path: root/Documentation/userspace-api/media/v4l/vidioc-g-sliced-vbi-cap.rst

.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/userspace-api/media/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _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``
    Pointer to struct :c:type:`v4l2_sliced_vbi_cap`.


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

    \scriptsize

.. tabularcolumns:: |p{3.5cm}|p{1.0cm}|p{2.0cm}|p{2.0cm}|p{8.0cm}|

.. _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

    \normalsize


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.