1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 2
3 .. _tuner: 3 .. _tuner:
4 4
5 ********************* 5 *********************
6 Tuners and Modulators 6 Tuners and Modulators
7 ********************* 7 *********************
8 8
9 9
10 Tuners 10 Tuners
11 ====== 11 ======
12 12
13 Video input devices can have one or more tuner 13 Video input devices can have one or more tuners demodulating a RF
14 signal. Each tuner is associated with one or m 14 signal. Each tuner is associated with one or more video inputs,
15 depending on the number of RF connectors on th 15 depending on the number of RF connectors on the tuner. The ``type``
16 field of the respective struct :c:type:`v4l2_i 16 field of the respective struct :c:type:`v4l2_input`
17 returned by the :ref:`VIDIOC_ENUMINPUT` ioctl 17 returned by the :ref:`VIDIOC_ENUMINPUT` ioctl is
18 set to ``V4L2_INPUT_TYPE_TUNER`` and its ``tun 18 set to ``V4L2_INPUT_TYPE_TUNER`` and its ``tuner`` field contains the
19 index number of the tuner. 19 index number of the tuner.
20 20
21 Radio input devices have exactly one tuner wit 21 Radio input devices have exactly one tuner with index zero, no video
22 inputs. 22 inputs.
23 23
24 To query and change tuner properties applicati 24 To query and change tuner properties applications use the
25 :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` and 25 :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` and
26 :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` ioctls, 26 :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` ioctls, respectively. The
27 struct :c:type:`v4l2_tuner` returned by :ref:` 27 struct :c:type:`v4l2_tuner` returned by :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>`
28 also contains signal status information applic 28 also contains signal status information applicable when the tuner of the
29 current video or radio input is queried. 29 current video or radio input is queried.
30 30
31 .. note:: 31 .. note::
32 32
33 :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` does 33 :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` does not switch the
34 current tuner, when there is more than one. 34 current tuner, when there is more than one. The tuner is solely
35 determined by the current video input. Driv 35 determined by the current video input. Drivers must support both ioctls
36 and set the ``V4L2_CAP_TUNER`` flag in the 36 and set the ``V4L2_CAP_TUNER`` flag in the struct :c:type:`v4l2_capability`
37 returned by the :ref:`VIDIOC_QUERYCAP` ioct 37 returned by the :ref:`VIDIOC_QUERYCAP` ioctl when the
38 device has one or more tuners. 38 device has one or more tuners.
39 39
40 40
41 Modulators 41 Modulators
42 ========== 42 ==========
43 43
44 Video output devices can have one or more modu 44 Video output devices can have one or more modulators, that modulate a
45 video signal for radiation or connection to th 45 video signal for radiation or connection to the antenna input of a TV
46 set or video recorder. Each modulator is assoc 46 set or video recorder. Each modulator is associated with one or more
47 video outputs, depending on the number of RF c 47 video outputs, depending on the number of RF connectors on the
48 modulator. The ``type`` field of the respectiv 48 modulator. The ``type`` field of the respective struct
49 :c:type:`v4l2_output` returned by the 49 :c:type:`v4l2_output` returned by the
50 :ref:`VIDIOC_ENUMOUTPUT` ioctl is set to 50 :ref:`VIDIOC_ENUMOUTPUT` ioctl is set to
51 ``V4L2_OUTPUT_TYPE_MODULATOR`` and its ``modul 51 ``V4L2_OUTPUT_TYPE_MODULATOR`` and its ``modulator`` field contains the
52 index number of the modulator. 52 index number of the modulator.
53 53
54 Radio output devices have exactly one modulato 54 Radio output devices have exactly one modulator with index zero, no
55 video outputs. 55 video outputs.
56 56
57 A video or radio device cannot support both a 57 A video or radio device cannot support both a tuner and a modulator. Two
58 separate device nodes will have to be used for 58 separate device nodes will have to be used for such hardware, one that
59 supports the tuner functionality and one that 59 supports the tuner functionality and one that supports the modulator
60 functionality. The reason is a limitation with 60 functionality. The reason is a limitation with the
61 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` 61 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl where you
62 cannot specify whether the frequency is for a 62 cannot specify whether the frequency is for a tuner or a modulator.
63 63
64 To query and change modulator properties appli 64 To query and change modulator properties applications use the
65 :ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` 65 :ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` and
66 :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` 66 :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl. Note that
67 :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` 67 :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` does not switch the current modulator, when there
68 is more than one at all. The modulator is sole 68 is more than one at all. The modulator is solely determined by the
69 current video output. Drivers must support bot 69 current video output. Drivers must support both ioctls and set the
70 ``V4L2_CAP_MODULATOR`` flag in the struct 70 ``V4L2_CAP_MODULATOR`` flag in the struct
71 :c:type:`v4l2_capability` returned by the 71 :c:type:`v4l2_capability` returned by the
72 :ref:`VIDIOC_QUERYCAP` ioctl when the device h 72 :ref:`VIDIOC_QUERYCAP` ioctl when the device has
73 one or more modulators. 73 one or more modulators.
74 74
75 75
76 Radio Frequency 76 Radio Frequency
77 =============== 77 ===============
78 78
79 To get and set the tuner or modulator radio fr 79 To get and set the tuner or modulator radio frequency applications use
80 the :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUEN 80 the :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
81 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` 81 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl which both take
82 a pointer to a struct :c:type:`v4l2_frequency` 82 a pointer to a struct :c:type:`v4l2_frequency`. These
83 ioctls are used for TV and radio devices alike 83 ioctls are used for TV and radio devices alike. Drivers must support
84 both ioctls when the tuner or modulator ioctls 84 both ioctls when the tuner or modulator ioctls are supported, or when
85 the device is a radio device. 85 the device is a radio device.
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