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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2 3.. _fm-rx-controls:4 5*****************************6FM Receiver Control Reference7*****************************8 9The FM Receiver (FM_RX) class includes controls for common features of10FM Reception capable devices.11 12 13.. _fm-rx-control-id:14 15FM_RX Control IDs16=================17 18``V4L2_CID_FM_RX_CLASS (class)``19 The FM_RX class descriptor. Calling20 :ref:`VIDIOC_QUERYCTRL` for this control will21 return a description of this control class.22 23``V4L2_CID_RDS_RECEPTION (boolean)``24 Enables/disables RDS reception by the radio tuner25 26``V4L2_CID_RDS_RX_PTY (integer)``27 Gets RDS Programme Type field. This encodes up to 31 pre-defined28 programme types.29 30``V4L2_CID_RDS_RX_PS_NAME (string)``31 Gets the Programme Service name (PS_NAME). It is intended for32 static display on a receiver. It is the primary aid to listeners in33 programme service identification and selection. In Annex E of34 :ref:`iec62106`, the RDS specification, there is a full35 description of the correct character encoding for Programme Service36 name strings. Also from RDS specification, PS is usually a single37 eight character text. However, it is also possible to find receivers38 which can scroll strings sized as 8 x N characters. So, this control39 must be configured with steps of 8 characters. The result is it must40 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 is44 being broadcasted. RDS Radio Text can be applied when broadcaster45 wishes to transmit longer PS names, programme-related information or46 any other text. In these cases, RadioText can be used in addition to47 ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is48 also fully described in Annex E of :ref:`iec62106`. The length of49 Radio Text strings depends on which RDS Block is being used to50 transmit it, either 32 (2A block) or 64 (2B block). However, it is51 also possible to find receivers which can scroll strings sized as 3252 x N or 64 x N characters. So, this control must be configured with53 steps of 32 or 64 characters. The result is it must always contain a54 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 it64 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 70enum v4l2_deemphasis -71 Configures the de-emphasis value for reception. A de-emphasis filter72 is applied to the broadcast to accentuate the high audio73 frequencies. Depending on the region, a time constant of either 5074 or 75 useconds is used. The enum v4l2_deemphasis defines possible75 values for de-emphasis. Here they are:76 77 78 79.. flat-table::80 :header-rows: 081 :stub-columns: 082 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.89