packets that contain sliced VBI data is specified by
472	&v4l2-mpeg-vbi-fmt-ivtv;.  The payload is variable
473	length, depending on the actual number of lines of sliced VBI data
474	present in a video frame.  The payload may be padded at the end with
475	unspecified fill bytes to align the end of the payload to a 4-byte
476	boundary.  The payload shall never exceed 1552 bytes (2 fields with
477	18 lines/field with 43 bytes of data/line and a 4 byte magic number).
478	</para>
479	
480	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv">
481	      <title>struct <structname>v4l2_mpeg_vbi_fmt_ivtv</structname>
482	      </title>
483	      <tgroup cols="4">
484		&cs-ustr;
485		<tbody valign="top">
486		  <row>
487		    <entry>__u8</entry>
488		    <entry><structfield>magic</structfield>[4]</entry>
489		    <entry></entry>
490		    <entry>A "magic" constant from <xref
491		    linkend="v4l2-mpeg-vbi-fmt-ivtv-magic" /> that indicates
492	this is a valid sliced VBI data payload and also indicates which
493	member of the anonymous union, <structfield>itv0</structfield> or
494	<structfield>ITV0</structfield>, to use for the payload data.</entry>
495		  </row>
496		  <row>
497		    <entry>union</entry>
498		    <entry>(anonymous)</entry>
499		  </row>
500		  <row>
501		    <entry></entry>
502		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0">
503		      <structname>v4l2_mpeg_vbi_itv0</structname></link>
504		    </entry>
505		    <entry><structfield>itv0</structfield></entry>
506		    <entry>The primary form of the sliced VBI data payload
507	that contains anywhere from 1 to 35 lines of sliced VBI data.
508	Line masks are provided in this form of the payload indicating
509	which VBI lines are provided.</entry>
510		  </row>
511		  <row>
512		    <entry></entry>
513		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-1">
514		      <structname>v4l2_mpeg_vbi_ITV0</structname></link>
515		    </entry>
516		    <entry><structfield>ITV0</structfield></entry>
517		    <entry>An alternate form of the sliced VBI data payload
518	used when 36 lines of sliced VBI data are present.  No line masks are
519	provided in this form of the payload; all valid line mask bits are
520	implcitly set.</entry>
521		  </row>
522		</tbody>
523	      </tgroup>
524	    </table>
525	
526	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv-magic">
527	      <title>Magic Constants for &v4l2-mpeg-vbi-fmt-ivtv;
528		<structfield>magic</structfield> field</title>
529	      <tgroup cols="3">
530		&cs-def;
531		<thead>
532		  <row>
533		    <entry align="left">Defined Symbol</entry>
534		    <entry align="left">Value</entry>
535		    <entry align="left">Description</entry>
536		  </row>
537		</thead>
538		<tbody valign="top">
539		  <row>
540		    <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC0</constant>
541		    </entry>
542		    <entry>"itv0"</entry>
543		    <entry>Indicates the <structfield>itv0</structfield>
544	member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid.</entry>
545		  </row>
546		  <row>
547		    <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC1</constant>
548		    </entry>
549		    <entry>"ITV0"</entry>
550		    <entry>Indicates the <structfield>ITV0</structfield>
551	member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid and
552	that 36 lines of sliced VBI data are present.</entry>
553		  </row>
554		</tbody>
555	      </tgroup>
556	    </table>
557	
558	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0">
559	      <title>struct <structname>v4l2_mpeg_vbi_itv0</structname>
560	      </title>
561	      <tgroup cols="3">
562		&cs-str;
563		<tbody valign="top">
564		  <row>
565		    <entry>__le32</entry>
566		    <entry><structfield>linemask</structfield>[2]</entry>
567		    <entry><para>Bitmasks indicating the VBI service lines
568	present.  These <structfield>linemask</structfield> values are stored
569	in little endian byte order in the MPEG stream.  Some reference
570	<structfield>linemask</structfield> bit positions with their
571	corresponding VBI line number and video field are given below.
572	b<subscript>0</subscript> indicates the least significant bit of a
573	<structfield>linemask</structfield> value:<screen>
574	<structfield>linemask</structfield>[0] b<subscript>0</subscript>:		line  6		first field
575	<structfield>linemask</structfield>[0] b<subscript>17</subscript>:		line 23		first field
576	<structfield>linemask</structfield>[0] b<subscript>18</subscript>:		line  6		second field
577	<structfield>linemask</structfield>[0] b<subscript>31</subscript>:		line 19		second field
578	<structfield>linemask</structfield>[1] b<subscript>0</subscript>:		line 20		second field
579	<structfield>linemask</structfield>[1] b<subscript>3</subscript>:		line 23		second field
580	<structfield>linemask</structfield>[1] b<subscript>4</subscript>-b<subscript>31</subscript>:	unused and set to 0</screen></para></entry>
581		  </row>
582		  <row>
583		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line">
584		      <structname>v4l2_mpeg_vbi_itv0_line</structname></link>
585		    </entry>
586		    <entry><structfield>line</structfield>[35]</entry>
587		    <entry>This is a variable length array that holds from 1
588	to 35 lines of sliced VBI data.  The sliced VBI data lines present
589	correspond to the bits set in the <structfield>linemask</structfield>
590	array, starting from b<subscript>0</subscript> of <structfield>
591	linemask</structfield>[0] up through b<subscript>31</subscript> of
592	<structfield>linemask</structfield>[0], and from b<subscript>0
593	</subscript> of <structfield>linemask</structfield>[1] up through b
594	<subscript>3</subscript> of <structfield>linemask</structfield>[1].
595	<structfield>line</structfield>[0] corresponds to the first bit
596	found set in the <structfield>linemask</structfield> array,
597	<structfield>line</structfield>[1] corresponds to the second bit
598	found set in the <structfield>linemask</structfield> array, etc.
599	If no <structfield>linemask</structfield> array bits are set, then
600	<structfield>line</structfield>[0] may contain one line of
601	unspecified data that should be ignored by applications.</entry>
602		  </row>
603		</tbody>
604	      </tgroup>
605	    </table>
606	
607	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-1">
608	      <title>struct <structname>v4l2_mpeg_vbi_ITV0</structname>
609	      </title>
610	      <tgroup cols="3">
611		&cs-str;
612		<tbody valign="top">
613		  <row>
614		    <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line">
615		      <structname>v4l2_mpeg_vbi_itv0_line</structname></link>
616		    </entry>
617		    <entry><structfield>line</structfield>[36]</entry>
618		    <entry>A fixed length array of 36 lines of sliced VBI
619	data.  <structfield>line</structfield>[0] through <structfield>line
620	</structfield>[17] correspond to lines 6 through 23 of the
621	first field.  <structfield>line</structfield>[18] through
622	<structfield>line</structfield>[35] corresponds to lines 6
623	through 23 of the second field.</entry>
624		  </row>
625		</tbody>
626	      </tgroup>
627	    </table>
628	
629	    <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-line">
630	      <title>struct <structname>v4l2_mpeg_vbi_itv0_line</structname>
631	      </title>
632	      <tgroup cols="3">
633		&cs-str;
634		<tbody valign="top">
635		  <row>
636		    <entry>__u8</entry>
637		    <entry><structfield>id</structfield></entry>
638		    <entry>A line identifier value from
639	<xref linkend="ITV0-Line-Identifier-Constants" /> that indicates
640	the type of sliced VBI data stored on this line.</entry>
641		  </row>
642		  <row>
643		    <entry>__u8</entry>
644		    <entry><structfield>data</structfield>[42]</entry>
645		    <entry>The sliced VBI data for the line.</entry>
646		  </row>
647		</tbody>
648	      </tgroup>
649	    </table>
650	
651	    <table frame="none" pgwide="1" id="ITV0-Line-Identifier-Constants">
652	      <title>Line Identifiers for struct <link
653	      linkend="v4l2-mpeg-vbi-itv0-line"><structname>
654	v4l2_mpeg_vbi_itv0_line</structname></link> <structfield>id
655	</structfield> field</title>
656	      <tgroup cols="3">
657		&cs-def;
658		<thead>
659		  <row>
660		    <entry align="left">Defined Symbol</entry>
661		    <entry align="left">Value</entry>
662		    <entry align="left">Description</entry>
663		  </row>
664		</thead>
665		<tbody valign="top">
666		  <row>
667		    <entry><constant>V4L2_MPEG_VBI_IVTV_TELETEXT_B</constant>
668		    </entry>
669		    <entry>1</entry>
670		    <entry>Refer to <link linkend="vbi-services2">
671	Sliced VBI services</link> for a description of the line payload.</entry>
672		  </row>
673		  <row>
674		    <entry><constant>V4L2_MPEG_VBI_IVTV_CAPTION_525</constant>
675		    </entry>
676		    <entry>4</entry>
677		    <entry>Refer to <link linkend="vbi-services2">
678	Sliced VBI services</link> for a description of the line payload.</entry>
679		  </row>
680		  <row>
681		    <entry><constant>V4L2_MPEG_VBI_IVTV_WSS_625</constant>
682		    </entry>
683		    <entry>5</entry>
684		    <entry>Refer to <link linkend="vbi-services2">
685	Sliced VBI services</link> for a description of the line payload.</entry>
686		  </row>
687		  <row>
688		    <entry><constant>V4L2_MPEG_VBI_IVTV_VPS</constant>
689		    </entry>
690		    <entry>7</entry>
691		    <entry>Refer to <link linkend="vbi-services2">
692	Sliced VBI services</link> for a description of the line payload.</entry>
693		  </row>
694		</tbody>
695	      </tgroup>
696	    </table>
697	
698	  </section>
699	  </section>
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