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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_G_MODULATOR: |
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4 | |
5 | ******************************************** | |
6 | ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR | |
7 | ******************************************** | |
8 | ||
9 | *man VIDIOC_G_MODULATOR(2)* | |
10 | ||
11 | VIDIOC_S_MODULATOR | |
12 | Get or set modulator attributes | |
13 | ||
14 | ||
15 | Synopsis | |
16 | ======== | |
17 | ||
18 | .. c:function:: int ioctl( int fd, int request, struct v4l2_modulator *argp ) | |
19 | ||
20 | .. c:function:: int ioctl( int fd, int request, const struct v4l2_modulator *argp ) | |
21 | ||
22 | Arguments | |
23 | ========= | |
24 | ||
25 | ``fd`` | |
26 | File descriptor returned by :ref:`open() <func-open>`. | |
27 | ||
28 | ``request`` | |
29 | VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR | |
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 | :ref:`v4l2_modulator <v4l2-modulator>` and call the | |
40 | ``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 ``VIDIOC_S_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 | |
af4a4d0d | 60 | :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl is available. |
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61 | |
62 | ||
63 | .. _v4l2-modulator: | |
64 | ||
65 | .. flat-table:: struct v4l2_modulator | |
66 | :header-rows: 0 | |
67 | :stub-columns: 0 | |
68 | :widths: 1 1 2 1 1 | |
69 | ||
70 | ||
71 | - .. row 1 | |
72 | ||
73 | - __u32 | |
74 | ||
75 | - ``index`` | |
76 | ||
77 | - Identifies the modulator, set by the application. | |
78 | ||
79 | - .. row 2 | |
80 | ||
81 | - __u8 | |
82 | ||
83 | - ``name``\ [32] | |
84 | ||
85 | - Name of the modulator, a NUL-terminated ASCII string. This | |
86 | information is intended for the user. | |
87 | ||
88 | - .. row 3 | |
89 | ||
90 | - __u32 | |
91 | ||
92 | - ``capability`` | |
93 | ||
94 | - Modulator capability flags. No flags are defined for this field, | |
95 | the tuner flags in struct :ref:`v4l2_tuner <v4l2-tuner>` are | |
96 | used accordingly. The audio flags indicate the ability to encode | |
97 | audio subprograms. They will *not* change for example with the | |
98 | current video standard. | |
99 | ||
100 | - .. row 4 | |
101 | ||
102 | - __u32 | |
103 | ||
104 | - ``rangelow`` | |
105 | ||
106 | - The lowest tunable frequency in units of 62.5 KHz, or if the | |
107 | ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of | |
108 | 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is | |
109 | set, in units of 1 Hz. | |
110 | ||
111 | - .. row 5 | |
112 | ||
113 | - __u32 | |
114 | ||
115 | - ``rangehigh`` | |
116 | ||
117 | - The highest tunable frequency in units of 62.5 KHz, or if the | |
118 | ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of | |
119 | 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is | |
120 | set, in units of 1 Hz. | |
121 | ||
122 | - .. row 6 | |
123 | ||
124 | - __u32 | |
125 | ||
126 | - ``txsubchans`` | |
127 | ||
128 | - With this field applications can determine how audio sub-carriers | |
129 | shall be modulated. It contains a set of flags as defined in | |
130 | :ref:`modulator-txsubchans`. Note the tuner ``rxsubchans`` flags | |
131 | are reused, but the semantics are different. Video output devices | |
132 | are assumed to have an analog or PCM audio input with 1-3 | |
133 | channels. The ``txsubchans`` flags select one or more channels for | |
134 | modulation, together with some audio subprogram indicator, for | |
135 | example a stereo pilot tone. | |
136 | ||
137 | - .. row 7 | |
138 | ||
139 | - __u32 | |
140 | ||
141 | - ``type`` | |
142 | ||
143 | - :cspan:`2` Type of the modulator, see :ref:`v4l2-tuner-type`. | |
144 | ||
145 | - .. row 8 | |
146 | ||
147 | - __u32 | |
148 | ||
149 | - ``reserved``\ [3] | |
150 | ||
151 | - Reserved for future extensions. Drivers and applications must set | |
152 | the array to zero. | |
153 | ||
154 | ||
155 | ||
156 | .. _modulator-txsubchans: | |
157 | ||
158 | .. flat-table:: Modulator Audio Transmission Flags | |
159 | :header-rows: 0 | |
160 | :stub-columns: 0 | |
161 | :widths: 3 1 4 | |
162 | ||
163 | ||
164 | - .. row 1 | |
165 | ||
166 | - ``V4L2_TUNER_SUB_MONO`` | |
167 | ||
168 | - 0x0001 | |
169 | ||
170 | - Modulate channel 1 as mono audio, when the input has more | |
171 | channels, a down-mix of channel 1 and 2. This flag does not | |
172 | combine with ``V4L2_TUNER_SUB_STEREO`` or | |
173 | ``V4L2_TUNER_SUB_LANG1``. | |
174 | ||
175 | - .. row 2 | |
176 | ||
177 | - ``V4L2_TUNER_SUB_STEREO`` | |
178 | ||
179 | - 0x0002 | |
180 | ||
181 | - Modulate channel 1 and 2 as left and right channel of a stereo | |
182 | audio signal. When the input has only one channel or two channels | |
183 | and ``V4L2_TUNER_SUB_SAP`` is also set, channel 1 is encoded as | |
184 | left and right channel. This flag does not combine with | |
185 | ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_LANG1``. When the | |
186 | driver does not support stereo audio it shall fall back to mono. | |
187 | ||
188 | - .. row 3 | |
189 | ||
190 | - ``V4L2_TUNER_SUB_LANG1`` | |
191 | ||
192 | - 0x0008 | |
193 | ||
194 | - Modulate channel 1 and 2 as primary and secondary language of a | |
195 | bilingual audio signal. When the input has only one channel it is | |
196 | used for both languages. It is not possible to encode the primary | |
197 | or secondary language only. This flag does not combine with | |
198 | ``V4L2_TUNER_SUB_MONO``, ``V4L2_TUNER_SUB_STEREO`` or | |
199 | ``V4L2_TUNER_SUB_SAP``. If the hardware does not support the | |
200 | respective audio matrix, or the current video standard does not | |
201 | permit bilingual audio the ``VIDIOC_S_MODULATOR`` ioctl shall | |
202 | return an EINVAL error code and the driver shall fall back to mono | |
203 | or stereo mode. | |
204 | ||
205 | - .. row 4 | |
206 | ||
207 | - ``V4L2_TUNER_SUB_LANG2`` | |
208 | ||
209 | - 0x0004 | |
210 | ||
211 | - Same effect as ``V4L2_TUNER_SUB_SAP``. | |
212 | ||
213 | - .. row 5 | |
214 | ||
215 | - ``V4L2_TUNER_SUB_SAP`` | |
216 | ||
217 | - 0x0004 | |
218 | ||
219 | - When combined with ``V4L2_TUNER_SUB_MONO`` the first channel is | |
220 | encoded as mono audio, the last channel as Second Audio Program. | |
221 | When the input has only one channel it is used for both audio | |
222 | tracks. When the input has three channels the mono track is a | |
223 | down-mix of channel 1 and 2. When combined with | |
224 | ``V4L2_TUNER_SUB_STEREO`` channel 1 and 2 are encoded as left and | |
225 | right stereo audio, channel 3 as Second Audio Program. When the | |
226 | input has only two channels, the first is encoded as left and | |
227 | right channel and the second as SAP. When the input has only one | |
228 | channel it is used for all audio tracks. It is not possible to | |
229 | encode a Second Audio Program only. This flag must combine with | |
230 | ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the | |
231 | hardware does not support the respective audio matrix, or the | |
232 | current video standard does not permit SAP the | |
233 | ``VIDIOC_S_MODULATOR`` ioctl shall return an EINVAL error code and | |
234 | driver shall fall back to mono or stereo mode. | |
235 | ||
236 | - .. row 6 | |
237 | ||
238 | - ``V4L2_TUNER_SUB_RDS`` | |
239 | ||
240 | - 0x0010 | |
241 | ||
242 | - Enable the RDS encoder for a radio FM transmitter. | |
243 | ||
244 | ||
245 | ||
246 | Return Value | |
247 | ============ | |
248 | ||
249 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
250 | appropriately. The generic error codes are described at the | |
251 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
252 | ||
253 | EINVAL | |
254 | The struct :ref:`v4l2_modulator <v4l2-modulator>` ``index`` is | |
255 | out of bounds. | |
256 | ||
257 | ||
258 | .. ------------------------------------------------------------------------------ | |
259 | .. This file was automatically converted from DocBook-XML with the dbxml | |
260 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes | |
261 | .. from the linux kernel, refer to: | |
262 | .. | |
263 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook | |
264 | .. ------------------------------------------------------------------------------ |