Documentation/media/uapi/v4l/ext-ctrls-fm-rx.rst

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   4 .. Foundation, with no Invariant Sections, no Front-Cover Texts
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   6 .. Documentation/media/uapi/fdl-appendix.rst.
   7 ..
   8 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
   9
  10 .. _fm-rx-controls:
  11
  12 *****************************
  13 FM Receiver Control Reference
  14 *****************************
  15
  16 The FM Receiver (FM_RX) class includes controls for common features of
  17 FM Reception capable devices.
  18
  19
  20 .. _fm-rx-control-id:
  21
  22 FM_RX Control IDs
  23 =================
  24
  25 ``V4L2_CID_FM_RX_CLASS (class)``
  26     The FM_RX class descriptor. Calling
  27     :ref:`VIDIOC_QUERYCTRL` for this control will
  28     return a description of this control class.
  29
  30 ``V4L2_CID_RDS_RECEPTION (boolean)``
  31     Enables/disables RDS reception by the radio tuner
  32
  33 ``V4L2_CID_RDS_RX_PTY (integer)``
  34     Gets RDS Programme Type field. This encodes up to 31 pre-defined
  35     programme types.
  36
  37 ``V4L2_CID_RDS_RX_PS_NAME (string)``
  38     Gets the Programme Service name (PS_NAME). It is intended for
  39     static display on a receiver. It is the primary aid to listeners in
  40     programme service identification and selection. In Annex E of
  41     :ref:`iec62106`, the RDS specification, there is a full
  42     description of the correct character encoding for Programme Service
  43     name strings. Also from RDS specification, PS is usually a single
  44     eight character text. However, it is also possible to find receivers
  45     which can scroll strings sized as 8 x N characters. So, this control
  46     must be configured with steps of 8 characters. The result is it must
  47     always contain a string with size multiple of 8.
  48
  49 ``V4L2_CID_RDS_RX_RADIO_TEXT (string)``
  50     Gets the Radio Text info. It is a textual description of what is
  51     being broadcasted. RDS Radio Text can be applied when broadcaster
  52     wishes to transmit longer PS names, programme-related information or
  53     any other text. In these cases, RadioText can be used in addition to
  54     ``V4L2_CID_RDS_RX_PS_NAME``. The encoding for Radio Text strings is
  55     also fully described in Annex E of :ref:`iec62106`. The length of
  56     Radio Text strings depends on which RDS Block is being used to
  57     transmit it, either 32 (2A block) or 64 (2B block). However, it is
  58     also possible to find receivers which can scroll strings sized as 32
  59     x N or 64 x N characters. So, this control must be configured with
  60     steps of 32 or 64 characters. The result is it must always contain a
  61     string with size multiple of 32 or 64.
  62
  63 ``V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT (boolean)``
  64     If set, then a traffic announcement is in progress.
  65
  66 ``V4L2_CID_RDS_RX_TRAFFIC_PROGRAM (boolean)``
  67     If set, then the tuned programme carries traffic announcements.
  68
  69 ``V4L2_CID_RDS_RX_MUSIC_SPEECH (boolean)``
  70     If set, then this channel broadcasts music. If cleared, then it
  71     broadcasts speech. If the transmitter doesn't make this distinction,
  72     then it will be set.
  73
  74 ``V4L2_CID_TUNE_DEEMPHASIS``
  75     (enum)
  76
  77 enum v4l2_deemphasis -
  78     Configures the de-emphasis value for reception. A de-emphasis filter
  79     is applied to the broadcast to accentuate the high audio
  80     frequencies. Depending on the region, a time constant of either 50
  81     or 75 useconds is used. The enum v4l2_deemphasis defines possible
  82     values for de-emphasis. Here they are:
  83
  84
  85
  86 .. flat-table::
  87     :header-rows:  0
  88     :stub-columns: 0
  89
  90     * - ``V4L2_DEEMPHASIS_DISABLED``
  91       - No de-emphasis is applied.
  92     * - ``V4L2_DEEMPHASIS_50_uS``
  93       - A de-emphasis of 50 uS is used.
  94     * - ``V4L2_DEEMPHASIS_75_uS``
  95       - A de-emphasis of 75 uS is used.