Documentation/media/uapi/v4l/vidioc-g-modulator.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_G_MODULATOR:
   4
   5 ********************************************
   6 ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR
   7 ********************************************
   8
   9 Name
  10 ====
  11
  12 VIDIOC_G_MODULATOR - VIDIOC_S_MODULATOR - Get or set modulator attributes
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, VIDIOC_G_MODULATOR, struct v4l2_modulator *argp )
  19     :name: VIDIOC_G_MODULATOR
  20
  21 .. c:function:: int ioctl( int fd, VIDIOC_S_MODULATOR, const struct v4l2_modulator *argp )
  22     :name: VIDIOC_S_MODULATOR
  23
  24
  25 Arguments
  26 =========
  27
  28 ``fd``
  29     File descriptor returned by :ref:`open() <func-open>`.
  30
  31 ``argp``
  32
  33
  34 Description
  35 ===========
  36
  37 To query the attributes of a modulator applications initialize the
  38 ``index`` field and zero out the ``reserved`` array of a struct
  39 :c:type:`v4l2_modulator` and call the
  40 :ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl with a pointer to this structure. Drivers
  41 fill the rest of the structure or return an ``EINVAL`` error code when the
  42 index is out of bounds. To enumerate all modulators applications shall
  43 begin at index zero, incrementing by one until the driver returns
  44 EINVAL.
  45
  46 Modulators have two writable properties, an audio modulation set and the
  47 radio frequency. To change the modulated audio subprograms, applications
  48 initialize the ``index`` and ``txsubchans`` fields and the ``reserved``
  49 array and call the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl. Drivers may choose a
  50 different audio modulation if the request cannot be satisfied. However
  51 this is a write-only ioctl, it does not return the actual audio
  52 modulation selected.
  53
  54 :ref:`SDR <sdr>` specific modulator types are ``V4L2_TUNER_SDR`` and
  55 ``V4L2_TUNER_RF``. For SDR devices ``txsubchans`` field must be
  56 initialized to zero. The term 'modulator' means SDR transmitter in this
  57 context.
  58
  59 To change the radio frequency the
  60 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl is available.
  61
  62
  63 .. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{3.0cm}|
  64
  65 .. c:type:: v4l2_modulator
  66
  67 .. flat-table:: struct v4l2_modulator
  68     :header-rows:  0
  69     :stub-columns: 0
  70     :widths:       1 1 2 1 1
  71
  72     * - __u32
  73       - ``index``
  74       - Identifies the modulator, set by the application.
  75     * - __u8
  76       - ``name``\ [32]
  77       - Name of the modulator, a NUL-terminated ASCII string.
  78
  79         This information is intended for the user.
  80     * - __u32
  81       - ``capability``
  82       - Modulator capability flags. No flags are defined for this field,
  83         the tuner flags in struct :c:type:`v4l2_tuner` are
  84         used accordingly. The audio flags indicate the ability to encode
  85         audio subprograms. They will *not* change for example with the
  86         current video standard.
  87     * - __u32
  88       - ``rangelow``
  89       - The lowest tunable frequency in units of 62.5 KHz, or if the
  90         ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of
  91         62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is
  92         set, in units of 1 Hz.
  93     * - __u32
  94       - ``rangehigh``
  95       - The highest tunable frequency in units of 62.5 KHz, or if the
  96         ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of
  97         62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is
  98         set, in units of 1 Hz.
  99     * - __u32
 100       - ``txsubchans``
 101       - With this field applications can determine how audio sub-carriers
 102         shall be modulated. It contains a set of flags as defined in
 103         :ref:`modulator-txsubchans`.
 104
 105         .. note::
 106
 107            The tuner ``rxsubchans`` flags  are reused, but the
 108            semantics are different. Video output devices
 109            are assumed to have an analog or PCM audio input with 1-3
 110            channels. The ``txsubchans`` flags select one or more channels
 111            for modulation, together with some audio subprogram indicator,
 112            for example, a stereo pilot tone.
 113     * - __u32
 114       - ``type``
 115       - :cspan:`2` Type of the modulator, see :c:type:`v4l2_tuner_type`.
 116     * - __u32
 117       - ``reserved``\ [3]
 118       - Reserved for future extensions.
 119
 120         Drivers and applications must set the array to zero.
 121
 122
 123
 124 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
 125
 126 .. _modulator-txsubchans:
 127
 128 .. flat-table:: Modulator Audio Transmission Flags
 129     :header-rows:  0
 130     :stub-columns: 0
 131     :widths:       3 1 4
 132
 133     * - ``V4L2_TUNER_SUB_MONO``
 134       - 0x0001
 135       - Modulate channel 1 as mono audio, when the input has more
 136         channels, a down-mix of channel 1 and 2. This flag does not
 137         combine with ``V4L2_TUNER_SUB_STEREO`` or
 138         ``V4L2_TUNER_SUB_LANG1``.
 139     * - ``V4L2_TUNER_SUB_STEREO``
 140       - 0x0002
 141       - Modulate channel 1 and 2 as left and right channel of a stereo
 142         audio signal. When the input has only one channel or two channels
 143         and ``V4L2_TUNER_SUB_SAP`` is also set, channel 1 is encoded as
 144         left and right channel. This flag does not combine with
 145         ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_LANG1``. When the
 146         driver does not support stereo audio it shall fall back to mono.
 147     * - ``V4L2_TUNER_SUB_LANG1``
 148       - 0x0008
 149       - Modulate channel 1 and 2 as primary and secondary language of a
 150         bilingual audio signal. When the input has only one channel it is
 151         used for both languages. It is not possible to encode the primary
 152         or secondary language only. This flag does not combine with
 153         ``V4L2_TUNER_SUB_MONO``, ``V4L2_TUNER_SUB_STEREO`` or
 154         ``V4L2_TUNER_SUB_SAP``. If the hardware does not support the
 155         respective audio matrix, or the current video standard does not
 156         permit bilingual audio the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall
 157         return an ``EINVAL`` error code and the driver shall fall back to mono
 158         or stereo mode.
 159     * - ``V4L2_TUNER_SUB_LANG2``
 160       - 0x0004
 161       - Same effect as ``V4L2_TUNER_SUB_SAP``.
 162     * - ``V4L2_TUNER_SUB_SAP``
 163       - 0x0004
 164       - When combined with ``V4L2_TUNER_SUB_MONO`` the first channel is
 165         encoded as mono audio, the last channel as Second Audio Program.
 166         When the input has only one channel it is used for both audio
 167         tracks. When the input has three channels the mono track is a
 168         down-mix of channel 1 and 2. When combined with
 169         ``V4L2_TUNER_SUB_STEREO`` channel 1 and 2 are encoded as left and
 170         right stereo audio, channel 3 as Second Audio Program. When the
 171         input has only two channels, the first is encoded as left and
 172         right channel and the second as SAP. When the input has only one
 173         channel it is used for all audio tracks. It is not possible to
 174         encode a Second Audio Program only. This flag must combine with
 175         ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the
 176         hardware does not support the respective audio matrix, or the
 177         current video standard does not permit SAP the
 178         :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall return an ``EINVAL`` error code and
 179         driver shall fall back to mono or stereo mode.
 180     * - ``V4L2_TUNER_SUB_RDS``
 181       - 0x0010
 182       - Enable the RDS encoder for a radio FM transmitter.
 183
 184
 185 Return Value
 186 ============
 187
 188 On success 0 is returned, on error -1 and the ``errno`` variable is set
 189 appropriately. The generic error codes are described at the
 190 :ref:`Generic Error Codes <gen-errors>` chapter.
 191
 192 EINVAL
 193     The struct :c:type:`v4l2_modulator` ``index`` is
 194     out of bounds.