1.. Permission is granted to copy, distribute and/or modify this
2.. document under the terms of the GNU Free Documentation License,
3.. Version 1.1 or any later version published by the Free Software
4.. Foundation, with no Invariant Sections, no Front-Cover Texts
5.. and no Back-Cover Texts. A copy of the license is included at
6.. Documentation/userspace-api/media/fdl-appendix.rst.
7..
8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
9
10.. _fm-rx-controls:
11
12*****************************
13FM Receiver Control Reference
14*****************************
15
16The FM Receiver (FM_RX) class includes controls for common features of
17FM Reception capable devices.
18
19
20.. _fm-rx-control-id:
21
22FM_RX Control IDs
23=================
24
25``V4L2_CID_FM_RX_CLASS (class)``
26    The FM_RX class descriptor. Calling
27    :ref:`VIDIOC_QUERYCTRL` for this control will
28    return a description of this control class.
29
30``V4L2_CID_RDS_RECEPTION (boolean)``
31    Enables/disables RDS reception by the radio tuner
32
33``V4L2_CID_RDS_RX_PTY (integer)``
34    Gets RDS Programme Type field. This encodes up to 31 pre-defined
35    programme types.
36
37``V4L2_CID_RDS_RX_PS_NAME (string)``
38    Gets the Programme Service name (PS_NAME). It is intended for
39    static display on a receiver. It is the primary aid to listeners in
40    programme service identification and selection. In Annex E of
41    :ref:`iec62106`, the RDS specification, there is a full
42    description of the correct character encoding for Programme Service
43    name strings. Also from RDS specification, PS is usually a single
44    eight character text. However, it is also possible to find receivers
45    which can scroll strings sized as 8 x N characters. So, this control
46    must be configured with steps of 8 characters. The result is it must
47    always contain a string with size multiple of 8.
48
49``V4L2_CID_RDS_RX_RADIO_TEXT (string)``
50    Gets the Radio Text info. It is a textual description of what is
51    being broadcasted. RDS Radio Text can be applied when broadcaster
52    wishes to transmit longer PS names, programme-related information or
53    any other text. In these cases, RadioText can be used in addition to
54    ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is
55    also fully described in Annex E of :ref:`iec62106`. The length of
56    Radio Text strings depends on which RDS Block is being used to
57    transmit it, either 32 (2A block) or 64 (2B block). However, it is
58    also possible to find receivers which can scroll strings sized as 32
59    x N or 64 x N characters. So, this control must be configured with
60    steps of 32 or 64 characters. The result is it must always contain a
61    string with size multiple of 32 or 64.
62
63``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
64    If set, then a traffic announcement is in progress.
65
66``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
67    If set, then the tuned programme carries traffic announcements.
68
69``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)``
70    If set, then this channel broadcasts music. If cleared, then it
71    broadcasts speech. If the transmitter doesn't make this distinction,
72    then it will be set.
73
74``V4L2_CID_TUNE_DEEMPHASIS``
75    (enum)
76
77enum v4l2_deemphasis -
78    Configures the de-emphasis value for reception. A de-emphasis filter
79    is applied to the broadcast to accentuate the high audio
80    frequencies. Depending on the region, a time constant of either 50
81    or 75 useconds is used. The enum v4l2_deemphasis defines possible
82    values for de-emphasis. Here they are:
83
84
85
86.. flat-table::
87    :header-rows:  0
88    :stub-columns: 0
89
90    * - ``V4L2_DEEMPHASIS_DISABLED``
91      - No de-emphasis is applied.
92    * - ``V4L2_DEEMPHASIS_50_uS``
93      - A de-emphasis of 50 uS is used.
94    * - ``V4L2_DEEMPHASIS_75_uS``
95      - A de-emphasis of 75 uS is used.
96