media/v4l/dev-raw-vbi.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
4 .. _raw-vbi:
12 information is transmitted, allowing some time while the electron beam
64 time to permit Unix tool chains, programming a device and then reading
89 overlap, or when the driver supports multiple opens and another process
106 .. flat-table:: struct v4l2_vbi_format
107     :header-rows:  0
108     :stub-columns: 0
111     * - __u32
112       - ``sampling_rate``
113       - Samples per second, i. e. unit 1 Hz.
114     * - __u32
115       - ``offset``
116       - Horizontal offset of the VBI image, relative to the leading edge
120 	:ref:`vbi-hsync`.
121     * - __u32
122       - ``samples_per_line``
123       -
124     * - __u32
125       - ``sample_format``
126       - Defines the sample format as in :ref:`pixfmt`, a
127 	four-character-code. [#f2]_ Usually this is ``V4L2_PIX_FMT_GREY``,
134     * - __u32
135       - ``start``\ [#f2]_
136       - This is the scanning system line number associated with the first
138 	respectively. See :ref:`vbi-525` and :ref:`vbi-625` for valid
147     * - __u32
148       - ``count``\ [#f2]_
149       - The number of lines in the first and second field image,
151     * - :cspan:`2`
163 	return both count values non-zero.
171 	:ref:`v4l2_std_id <v4l2-std-id>` or the ``framelines`` field
174     * - __u32
175       - ``flags``
176       - See :ref:`vbifmt-flags` below. Currently only drivers set flags,
178     * - __u32
179       - ``reserved``\ [#f2]_
180       - This array is reserved for future extensions. Drivers and
185 .. _vbifmt-flags:
187 .. flat-table:: Raw VBI Format Flags
188     :header-rows:  0
189     :stub-columns: 0
192     * - ``V4L2_VBI_UNSYNC``
193       - 0x0001
194       - This flag indicates hardware which does not properly distinguish
201     * - ``V4L2_VBI_INTERLACED``
202       - 0x0002
203       - By default the two field images will be passed sequentially; all
205 	(compare :ref:`field-order` ``V4L2_FIELD_SEQ_TB`` and
213 	fields for VBI capturing at the same time. For simplicity setting
215 	non-zero.
218 .. _vbi-hsync:
220 .. kernel-figure:: vbi_hsync.svg
226 .. _vbi-525:
228 .. kernel-figure:: vbi_525.svg
232     **Figure 4.2. ITU-R 525 line numbering (M/NTSC and M/PAL)**
234 .. _vbi-625:
236 .. kernel-figure:: vbi_625.svg
240     **Figure 4.3. ITU-R 625 line numbering**
253 implementation, the smallest unit of data passed at a time is one frame,
258 .. code-block:: c
279    ASK: Amplitude-Shift Keying. A high signal level represents a '1'
292    The valid values ar shown at :ref:`vbi-525` and :ref:`vbi-625`.