1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _fm-rx-controls: 5 6***************************** 7FM Receiver Control Reference 8***************************** 9 10The FM Receiver (FM_RX) class includes controls for common features of 11FM Reception capable devices. 12 13 14.. _fm-rx-control-id: 15 16FM_RX Control IDs 17================= 18 19``V4L2_CID_FM_RX_CLASS (class)`` 20 The FM_RX class descriptor. Calling 21 :ref:`VIDIOC_QUERYCTRL` for this control will 22 return a description of this control class. 23 24``V4L2_CID_RDS_RECEPTION (boolean)`` 25 Enables/disables RDS reception by the radio tuner 26 27``V4L2_CID_RDS_RX_PTY (integer)`` 28 Gets RDS Programme Type field. This encodes up to 31 pre-defined 29 programme types. 30 31``V4L2_CID_RDS_RX_PS_NAME (string)`` 32 Gets the Programme Service name (PS_NAME). It is intended for 33 static display on a receiver. It is the primary aid to listeners in 34 programme service identification and selection. In Annex E of 35 :ref:`iec62106`, the RDS specification, there is a full 36 description of the correct character encoding for Programme Service 37 name strings. Also from RDS specification, PS is usually a single 38 eight character text. However, it is also possible to find receivers 39 which can scroll strings sized as 8 x N characters. So, this control 40 must be configured with steps of 8 characters. The result is it must 41 always contain a string with size multiple of 8. 42 43``V4L2_CID_RDS_RX_RADIO_TEXT (string)`` 44 Gets the Radio Text info. It is a textual description of what is 45 being broadcasted. RDS Radio Text can be applied when broadcaster 46 wishes to transmit longer PS names, programme-related information or 47 any other text. In these cases, RadioText can be used in addition to 48 ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is 49 also fully described in Annex E of :ref:`iec62106`. The length of 50 Radio Text strings depends on which RDS Block is being used to 51 transmit it, either 32 (2A block) or 64 (2B block). However, it is 52 also possible to find receivers which can scroll strings sized as 32 53 x N or 64 x N characters. So, this control must be configured with 54 steps of 32 or 64 characters. The result is it must always contain a 55 string with size multiple of 32 or 64. 56 57``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)`` 58 If set, then a traffic announcement is in progress. 59 60``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)`` 61 If set, then the tuned programme carries traffic announcements. 62 63``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)`` 64 If set, then this channel broadcasts music. If cleared, then it 65 broadcasts speech. If the transmitter doesn't make this distinction, 66 then it will be set. 67 68``V4L2_CID_TUNE_DEEMPHASIS (enum)`` 69 Configures the de-emphasis value for reception. A de-emphasis filter 70 is applied to the broadcast to accentuate the high audio 71 frequencies. Depending on the region, a time constant of either 50 72 or 75 microseconds is used. The enum v4l2_deemphasis defines possible 73 values for de-emphasis. They are: 74 75.. flat-table:: 76 :header-rows: 0 77 :stub-columns: 0 78 79 * - ``V4L2_DEEMPHASIS_DISABLED`` 80 - No de-emphasis is applied. 81 * - ``V4L2_DEEMPHASIS_50_uS`` 82 - A de-emphasis of 50 uS is used. 83 * - ``V4L2_DEEMPHASIS_75_uS`` 84 - A de-emphasis of 75 uS is used. 85