| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| |
| .. _fm-tx-controls: |
| |
| ******************************** |
| FM Transmitter Control Reference |
| ******************************** |
| |
| The FM Transmitter (FM_TX) class includes controls for common features |
| of FM transmissions capable devices. Currently this class includes |
| parameters for audio compression, pilot tone generation, audio deviation |
| limiter, RDS transmission and tuning power features. |
| |
| |
| .. _fm-tx-control-id: |
| |
| FM_TX Control IDs |
| ================= |
| |
| ``V4L2_CID_FM_TX_CLASS (class)`` |
| The FM_TX class descriptor. Calling |
| :ref:`VIDIOC_QUERYCTRL` for this control will |
| return a description of this control class. |
| |
| ``V4L2_CID_RDS_TX_DEVIATION (integer)`` |
| Configures RDS signal frequency deviation level in Hz. The range and |
| step are driver-specific. |
| |
| ``V4L2_CID_RDS_TX_PI (integer)`` |
| Sets the RDS Programme Identification field for transmission. |
| |
| ``V4L2_CID_RDS_TX_PTY (integer)`` |
| Sets the RDS Programme Type field for transmission. This encodes up |
| to 31 pre-defined programme types. |
| |
| ``V4L2_CID_RDS_TX_PS_NAME (string)`` |
| Sets the Programme Service name (PS_NAME) for transmission. It is |
| intended for static display on a receiver. It is the primary aid to |
| listeners in programme service identification and selection. In |
| Annex E of :ref:`iec62106`, the RDS specification, there is a full |
| description of the correct character encoding for Programme Service |
| name strings. Also from RDS specification, PS is usually a single |
| eight character text. However, it is also possible to find receivers |
| which can scroll strings sized as 8 x N characters. So, this control |
| must be configured with steps of 8 characters. The result is it must |
| always contain a string with size multiple of 8. |
| |
| ``V4L2_CID_RDS_TX_RADIO_TEXT (string)`` |
| Sets the Radio Text info for transmission. It is a textual |
| description of what is being broadcasted. RDS Radio Text can be |
| applied when broadcaster wishes to transmit longer PS names, |
| programme-related information or any other text. In these cases, |
| RadioText should be used in addition to ``V4L2_CID_RDS_TX_PS_NAME``. |
| The encoding for Radio Text strings is also fully described in Annex |
| E of :ref:`iec62106`. The length of Radio Text strings depends on |
| which RDS Block is being used to transmit it, either 32 (2A block) |
| or 64 (2B block). However, it is also possible to find receivers |
| which can scroll strings sized as 32 x N or 64 x N characters. So, |
| this control must be configured with steps of 32 or 64 characters. |
| The result is it must always contain a string with size multiple of |
| 32 or 64. |
| |
| ``V4L2_CID_RDS_TX_MONO_STEREO (boolean)`` |
| Sets the Mono/Stereo bit of the Decoder Identification code. If set, |
| then the audio was recorded as stereo. |
| |
| ``V4L2_CID_RDS_TX_ARTIFICIAL_HEAD (boolean)`` |
| Sets the |
| `Artificial Head <http://en.wikipedia.org/wiki/Artificial_head>`__ |
| bit of the Decoder Identification code. If set, then the audio was |
| recorded using an artificial head. |
| |
| ``V4L2_CID_RDS_TX_COMPRESSED (boolean)`` |
| Sets the Compressed bit of the Decoder Identification code. If set, |
| then the audio is compressed. |
| |
| ``V4L2_CID_RDS_TX_DYNAMIC_PTY (boolean)`` |
| Sets the Dynamic PTY bit of the Decoder Identification code. If set, |
| then the PTY code is dynamically switched. |
| |
| ``V4L2_CID_RDS_TX_TRAFFIC_ANNOUNCEMENT (boolean)`` |
| If set, then a traffic announcement is in progress. |
| |
| ``V4L2_CID_RDS_TX_TRAFFIC_PROGRAM (boolean)`` |
| If set, then the tuned programme carries traffic announcements. |
| |
| ``V4L2_CID_RDS_TX_MUSIC_SPEECH (boolean)`` |
| If set, then this channel broadcasts music. If cleared, then it |
| broadcasts speech. If the transmitter doesn't make this distinction, |
| then it should be set. |
| |
| ``V4L2_CID_RDS_TX_ALT_FREQS_ENABLE (boolean)`` |
| If set, then transmit alternate frequencies. |
| |
| ``V4L2_CID_RDS_TX_ALT_FREQS (__u32 array)`` |
| The alternate frequencies in kHz units. The RDS standard allows for |
| up to 25 frequencies to be defined. Drivers may support fewer |
| frequencies so check the array size. |
| |
| ``V4L2_CID_AUDIO_LIMITER_ENABLED (boolean)`` |
| Enables or disables the audio deviation limiter feature. The limiter |
| is useful when trying to maximize the audio volume, minimize |
| receiver-generated distortion and prevent overmodulation. |
| |
| ``V4L2_CID_AUDIO_LIMITER_RELEASE_TIME (integer)`` |
| Sets the audio deviation limiter feature release time. Unit is in |
| useconds. Step and range are driver-specific. |
| |
| ``V4L2_CID_AUDIO_LIMITER_DEVIATION (integer)`` |
| Configures audio frequency deviation level in Hz. The range and step |
| are driver-specific. |
| |
| ``V4L2_CID_AUDIO_COMPRESSION_ENABLED (boolean)`` |
| Enables or disables the audio compression feature. This feature |
| amplifies signals below the threshold by a fixed gain and compresses |
| audio signals above the threshold by the ratio of Threshold/(Gain + |
| Threshold). |
| |
| ``V4L2_CID_AUDIO_COMPRESSION_GAIN (integer)`` |
| Sets the gain for audio compression feature. It is a dB value. The |
| range and step are driver-specific. |
| |
| ``V4L2_CID_AUDIO_COMPRESSION_THRESHOLD (integer)`` |
| Sets the threshold level for audio compression freature. It is a dB |
| value. The range and step are driver-specific. |
| |
| ``V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME (integer)`` |
| Sets the attack time for audio compression feature. It is a useconds |
| value. The range and step are driver-specific. |
| |
| ``V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME (integer)`` |
| Sets the release time for audio compression feature. It is a |
| useconds value. The range and step are driver-specific. |
| |
| ``V4L2_CID_PILOT_TONE_ENABLED (boolean)`` |
| Enables or disables the pilot tone generation feature. |
| |
| ``V4L2_CID_PILOT_TONE_DEVIATION (integer)`` |
| Configures pilot tone frequency deviation level. Unit is in Hz. The |
| range and step are driver-specific. |
| |
| ``V4L2_CID_PILOT_TONE_FREQUENCY (integer)`` |
| Configures pilot tone frequency value. Unit is in Hz. The range and |
| step are driver-specific. |
| |
| ``V4L2_CID_TUNE_PREEMPHASIS`` |
| (enum) |
| |
| enum v4l2_preemphasis - |
| Configures the pre-emphasis value for broadcasting. A pre-emphasis |
| filter is applied to the broadcast to accentuate the high audio |
| frequencies. Depending on the region, a time constant of either 50 |
| or 75 useconds is used. The enum v4l2_preemphasis defines possible |
| values for pre-emphasis. Here they are: |
| |
| |
| |
| .. flat-table:: |
| :header-rows: 0 |
| :stub-columns: 0 |
| |
| * - ``V4L2_PREEMPHASIS_DISABLED`` |
| - No pre-emphasis is applied. |
| * - ``V4L2_PREEMPHASIS_50_uS`` |
| - A pre-emphasis of 50 uS is used. |
| * - ``V4L2_PREEMPHASIS_75_uS`` |
| - A pre-emphasis of 75 uS is used. |
| |
| |
| |
| ``V4L2_CID_TUNE_POWER_LEVEL (integer)`` |
| Sets the output power level for signal transmission. Unit is in |
| dBuV. Range and step are driver-specific. |
| |
| ``V4L2_CID_TUNE_ANTENNA_CAPACITOR (integer)`` |
| This selects the value of antenna tuning capacitor manually or |
| automatically if set to zero. Unit, range and step are |
| driver-specific. |
| |
| For more details about RDS specification, refer to :ref:`iec62106` |
| document, from CENELEC. |
