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.. -*- coding: utf-8; mode: rst -*-
.. _VIDIOC_G_SLICED_VBI_CAP:
*****************************
ioctl VIDIOC_G_SLICED_VBI_CAP
*****************************
Name
====
VIDIOC_G_SLICED_VBI_CAP - Query sliced VBI capabilities
Synopsis
========
.. c:function:: int ioctl( int fd, VIDIOC_G_SLICED_VBI_CAP, struct v4l2_sliced_vbi_cap *argp )
:name: VIDIOC_G_SLICED_VBI_CAP
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``argp``
Description
===========
To find out which data services are supported by a sliced VBI capture or
output device, applications initialize the ``type`` field of a struct
:c:type:`v4l2_sliced_vbi_cap`, clear the
``reserved`` array and call the :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl. The
driver fills in the remaining fields or returns an ``EINVAL`` error code if
the sliced VBI API is unsupported or ``type`` is invalid.
.. note::
The ``type`` field was added, and the ioctl changed from read-only
to write-read, in Linux 2.6.19.
.. c:type:: v4l2_sliced_vbi_cap
.. tabularcolumns:: |p{1.2cm}|p{4.2cm}|p{4.1cm}|p{4.0cm}|p{4.0cm}|
.. flat-table:: struct v4l2_sliced_vbi_cap
:header-rows: 0
:stub-columns: 0
:widths: 3 3 2 2 2
* - __u16
- ``service_set``
- :cspan:`2` A set of all data services supported by the driver.
Equal to the union of all elements of the ``service_lines`` array.
* - __u16
- ``service_lines``\ [2][24]
- :cspan:`2` Each element of this array contains a set of data
services the hardware can look for or insert into a particular
scan line. Data services are defined in :ref:`vbi-services`.
Array indices map to ITU-R line numbers\ [#f1]_ as follows:
* -
-
- Element
- 525 line systems
- 625 line systems
* -
-
- ``service_lines``\ [0][1]
- 1
- 1
* -
-
- ``service_lines``\ [0][23]
- 23
- 23
* -
-
- ``service_lines``\ [1][1]
- 264
- 314
* -
-
- ``service_lines``\ [1][23]
- 286
- 336
* -
* -
-
- :cspan:`2` The number of VBI lines the hardware can capture or
output per frame, or the number of services it can identify on a
given line may be limited. For example on PAL line 16 the hardware
may be able to look for a VPS or Teletext signal, but not both at
the same time. Applications can learn about these limits using the
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl as described in
:ref:`sliced`.
* -
* -
-
- :cspan:`2` Drivers must set ``service_lines`` [0][0] and
``service_lines``\ [1][0] to zero.
* - __u32
- ``type``
- Type of the data stream, see :c:type:`v4l2_buf_type`. Should be
``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` or
``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``.
* - __u32
- ``reserved``\ [3]
- :cspan:`2` This array is reserved for future extensions.
Applications and drivers must set it to zero.
.. [#f1]
See also :ref:`vbi-525` and :ref:`vbi-625`.
.. raw:: latex
\begin{adjustbox}{width=\columnwidth}
.. tabularcolumns:: |p{5.0cm}|p{1.4cm}|p{3.0cm}|p{2.5cm}|p{9.0cm}|
.. _vbi-services:
.. flat-table:: Sliced VBI services
:header-rows: 1
:stub-columns: 0
:widths: 2 1 1 2 2
* - Symbol
- Value
- Reference
- Lines, usually
- Payload
* - ``V4L2_SLICED_TELETEXT_B`` (Teletext System B)
- 0x0001
- :ref:`ets300706`,
:ref:`itu653`
- PAL/SECAM line 7-22, 320-335 (second field 7-22)
- Last 42 of the 45 byte Teletext packet, that is without clock
run-in and framing code, lsb first transmitted.
* - ``V4L2_SLICED_VPS``
- 0x0400
- :ref:`ets300231`
- PAL line 16
- Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb
first transmitted.
* - ``V4L2_SLICED_CAPTION_525``
- 0x1000
- :ref:`cea608`
- NTSC line 21, 284 (second field 21)
- Two bytes in transmission order, including parity bit, lsb first
transmitted.
* - ``V4L2_SLICED_WSS_625``
- 0x4000
- :ref:`en300294`,
:ref:`itu1119`
- PAL/SECAM line 23
-
::
Byte 0 1
msb lsb msb lsb
Bit 7 6 5 4 3 2 1 0 x x 13 12 11 10 9
* - ``V4L2_SLICED_VBI_525``
- 0x1000
- :cspan:`2` Set of services applicable to 525 line systems.
* - ``V4L2_SLICED_VBI_625``
- 0x4401
- :cspan:`2` Set of services applicable to 625 line systems.
.. raw:: latex
\end{adjustbox}\newline\newline
Return Value
============
On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
EINVAL
The value in the ``type`` field is wrong.
|
