196 lines
4.8 KiB
ReStructuredText
196 lines
4.8 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_G_SLICED_VBI_CAP:
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*****************************
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ioctl VIDIOC_G_SLICED_VBI_CAP
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*****************************
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Name
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====
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VIDIOC_G_SLICED_VBI_CAP - Query sliced VBI capabilities
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_G_SLICED_VBI_CAP, struct v4l2_sliced_vbi_cap *argp )
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:name: VIDIOC_G_SLICED_VBI_CAP
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``argp``
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Pointer to struct :c:type:`v4l2_sliced_vbi_cap`.
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Description
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===========
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To find out which data services are supported by a sliced VBI capture or
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output device, applications initialize the ``type`` field of a struct
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:c:type:`v4l2_sliced_vbi_cap`, clear the
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``reserved`` array and call the :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl. The
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driver fills in the remaining fields or returns an ``EINVAL`` error code if
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the sliced VBI API is unsupported or ``type`` is invalid.
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.. note::
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The ``type`` field was added, and the ioctl changed from read-only
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to write-read, in Linux 2.6.19.
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.. c:type:: v4l2_sliced_vbi_cap
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.. tabularcolumns:: |p{1.2cm}|p{4.2cm}|p{4.1cm}|p{4.0cm}|p{4.0cm}|
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.. flat-table:: struct v4l2_sliced_vbi_cap
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:header-rows: 0
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:stub-columns: 0
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:widths: 3 3 2 2 2
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* - __u16
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- ``service_set``
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- :cspan:`2` A set of all data services supported by the driver.
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Equal to the union of all elements of the ``service_lines`` array.
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* - __u16
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- ``service_lines``\ [2][24]
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- :cspan:`2` Each element of this array contains a set of data
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services the hardware can look for or insert into a particular
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scan line. Data services are defined in :ref:`vbi-services`.
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Array indices map to ITU-R line numbers\ [#f1]_ as follows:
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* -
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-
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- Element
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- 525 line systems
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- 625 line systems
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* -
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-
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- ``service_lines``\ [0][1]
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- 1
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- 1
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* -
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-
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- ``service_lines``\ [0][23]
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- 23
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- 23
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* -
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-
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- ``service_lines``\ [1][1]
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- 264
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- 314
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* -
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-
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- ``service_lines``\ [1][23]
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- 286
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- 336
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* -
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* -
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-
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- :cspan:`2` The number of VBI lines the hardware can capture or
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output per frame, or the number of services it can identify on a
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given line may be limited. For example on PAL line 16 the hardware
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may be able to look for a VPS or Teletext signal, but not both at
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the same time. Applications can learn about these limits using the
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:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl as described in
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:ref:`sliced`.
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* -
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* -
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-
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- :cspan:`2` Drivers must set ``service_lines`` [0][0] and
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``service_lines``\ [1][0] to zero.
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* - __u32
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- ``type``
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- Type of the data stream, see :c:type:`v4l2_buf_type`. Should be
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``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` or
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``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``.
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* - __u32
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- ``reserved``\ [3]
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- :cspan:`2` This array is reserved for future extensions.
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Applications and drivers must set it to zero.
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.. [#f1]
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See also :ref:`vbi-525` and :ref:`vbi-625`.
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.. raw:: latex
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\scriptsize
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.. tabularcolumns:: |p{3.5cm}|p{1.0cm}|p{2.0cm}|p{2.0cm}|p{8.0cm}|
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.. _vbi-services:
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.. flat-table:: Sliced VBI services
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:header-rows: 1
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:stub-columns: 0
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:widths: 2 1 1 2 2
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* - Symbol
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- Value
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- Reference
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- Lines, usually
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- Payload
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* - ``V4L2_SLICED_TELETEXT_B`` (Teletext System B)
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- 0x0001
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- :ref:`ets300706`,
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:ref:`itu653`
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- PAL/SECAM line 7-22, 320-335 (second field 7-22)
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- Last 42 of the 45 byte Teletext packet, that is without clock
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run-in and framing code, lsb first transmitted.
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* - ``V4L2_SLICED_VPS``
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- 0x0400
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- :ref:`ets300231`
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- PAL line 16
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- Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb
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first transmitted.
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* - ``V4L2_SLICED_CAPTION_525``
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- 0x1000
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- :ref:`cea608`
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- NTSC line 21, 284 (second field 21)
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- Two bytes in transmission order, including parity bit, lsb first
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transmitted.
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* - ``V4L2_SLICED_WSS_625``
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- 0x4000
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- :ref:`en300294`,
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:ref:`itu1119`
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- PAL/SECAM line 23
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-
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::
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Byte 0 1
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msb lsb msb lsb
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Bit 7 6 5 4 3 2 1 0 x x 13 12 11 10 9
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* - ``V4L2_SLICED_VBI_525``
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- 0x1000
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- :cspan:`2` Set of services applicable to 525 line systems.
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* - ``V4L2_SLICED_VBI_625``
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- 0x4401
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- :cspan:`2` Set of services applicable to 625 line systems.
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.. raw:: latex
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\normalsize
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The value in the ``type`` field is wrong.
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