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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _fm-rx-controls:
+
+*****************************
+FM Receiver Control Reference
+*****************************
+
+The FM Receiver (FM_RX) class includes controls for common features of
+FM Reception capable devices.
+
+
+.. _fm-rx-control-id:
+
+FM_RX Control IDs
+=================
+
+``V4L2_CID_FM_RX_CLASS (class)``
+ The FM_RX class descriptor. Calling
+ :ref:`VIDIOC_QUERYCTRL` for this control will
+ return a description of this control class.
+
+``V4L2_CID_RDS_RECEPTION (boolean)``
+ Enables/disables RDS reception by the radio tuner
+
+``V4L2_CID_RDS_RX_PTY (integer)``
+ Gets RDS Programme Type field. This encodes up to 31 pre-defined
+ programme types.
+
+``V4L2_CID_RDS_RX_PS_NAME (string)``
+ Gets the Programme Service name (PS_NAME). 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_RX_RADIO_TEXT (string)``
+ Gets the Radio Text info. 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 can be used in addition to
+ ``V4L2_CID_RDS_RX_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_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
+ If set, then a traffic announcement is in progress.
+
+``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
+ If set, then the tuned programme carries traffic announcements.
+
+``V4L2_CID_RDS_RX_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 will be set.
+
+``V4L2_CID_TUNE_DEEMPHASIS``
+ (enum)
+
+enum v4l2_deemphasis -
+ Configures the de-emphasis value for reception. A de-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_deemphasis defines possible
+ values for de-emphasis. Here they are:
+
+
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+
+ * - ``V4L2_DEEMPHASIS_DISABLED``
+ - No de-emphasis is applied.
+ * - ``V4L2_DEEMPHASIS_50_uS``
+ - A de-emphasis of 50 uS is used.
+ * - ``V4L2_DEEMPHASIS_75_uS``
+ - A de-emphasis of 75 uS is used.