1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 2
3 .. _fm-rx-controls: 3 .. _fm-rx-controls:
4 4
5 ***************************** 5 *****************************
6 FM Receiver Control Reference 6 FM Receiver Control Reference
7 ***************************** 7 *****************************
8 8
9 The FM Receiver (FM_RX) class includes control 9 The FM Receiver (FM_RX) class includes controls for common features of
10 FM Reception capable devices. 10 FM Reception capable devices.
11 11
12 12
13 .. _fm-rx-control-id: 13 .. _fm-rx-control-id:
14 14
15 FM_RX Control IDs 15 FM_RX Control IDs
16 ================= 16 =================
17 17
18 ``V4L2_CID_FM_RX_CLASS (class)`` 18 ``V4L2_CID_FM_RX_CLASS (class)``
19 The FM_RX class descriptor. Calling 19 The FM_RX class descriptor. Calling
20 :ref:`VIDIOC_QUERYCTRL` for this control w 20 :ref:`VIDIOC_QUERYCTRL` for this control will
21 return a description of this control class 21 return a description of this control class.
22 22
23 ``V4L2_CID_RDS_RECEPTION (boolean)`` 23 ``V4L2_CID_RDS_RECEPTION (boolean)``
24 Enables/disables RDS reception by the radi 24 Enables/disables RDS reception by the radio tuner
25 25
26 ``V4L2_CID_RDS_RX_PTY (integer)`` 26 ``V4L2_CID_RDS_RX_PTY (integer)``
27 Gets RDS Programme Type field. This encode 27 Gets RDS Programme Type field. This encodes up to 31 pre-defined
28 programme types. 28 programme types.
29 29
30 ``V4L2_CID_RDS_RX_PS_NAME (string)`` 30 ``V4L2_CID_RDS_RX_PS_NAME (string)``
31 Gets the Programme Service name (PS_NAME). 31 Gets the Programme Service name (PS_NAME). It is intended for
32 static display on a receiver. It is the pr 32 static display on a receiver. It is the primary aid to listeners in
33 programme service identification and selec 33 programme service identification and selection. In Annex E of
34 :ref:`iec62106`, the RDS specification, th 34 :ref:`iec62106`, the RDS specification, there is a full
35 description of the correct character encod 35 description of the correct character encoding for Programme Service
36 name strings. Also from RDS specification, 36 name strings. Also from RDS specification, PS is usually a single
37 eight character text. However, it is also 37 eight character text. However, it is also possible to find receivers
38 which can scroll strings sized as 8 x N ch 38 which can scroll strings sized as 8 x N characters. So, this control
39 must be configured with steps of 8 charact 39 must be configured with steps of 8 characters. The result is it must
40 always contain a string with size multiple 40 always contain a string with size multiple of 8.
41 41
42 ``V4L2_CID_RDS_RX_RADIO_TEXT (string)`` 42 ``V4L2_CID_RDS_RX_RADIO_TEXT (string)``
43 Gets the Radio Text info. It is a textual 43 Gets the Radio Text info. It is a textual description of what is
44 being broadcasted. RDS Radio Text can be a 44 being broadcasted. RDS Radio Text can be applied when broadcaster
45 wishes to transmit longer PS names, progra 45 wishes to transmit longer PS names, programme-related information or
46 any other text. In these cases, RadioText 46 any other text. In these cases, RadioText can be used in addition to
47 ``V4L2_CID_RDS_RX_PS_NAME``. The encoding 47 ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is
48 also fully described in Annex E of :ref:`i 48 also fully described in Annex E of :ref:`iec62106`. The length of
49 Radio Text strings depends on which RDS Bl 49 Radio Text strings depends on which RDS Block is being used to
50 transmit it, either 32 (2A block) or 64 (2 50 transmit it, either 32 (2A block) or 64 (2B block). However, it is
51 also possible to find receivers which can 51 also possible to find receivers which can scroll strings sized as 32
52 x N or 64 x N characters. So, this control 52 x N or 64 x N characters. So, this control must be configured with
53 steps of 32 or 64 characters. The result i 53 steps of 32 or 64 characters. The result is it must always contain a
54 string with size multiple of 32 or 64. 54 string with size multiple of 32 or 64.
55 55
56 ``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolea 56 ``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
57 If set, then a traffic announcement is in 57 If set, then a traffic announcement is in progress.
58 58
59 ``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)`` 59 ``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
60 If set, then the tuned programme carries t 60 If set, then the tuned programme carries traffic announcements.
61 61
62 ``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)`` 62 ``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)``
63 If set, then this channel broadcasts music 63 If set, then this channel broadcasts music. If cleared, then it
64 broadcasts speech. If the transmitter does 64 broadcasts speech. If the transmitter doesn't make this distinction,
65 then it will be set. 65 then it will be set.
66 66
67 ``V4L2_CID_TUNE_DEEMPHASIS`` 67 ``V4L2_CID_TUNE_DEEMPHASIS``
68 (enum) 68 (enum)
69 69
70 enum v4l2_deemphasis - 70 enum v4l2_deemphasis -
71 Configures the de-emphasis value for recep 71 Configures the de-emphasis value for reception. A de-emphasis filter
72 is applied to the broadcast to accentuate 72 is applied to the broadcast to accentuate the high audio
73 frequencies. Depending on the region, a ti 73 frequencies. Depending on the region, a time constant of either 50
74 or 75 useconds is used. The enum v4l2_deem 74 or 75 useconds is used. The enum v4l2_deemphasis defines possible
75 values for de-emphasis. Here they are: 75 values for de-emphasis. Here they are:
76 76
77 77
78 78
79 .. flat-table:: 79 .. flat-table::
80 :header-rows: 0 80 :header-rows: 0
81 :stub-columns: 0 81 :stub-columns: 0
82 82
83 * - ``V4L2_DEEMPHASIS_DISABLED`` 83 * - ``V4L2_DEEMPHASIS_DISABLED``
84 - No de-emphasis is applied. 84 - No de-emphasis is applied.
85 * - ``V4L2_DEEMPHASIS_50_uS`` 85 * - ``V4L2_DEEMPHASIS_50_uS``
86 - A de-emphasis of 50 uS is used. 86 - A de-emphasis of 50 uS is used.
87 * - ``V4L2_DEEMPHASIS_75_uS`` 87 * - ``V4L2_DEEMPHASIS_75_uS``
88 - A de-emphasis of 75 uS is used. 88 - A de-emphasis of 75 uS is used.
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