media/v4l/dev-raw-vbi.xml

3   <para>VBI is an abbreviation of Vertical Blanking Interval, a gap
5 no picture information is transmitted, allowing some time while the
9 modulated<footnote><para>ASK: Amplitude-Shift Keying. A high signal
14   <para>Subject of this interface type is raw VBI data, as sampled off
16 The data format is similar to uncompressed video images, a number of
23 <filename>/dev/vbi</filename> is typically a symbolic link to the
28 devices VBI capturing and output is also available as device function
30 data with these devices applications must call the &VIDIOC-S-FMT;
32 or output is the default device function.</para>
40 <structfield>capabilities</structfield> field of &v4l2-capability;
41 returned by the &VIDIOC-QUERYCAP; ioctl. At least one of the
66 reset at &func-open; time to permit Unix tool chains, programming a
74 &v4l2-format; to <constant>V4L2_BUF_TYPE_VBI_CAPTURE</constant> or
76 &VIDIOC-G-FMT; ioctl with a pointer to this structure. Drivers fill
77 the &v4l2-vbi-format; <structfield>vbi</structfield> member of the
81 <structfield>type</structfield> field of a &v4l2-format; as above and
82 initialize all fields of the &v4l2-vbi-format;
86 &VIDIOC-S-FMT; ioctl with a pointer to this structure. Drivers return
96 return <errorcode>EBUSY</errorcode>, at the &VIDIOC-STREAMON; ioctl
104 <constant>VIDIOC_TRY_FMT</constant> is optional.</para>
106       <table pgwide="1" frame="none" id="v4l2-vbi-format">
109 	  &cs-str;
124 edge. See also <xref linkend="vbi-hsync" />.</para></entry>
135 linkend="pixfmt" />, a four-character-code.<footnote>
139 		  </footnote> Usually this is
143 For example, the MSB does not necessarily indicate if the signal is
150 	      <entry>This is the scanning system line number
152 second field respectively. See <xref linkend="vbi-525" /> and
153 <xref linkend="vbi-625" /> for valid values. VBI input drivers can
170 <structfield>count</structfield> value to zero if no data is required
172 scanning system is progressive, &ie; not interlaced. The
175 return both count values non-zero.</para><para>Both
177 outside the bounds depicted in <xref linkend="vbi-525" /> and <xref
178 		    linkend="vbi-625" />, or a field image covering
182 determine the current video standard selection. The &v4l2-std-id; or
183 the <structfield>framelines</structfield> field of &v4l2-standard; can
189 	      <entry>See <xref linkend="vbifmt-flags" /> below. Currently
196 	      <entry>This array is reserved for future extensions.
203       <table pgwide="1" frame="none" id="vbifmt-flags">
206 	  &cs-def;
215 is set the first or second field may be stored first, however the
220 cannot be reliable decoded or encoded when
221 <constant>V4L2_VBI_UNSYNC</constant> is set.</para>
229 the second field (compare <xref linkend="field-order" />
232 field is first in memory depends on the video standard). When this
233 flag is set, the two fields are interlaced (cf.
238 images and is unable to separate the fields for VBI capturing at
240 <structfield>count</structfield> values are equal and non-zero.</entry>
246       <figure id="vbi-hsync">
261       <figure id="vbi-525">
262 	<title>ITU-R 525 line numbering (M/NTSC and M/PAL)</title>
275 starts in line 264 and not 263.5 because half line capturing is not
281       <figure id="vbi-625">
282 	<title>ITU-R 625 line numbering</title>
295 starts in line 314 and not 313.5 because half line capturing is not
306 driver. A format change during active I/O is not permitted.</para>
313 implementation, the smallest unit of data passed at a time is one
323       <para>The sample size is most likely always one byte,
334       <para>Remember the &VIDIOC-STREAMON; ioctl and the first read(),
337 unavailable, for example the device is already in use by another