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