1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 3.. _fm-tx-controls: 4 5******************************** 6FM Transmitter Control Reference 7******************************** 8 9The FM Transmitter (FM_TX) class includes controls for common features 10of FM transmissions capable devices. Currently this class includes 11parameters for audio compression, pilot tone generation, audio deviation 12limiter, RDS transmission and tuning power features. 13 14 15.. _fm-tx-control-id: 16 17FM_TX Control IDs 18================= 19 20``V4L2_CID_FM_TX_CLASS (class)`` 21 The FM_TX class descriptor. Calling 22 :ref:`VIDIOC_QUERYCTRL` for this control will 23 return a description of this control class. 24 25``V4L2_CID_RDS_TX_DEVIATION (integer)`` 26 Configures RDS signal frequency deviation level in Hz. The range and 27 step are driver-specific. 28 29``V4L2_CID_RDS_TX_PI (integer)`` 30 Sets the RDS Programme Identification field for transmission. 31 32``V4L2_CID_RDS_TX_PTY (integer)`` 33 Sets the RDS Programme Type field for transmission. This encodes up 34 to 31 pre-defined programme types. 35 36``V4L2_CID_RDS_TX_PS_NAME (string)`` 37 Sets the Programme Service name (PS_NAME) for transmission. It is 38 intended for static display on a receiver. It is the primary aid to 39 listeners in programme service identification and selection. In 40 Annex E of :ref:`iec62106`, the RDS specification, there is a full 41 description of the correct character encoding for Programme Service 42 name strings. Also from RDS specification, PS is usually a single 43 eight character text. However, it is also possible to find receivers 44 which can scroll strings sized as 8 x N characters. So, this control 45 must be configured with steps of 8 characters. The result is it must 46 always contain a string with size multiple of 8. 47 48``V4L2_CID_RDS_TX_RADIO_TEXT (string)`` 49 Sets the Radio Text info for transmission. It is a textual 50 description of what is being broadcasted. RDS Radio Text can be 51 applied when broadcaster wishes to transmit longer PS names, 52 programme-related information or any other text. In these cases, 53 RadioText should be used in addition to ``V4L2_CID_RDS_TX_PS_NAME``. 54 The encoding for Radio Text strings is also fully described in Annex 55 E of :ref:`iec62106`. The length of Radio Text strings depends on 56 which RDS Block is being used to transmit it, either 32 (2A block) 57 or 64 (2B block). However, it is also possible to find receivers 58 which can scroll strings sized as 32 x N or 64 x N characters. So, 59 this control must be configured with steps of 32 or 64 characters. 60 The result is it must always contain a string with size multiple of 61 32 or 64. 62 63``V4L2_CID_RDS_TX_MONO_STEREO (boolean)`` 64 Sets the Mono/Stereo bit of the Decoder Identification code. If set, 65 then the audio was recorded as stereo. 66 67``V4L2_CID_RDS_TX_ARTIFICIAL_HEAD (boolean)`` 68 Sets the 69 `Artificial Head <http://en.wikipedia.org/wiki/Artificial_head>`__ 70 bit of the Decoder Identification code. If set, then the audio was 71 recorded using an artificial head. 72 73``V4L2_CID_RDS_TX_COMPRESSED (boolean)`` 74 Sets the Compressed bit of the Decoder Identification code. If set, 75 then the audio is compressed. 76 77``V4L2_CID_RDS_TX_DYNAMIC_PTY (boolean)`` 78 Sets the Dynamic PTY bit of the Decoder Identification code. If set, 79 then the PTY code is dynamically switched. 80 81``V4L2_CID_RDS_TX_TRAFFIC_ANNOUNCEMENT (boolean)`` 82 If set, then a traffic announcement is in progress. 83 84``V4L2_CID_RDS_TX_TRAFFIC_PROGRAM (boolean)`` 85 If set, then the tuned programme carries traffic announcements. 86 87``V4L2_CID_RDS_TX_MUSIC_SPEECH (boolean)`` 88 If set, then this channel broadcasts music. If cleared, then it 89 broadcasts speech. If the transmitter doesn't make this distinction, 90 then it should be set. 91 92``V4L2_CID_RDS_TX_ALT_FREQS_ENABLE (boolean)`` 93 If set, then transmit alternate frequencies. 94 95``V4L2_CID_RDS_TX_ALT_FREQS (__u32 array)`` 96 The alternate frequencies in kHz units. The RDS standard allows for 97 up to 25 frequencies to be defined. Drivers may support fewer 98 frequencies so check the array size. 99 100``V4L2_CID_AUDIO_LIMITER_ENABLED (boolean)`` 101 Enables or disables the audio deviation limiter feature. The limiter 102 is useful when trying to maximize the audio volume, minimize 103 receiver-generated distortion and prevent overmodulation. 104 105``V4L2_CID_AUDIO_LIMITER_RELEASE_TIME (integer)`` 106 Sets the audio deviation limiter feature release time. Unit is in 107 useconds. Step and range are driver-specific. 108 109``V4L2_CID_AUDIO_LIMITER_DEVIATION (integer)`` 110 Configures audio frequency deviation level in Hz. The range and step 111 are driver-specific. 112 113``V4L2_CID_AUDIO_COMPRESSION_ENABLED (boolean)`` 114 Enables or disables the audio compression feature. This feature 115 amplifies signals below the threshold by a fixed gain and compresses 116 audio signals above the threshold by the ratio of Threshold/(Gain + 117 Threshold). 118 119``V4L2_CID_AUDIO_COMPRESSION_GAIN (integer)`` 120 Sets the gain for audio compression feature. It is a dB value. The 121 range and step are driver-specific. 122 123``V4L2_CID_AUDIO_COMPRESSION_THRESHOLD (integer)`` 124 Sets the threshold level for audio compression freature. It is a dB 125 value. The range and step are driver-specific. 126 127``V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME (integer)`` 128 Sets the attack time for audio compression feature. It is a useconds 129 value. The range and step are driver-specific. 130 131``V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME (integer)`` 132 Sets the release time for audio compression feature. It is a 133 useconds value. The range and step are driver-specific. 134 135``V4L2_CID_PILOT_TONE_ENABLED (boolean)`` 136 Enables or disables the pilot tone generation feature. 137 138``V4L2_CID_PILOT_TONE_DEVIATION (integer)`` 139 Configures pilot tone frequency deviation level. Unit is in Hz. The 140 range and step are driver-specific. 141 142``V4L2_CID_PILOT_TONE_FREQUENCY (integer)`` 143 Configures pilot tone frequency value. Unit is in Hz. The range and 144 step are driver-specific. 145 146``V4L2_CID_TUNE_PREEMPHASIS`` 147 (enum) 148 149enum v4l2_preemphasis - 150 Configures the pre-emphasis value for broadcasting. A pre-emphasis 151 filter is applied to the broadcast to accentuate the high audio 152 frequencies. Depending on the region, a time constant of either 50 153 or 75 useconds is used. The enum v4l2_preemphasis defines possible 154 values for pre-emphasis. Here they are: 155 156 157 158.. flat-table:: 159 :header-rows: 0 160 :stub-columns: 0 161 162 * - ``V4L2_PREEMPHASIS_DISABLED`` 163 - No pre-emphasis is applied. 164 * - ``V4L2_PREEMPHASIS_50_uS`` 165 - A pre-emphasis of 50 uS is used. 166 * - ``V4L2_PREEMPHASIS_75_uS`` 167 - A pre-emphasis of 75 uS is used. 168 169 170 171``V4L2_CID_TUNE_POWER_LEVEL (integer)`` 172 Sets the output power level for signal transmission. Unit is in 173 dBuV. Range and step are driver-specific. 174 175``V4L2_CID_TUNE_ANTENNA_CAPACITOR (integer)`` 176 This selects the value of antenna tuning capacitor manually or 177 automatically if set to zero. Unit, range and step are 178 driver-specific. 179 180For more details about RDS specification, refer to :ref:`iec62106` 181document, from CENELEC. 182