0001 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
0002
0003 .. _fm-rx-controls:
0004
0005 *****************************
0006 FM Receiver Control Reference
0007 *****************************
0008
0009 The FM Receiver (FM_RX) class includes controls for common features of
0010 FM Reception capable devices.
0011
0012
0013 .. _fm-rx-control-id:
0014
0015 FM_RX Control IDs
0016 =================
0017
0018 ``V4L2_CID_FM_RX_CLASS (class)``
0019 The FM_RX class descriptor. Calling
0020 :ref:`VIDIOC_QUERYCTRL` for this control will
0021 return a description of this control class.
0022
0023 ``V4L2_CID_RDS_RECEPTION (boolean)``
0024 Enables/disables RDS reception by the radio tuner
0025
0026 ``V4L2_CID_RDS_RX_PTY (integer)``
0027 Gets RDS Programme Type field. This encodes up to 31 pre-defined
0028 programme types.
0029
0030 ``V4L2_CID_RDS_RX_PS_NAME (string)``
0031 Gets the Programme Service name (PS_NAME). It is intended for
0032 static display on a receiver. It is the primary aid to listeners in
0033 programme service identification and selection. In Annex E of
0034 :ref:`iec62106`, the RDS specification, there is a full
0035 description of the correct character encoding for Programme Service
0036 name strings. Also from RDS specification, PS is usually a single
0037 eight character text. However, it is also possible to find receivers
0038 which can scroll strings sized as 8 x N characters. So, this control
0039 must be configured with steps of 8 characters. The result is it must
0040 always contain a string with size multiple of 8.
0041
0042 ``V4L2_CID_RDS_RX_RADIO_TEXT (string)``
0043 Gets the Radio Text info. It is a textual description of what is
0044 being broadcasted. RDS Radio Text can be applied when broadcaster
0045 wishes to transmit longer PS names, programme-related information or
0046 any other text. In these cases, RadioText can be used in addition to
0047 ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is
0048 also fully described in Annex E of :ref:`iec62106`. The length of
0049 Radio Text strings depends on which RDS Block is being used to
0050 transmit it, either 32 (2A block) or 64 (2B block). However, it is
0051 also possible to find receivers which can scroll strings sized as 32
0052 x N or 64 x N characters. So, this control must be configured with
0053 steps of 32 or 64 characters. The result is it must always contain a
0054 string with size multiple of 32 or 64.
0055
0056 ``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
0057 If set, then a traffic announcement is in progress.
0058
0059 ``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
0060 If set, then the tuned programme carries traffic announcements.
0061
0062 ``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)``
0063 If set, then this channel broadcasts music. If cleared, then it
0064 broadcasts speech. If the transmitter doesn't make this distinction,
0065 then it will be set.
0066
0067 ``V4L2_CID_TUNE_DEEMPHASIS``
0068 (enum)
0069
0070 enum v4l2_deemphasis -
0071 Configures the de-emphasis value for reception. A de-emphasis filter
0072 is applied to the broadcast to accentuate the high audio
0073 frequencies. Depending on the region, a time constant of either 50
0074 or 75 useconds is used. The enum v4l2_deemphasis defines possible
0075 values for de-emphasis. Here they are:
0076
0077
0078
0079 .. flat-table::
0080 :header-rows: 0
0081 :stub-columns: 0
0082
0083 * - ``V4L2_DEEMPHASIS_DISABLED``
0084 - No de-emphasis is applied.
0085 * - ``V4L2_DEEMPHASIS_50_uS``
0086 - A de-emphasis of 50 uS is used.
0087 * - ``V4L2_DEEMPHASIS_75_uS``
0088 - A de-emphasis of 75 uS is used.
