89 lines
3.3 KiB
ReStructuredText
89 lines
3.3 KiB
ReStructuredText
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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. _fm-rx-controls:
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*****************************
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FM Receiver Control Reference
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*****************************
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The FM Receiver (FM_RX) class includes controls for common features of
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FM Reception capable devices.
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.. _fm-rx-control-id:
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FM_RX Control IDs
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=================
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``V4L2_CID_FM_RX_CLASS (class)``
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The FM_RX class descriptor. Calling
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:ref:`VIDIOC_QUERYCTRL` for this control will
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return a description of this control class.
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``V4L2_CID_RDS_RECEPTION (boolean)``
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Enables/disables RDS reception by the radio tuner
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``V4L2_CID_RDS_RX_PTY (integer)``
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Gets RDS Programme Type field. This encodes up to 31 pre-defined
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programme types.
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``V4L2_CID_RDS_RX_PS_NAME (string)``
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Gets the Programme Service name (PS_NAME). It is intended for
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static display on a receiver. It is the primary aid to listeners in
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programme service identification and selection. In Annex E of
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:ref:`iec62106`, the RDS specification, there is a full
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description of the correct character encoding for Programme Service
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name strings. Also from RDS specification, PS is usually a single
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eight character text. However, it is also possible to find receivers
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which can scroll strings sized as 8 x N characters. So, this control
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must be configured with steps of 8 characters. The result is it must
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always contain a string with size multiple of 8.
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``V4L2_CID_RDS_RX_RADIO_TEXT (string)``
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Gets the Radio Text info. It is a textual description of what is
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being broadcasted. RDS Radio Text can be applied when broadcaster
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wishes to transmit longer PS names, programme-related information or
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any other text. In these cases, RadioText can be used in addition to
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``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is
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also fully described in Annex E of :ref:`iec62106`. The length of
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Radio Text strings depends on which RDS Block is being used to
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transmit it, either 32 (2A block) or 64 (2B block). However, it is
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also possible to find receivers which can scroll strings sized as 32
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x N or 64 x N characters. So, this control must be configured with
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steps of 32 or 64 characters. The result is it must always contain a
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string with size multiple of 32 or 64.
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``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
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If set, then a traffic announcement is in progress.
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``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
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If set, then the tuned programme carries traffic announcements.
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``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)``
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If set, then this channel broadcasts music. If cleared, then it
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broadcasts speech. If the transmitter doesn't make this distinction,
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then it will be set.
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``V4L2_CID_TUNE_DEEMPHASIS``
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(enum)
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enum v4l2_deemphasis -
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Configures the de-emphasis value for reception. A de-emphasis filter
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is applied to the broadcast to accentuate the high audio
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frequencies. Depending on the region, a time constant of either 50
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or 75 useconds is used. The enum v4l2_deemphasis defines possible
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values for de-emphasis. Here they are:
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.. flat-table::
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:header-rows: 0
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:stub-columns: 0
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* - ``V4L2_DEEMPHASIS_DISABLED``
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- No de-emphasis is applied.
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* - ``V4L2_DEEMPHASIS_50_uS``
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- A de-emphasis of 50 uS is used.
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* - ``V4L2_DEEMPHASIS_75_uS``
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- A de-emphasis of 75 uS is used.
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