1 .. -*- coding: utf-8; mode: rst -*-
3 .. _VIDIOC_ENUM_FREQ_BANDS:
5 ****************************
6 ioctl VIDIOC_ENUM_FREQ_BANDS
7 ****************************
12 VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
18 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_frequency_band *argp )
25 File descriptor returned by :ref:`open() <func-open>`.
28 VIDIOC_ENUM_FREQ_BANDS
36 Enumerates the frequency bands that a tuner or modulator supports. To do
37 this applications initialize the ``tuner``, ``type`` and ``index``
38 fields, and zero out the ``reserved`` array of a struct
39 :ref:`v4l2_frequency_band <v4l2-frequency-band>` and call the
40 :ref:`VIDIOC_ENUM_FREQ_BANDS` ioctl with a pointer to this structure.
42 This ioctl is supported if the ``V4L2_TUNER_CAP_FREQ_BANDS`` capability
43 of the corresponding tuner/modulator is set.
46 .. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{3.0cm}|
48 .. _v4l2-frequency-band:
50 .. flat-table:: struct v4l2_frequency_band
62 - The tuner or modulator index number. This is the same value as in
63 the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and
64 the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or
65 the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field
66 and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index``
75 - The tuner type. This is the same value as in the struct
76 :ref:`v4l2_tuner <v4l2-tuner>` ``type`` field. The type must be
77 set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
78 to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
79 ``V4L2_TUNER_RADIO`` for modulators (currently only radio
80 modulators are supported). See :ref:`v4l2-tuner-type`
88 - Identifies the frequency band, set by the application.
96 - :cspan:`2` The tuner/modulator capability flags for this
97 frequency band, see :ref:`tuner-capability`. The
98 ``V4L2_TUNER_CAP_LOW`` or ``V4L2_TUNER_CAP_1HZ`` capability must
99 be the same for all frequency bands of the selected
100 tuner/modulator. So either all bands have that capability set, or
101 none of them have that capability.
109 - :cspan:`2` The lowest tunable frequency in units of 62.5 kHz, or
110 if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units
111 of 62.5 Hz, for this frequency band. A 1 Hz unit is used when the
112 ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
120 - :cspan:`2` The highest tunable frequency in units of 62.5 kHz,
121 or if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in
122 units of 62.5 Hz, for this frequency band. A 1 Hz unit is used
123 when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
131 - :cspan:`2` The supported modulation systems of this frequency
132 band. See :ref:`band-modulation`.
136 Currently only one modulation system per frequency band
137 is supported. More work will need to be done if multiple
138 modulation systems are possible. Contact the linux-media
140 (`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
141 if you need such functionality.
149 - Reserved for future extensions.
151 Applications and drivers must set the array to zero.
155 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
159 .. flat-table:: Band Modulation Systems
167 - ``V4L2_BAND_MODULATION_VSB``
171 - Vestigial Sideband modulation, used for analog TV.
175 - ``V4L2_BAND_MODULATION_FM``
179 - Frequency Modulation, commonly used for analog radio.
183 - ``V4L2_BAND_MODULATION_AM``
187 - Amplitude Modulation, commonly used for analog radio.
193 On success 0 is returned, on error -1 and the ``errno`` variable is set
194 appropriately. The generic error codes are described at the
195 :ref:`Generic Error Codes <gen-errors>` chapter.
198 The ``tuner`` or ``index`` is out of bounds or the ``type`` field is