blob: 73aa90b45b34f6b256676b4e9992ec8e7e261116 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
<title>Radio Interface</title>
<para>This interface is intended for AM and FM (analog) radio
receivers and transmitters.</para>
<para>Conventionally V4L2 radio devices are accessed through
character device special files named <filename>/dev/radio</filename>
and <filename>/dev/radio0</filename> to
<filename>/dev/radio63</filename> with major number 81 and minor
numbers 64 to 127.</para>
<section>
<title>Querying Capabilities</title>
<para>Devices supporting the radio interface set the
<constant>V4L2_CAP_RADIO</constant> and
<constant>V4L2_CAP_TUNER</constant> or
<constant>V4L2_CAP_MODULATOR</constant> flag in the
<structfield>capabilities</structfield> field of &v4l2-capability;
returned by the &VIDIOC-QUERYCAP; ioctl. Other combinations of
capability flags are reserved for future extensions.</para>
</section>
<section>
<title>Supplemental Functions</title>
<para>Radio devices can support <link
linkend="control">controls</link>, and must support the <link
linkend="tuner">tuner or modulator</link> ioctls.</para>
<para>They do not support the video input or output, audio input
or output, video standard, cropping and scaling, compression and
streaming parameter, or overlay ioctls. All other ioctls and I/O
methods are reserved for future extensions.</para>
</section>
<section>
<title>Programming</title>
<para>Radio devices may have a couple audio controls (as discussed
in <xref linkend="control" />) such as a volume control, possibly custom
controls. Further all radio devices have one tuner or modulator (these are
discussed in <xref linkend="tuner" />) with index number zero to select
the radio frequency and to determine if a monaural or FM stereo
program is received/emitted. Drivers switch automatically between AM and FM
depending on the selected frequency. The &VIDIOC-G-TUNER; or
&VIDIOC-G-MODULATOR; ioctl
reports the supported frequency range.</para>
</section>
<!--
Local Variables:
mode: sgml
sgml-parent-document: "v4l2.sgml"
indent-tabs-mode: nil
End:
-->
|
