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There are lots of internal references in the form:
:ref:`foo <foo>`
Simplify them to be just: :ref:`foo`.
Patch generated via this small script:
for j in $(find . -name '*'); do echo $j; perl -ne 'if (m/\`(\S+)\s*\<(\S+)\>\`/) { if (!($1=~'http') && $1 eq $2) { s,\s*\<(\S+)\>,,; } } print $_' <$j >a && mv a $j; done
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
267 lines
5.9 KiB
ReStructuredText
267 lines
5.9 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _rds:
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*************
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RDS Interface
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*************
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The Radio Data System transmits supplementary information in binary
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format, for example the station name or travel information, on an
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inaudible audio subcarrier of a radio program. This interface is aimed
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at devices capable of receiving and/or transmitting RDS information.
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For more information see the core RDS standard :ref:`iec62106` and the
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RBDS standard :ref:`nrsc4`.
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Note that the RBDS standard as is used in the USA is almost identical to
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the RDS standard. Any RDS decoder/encoder can also handle RBDS. Only
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some of the fields have slightly different meanings. See the RBDS
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standard for more information.
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The RBDS standard also specifies support for MMBS (Modified Mobile
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Search). This is a proprietary format which seems to be discontinued.
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The RDS interface does not support this format. Should support for MMBS
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(or the so-called 'E blocks' in general) be needed, then please contact
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the linux-media mailing list:
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`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__.
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Querying Capabilities
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=====================
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Devices supporting the RDS capturing API set the
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``V4L2_CAP_RDS_CAPTURE`` flag in the ``capabilities`` field of struct
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:ref:`v4l2_capability <v4l2-capability>` returned by the
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:ref:`VIDIOC_QUERYCAP` ioctl. Any tuner that
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supports RDS will set the ``V4L2_TUNER_CAP_RDS`` flag in the
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``capability`` field of struct :ref:`v4l2_tuner <v4l2-tuner>`. If the
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driver only passes RDS blocks without interpreting the data the
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``V4L2_TUNER_CAP_RDS_BLOCK_IO`` flag has to be set, see
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:ref:`Reading RDS data <reading-rds-data>`. For future use the flag
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``V4L2_TUNER_CAP_RDS_CONTROLS`` has also been defined. However, a driver
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for a radio tuner with this capability does not yet exist, so if you are
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planning to write such a driver you should discuss this on the
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linux-media mailing list:
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`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__.
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Whether an RDS signal is present can be detected by looking at the
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``rxsubchans`` field of struct :ref:`v4l2_tuner <v4l2-tuner>`: the
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``V4L2_TUNER_SUB_RDS`` will be set if RDS data was detected.
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Devices supporting the RDS output API set the ``V4L2_CAP_RDS_OUTPUT``
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flag in the ``capabilities`` field of struct
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:ref:`v4l2_capability <v4l2-capability>` returned by the
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:ref:`VIDIOC_QUERYCAP` ioctl. Any modulator that
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supports RDS will set the ``V4L2_TUNER_CAP_RDS`` flag in the
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``capability`` field of struct
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:ref:`v4l2_modulator <v4l2-modulator>`. In order to enable the RDS
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transmission one must set the ``V4L2_TUNER_SUB_RDS`` bit in the
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``txsubchans`` field of struct
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:ref:`v4l2_modulator <v4l2-modulator>`. If the driver only passes RDS
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blocks without interpreting the data the ``V4L2_TUNER_CAP_RDS_BLOCK_IO``
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flag has to be set. If the tuner is capable of handling RDS entities
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like program identification codes and radio text, the flag
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``V4L2_TUNER_CAP_RDS_CONTROLS`` should be set, see
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:ref:`Writing RDS data <writing-rds-data>` and
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:ref:`FM Transmitter Control Reference <fm-tx-controls>`.
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.. _reading-rds-data:
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Reading RDS data
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================
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RDS data can be read from the radio device with the
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:ref:`read() <func-read>` function. The data is packed in groups of
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three bytes.
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.. _writing-rds-data:
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Writing RDS data
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================
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RDS data can be written to the radio device with the
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:ref:`write() <func-write>` function. The data is packed in groups of
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three bytes, as follows:
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RDS datastructures
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==================
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.. _v4l2-rds-data:
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.. flat-table:: struct v4l2_rds_data
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 5
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- .. row 1
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- __u8
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- ``lsb``
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- Least Significant Byte of RDS Block
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- .. row 2
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- __u8
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- ``msb``
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- Most Significant Byte of RDS Block
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- .. row 3
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- __u8
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- ``block``
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- Block description
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.. _v4l2-rds-block:
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.. flat-table:: Block description
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 5
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- .. row 1
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- Bits 0-2
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- Block (aka offset) of the received data.
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- .. row 2
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- Bits 3-5
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- Deprecated. Currently identical to bits 0-2. Do not use these
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bits.
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- .. row 3
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- Bit 6
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- Corrected bit. Indicates that an error was corrected for this data
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block.
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- .. row 4
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- Bit 7
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- Error bit. Indicates that an uncorrectable error occurred during
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reception of this block.
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.. _v4l2-rds-block-codes:
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.. flat-table:: Block defines
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 1 5
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- .. row 1
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- V4L2_RDS_BLOCK_MSK
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-
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- 7
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- Mask for bits 0-2 to get the block ID.
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- .. row 2
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- V4L2_RDS_BLOCK_A
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-
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- 0
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- Block A.
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- .. row 3
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- V4L2_RDS_BLOCK_B
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-
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- 1
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- Block B.
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- .. row 4
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- V4L2_RDS_BLOCK_C
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-
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- 2
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- Block C.
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- .. row 5
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- V4L2_RDS_BLOCK_D
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-
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- 3
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- Block D.
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- .. row 6
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- V4L2_RDS_BLOCK_C_ALT
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-
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- 4
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- Block C'.
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- .. row 7
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- V4L2_RDS_BLOCK_INVALID
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- read-only
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- 7
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- An invalid block.
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- .. row 8
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- V4L2_RDS_BLOCK_CORRECTED
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- read-only
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- 0x40
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- A bit error was detected but corrected.
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- .. row 9
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- V4L2_RDS_BLOCK_ERROR
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- read-only
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- 0x80
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- An uncorrectable error occurred.
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.. ------------------------------------------------------------------------------
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.. This file was automatically converted from DocBook-XML with the dbxml
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.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
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.. from the linux kernel, refer to:
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..
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.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
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.. ------------------------------------------------------------------------------
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