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 .. c:function:: int ioctl( int fd, VIDIOC_ENUM_FREQ_BANDS, struct v4l2_frequency_band *argp )
19 :name: VIDIOC_ENUM_FREQ_BANDS
26 File descriptor returned by :ref:`open() <func-open>`.
34 Enumerates the frequency bands that a tuner or modulator supports. To do
35 this applications initialize the ``tuner``, ``type`` and ``index``
36 fields, and zero out the ``reserved`` array of a struct
37 :c:type:`v4l2_frequency_band` and call the
38 :ref:`VIDIOC_ENUM_FREQ_BANDS` ioctl with a pointer to this structure.
40 This ioctl is supported if the ``V4L2_TUNER_CAP_FREQ_BANDS`` capability
41 of the corresponding tuner/modulator is set.
44 .. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{3.0cm}|
46 .. c:type:: v4l2_frequency_band
48 .. flat-table:: struct v4l2_frequency_band
60 - The tuner or modulator index number. This is the same value as in
61 the struct :c:type:`v4l2_input` ``tuner`` field and
62 the struct :c:type:`v4l2_tuner` ``index`` field, or
63 the struct :c:type:`v4l2_output` ``modulator`` field
64 and the struct :c:type:`v4l2_modulator` ``index``
73 - The tuner type. This is the same value as in the struct
74 :c:type:`v4l2_tuner` ``type`` field. The type must be
75 set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
76 to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
77 ``V4L2_TUNER_RADIO`` for modulators (currently only radio
78 modulators are supported). See :c:type:`v4l2_tuner_type`
86 - Identifies the frequency band, set by the application.
94 - :cspan:`2` The tuner/modulator capability flags for this
95 frequency band, see :ref:`tuner-capability`. The
96 ``V4L2_TUNER_CAP_LOW`` or ``V4L2_TUNER_CAP_1HZ`` capability must
97 be the same for all frequency bands of the selected
98 tuner/modulator. So either all bands have that capability set, or
99 none of them have that capability.
107 - :cspan:`2` The lowest tunable frequency in units of 62.5 kHz, or
108 if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units
109 of 62.5 Hz, for this frequency band. A 1 Hz unit is used when the
110 ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
118 - :cspan:`2` The highest tunable frequency in units of 62.5 kHz,
119 or if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in
120 units of 62.5 Hz, for this frequency band. A 1 Hz unit is used
121 when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
129 - :cspan:`2` The supported modulation systems of this frequency
130 band. See :ref:`band-modulation`.
134 Currently only one modulation system per frequency band
135 is supported. More work will need to be done if multiple
136 modulation systems are possible. Contact the linux-media
138 (`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
139 if you need such functionality.
147 - Reserved for future extensions.
149 Applications and drivers must set the array to zero.
153 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
157 .. flat-table:: Band Modulation Systems
165 - ``V4L2_BAND_MODULATION_VSB``
169 - Vestigial Sideband modulation, used for analog TV.
173 - ``V4L2_BAND_MODULATION_FM``
177 - Frequency Modulation, commonly used for analog radio.
181 - ``V4L2_BAND_MODULATION_AM``
185 - Amplitude Modulation, commonly used for analog radio.
191 On success 0 is returned, on error -1 and the ``errno`` variable is set
192 appropriately. The generic error codes are described at the
193 :ref:`Generic Error Codes <gen-errors>` chapter.
196 The ``tuner`` or ``index`` is out of bounds or the ``type`` field is