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
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
|
.. -*- coding: utf-8; mode: rst -*-
.. _VIDIOC_G_TUNER:
************************************
ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER
************************************
Name
====
VIDIOC_G_TUNER - VIDIOC_S_TUNER - Get or set tuner attributes
Synopsis
========
.. cpp:function:: int ioctl( int fd, int request, struct v4l2_tuner *argp )
.. cpp:function:: int ioctl( int fd, int request, const struct v4l2_tuner *argp )
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``request``
VIDIOC_G_TUNER, VIDIOC_S_TUNER
``argp``
Description
===========
To query the attributes of a tuner applications initialize the ``index``
field and zero out the ``reserved`` array of a struct
:ref:`v4l2_tuner <v4l2-tuner>` and call the ``VIDIOC_G_TUNER`` ioctl
with a pointer to this structure. Drivers fill the rest of the structure
or return an ``EINVAL`` error code when the index is out of bounds. To
enumerate all tuners applications shall begin at index zero,
incrementing by one until the driver returns ``EINVAL``.
Tuners have two writable properties, the audio mode and the radio
frequency. To change the audio mode, applications initialize the
``index``, ``audmode`` and ``reserved`` fields and call the
``VIDIOC_S_TUNER`` ioctl. This will *not* change the current tuner,
which is determined by the current video input. Drivers may choose a
different audio mode if the requested mode is invalid or unsupported.
Since this is a write-only ioctl, it does not return the actually
selected audio mode.
:ref:`SDR <sdr>` specific tuner types are ``V4L2_TUNER_SDR`` and
``V4L2_TUNER_RF``. For SDR devices ``audmode`` field must be initialized
to zero. The term 'tuner' means SDR receiver in this context.
To change the radio frequency the
:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl is available.
.. _v4l2-tuner:
.. flat-table:: struct v4l2_tuner
:header-rows: 0
:stub-columns: 0
- .. row 1
- __u32
- ``index``
- :cspan:`1` Identifies the tuner, set by the application.
- .. row 2
- __u8
- ``name``\ [32]
- :cspan:`1`
Name of the tuner, a NUL-terminated ASCII string. This information
is intended for the user.
- .. row 3
- __u32
- ``type``
- :cspan:`1` Type of the tuner, see :ref:`v4l2-tuner-type`.
- .. row 4
- __u32
- ``capability``
- :cspan:`1`
Tuner capability flags, see :ref:`tuner-capability`. Audio flags
indicate the ability to decode audio subprograms. They will *not*
change, for example with the current video standard.
When the structure refers to a radio tuner the
``V4L2_TUNER_CAP_LANG1``, ``V4L2_TUNER_CAP_LANG2`` and
``V4L2_TUNER_CAP_NORM`` flags can't be used.
If multiple frequency bands are supported, then ``capability`` is
the union of all ``capability`` fields of each struct
:ref:`v4l2_frequency_band <v4l2-frequency-band>`.
- .. row 5
- __u32
- ``rangelow``
- :cspan:`1` The lowest tunable frequency in units of 62.5 kHz, or
if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units
of 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ``
is set, in units of 1 Hz. If multiple frequency bands are
supported, then ``rangelow`` is the lowest frequency of all the
frequency bands.
- .. row 6
- __u32
- ``rangehigh``
- :cspan:`1` The highest tunable frequency in units of 62.5 kHz,
or if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in
units of 62.5 Hz, or if the ``capability`` flag
``V4L2_TUNER_CAP_1HZ`` is set, in units of 1 Hz. If multiple
frequency bands are supported, then ``rangehigh`` is the highest
frequency of all the frequency bands.
- .. row 7
- __u32
- ``rxsubchans``
- :cspan:`1`
Some tuners or audio decoders can determine the received audio
subprograms by analyzing audio carriers, pilot tones or other
indicators. To pass this information drivers set flags defined in
:ref:`tuner-rxsubchans` in this field. For example:
- .. row 8
-
-
- ``V4L2_TUNER_SUB_MONO``
- receiving mono audio
- .. row 9
-
-
- ``STEREO | SAP``
- receiving stereo audio and a secondary audio program
- .. row 10
-
-
- ``MONO | STEREO``
- receiving mono or stereo audio, the hardware cannot distinguish
- .. row 11
-
-
- ``LANG1 | LANG2``
- receiving bilingual audio
- .. row 12
-
-
- ``MONO | STEREO | LANG1 | LANG2``
- receiving mono, stereo or bilingual audio
- .. row 13
-
-
- :cspan:`1`
When the ``V4L2_TUNER_CAP_STEREO``, ``_LANG1``, ``_LANG2`` or
``_SAP`` flag is cleared in the ``capability`` field, the
corresponding ``V4L2_TUNER_SUB_`` flag must not be set here.
This field is valid only if this is the tuner of the current video
input, or when the structure refers to a radio tuner.
- .. row 14
- __u32
- ``audmode``
- :cspan:`1`
The selected audio mode, see :ref:`tuner-audmode` for valid
values. The audio mode does not affect audio subprogram detection,
and like a :ref:`control` it does not automatically
change unless the requested mode is invalid or unsupported. See
:ref:`tuner-matrix` for possible results when the selected and
received audio programs do not match.
Currently this is the only field of struct
:ref:`struct v4l2_tuner <v4l2-tuner>` applications can change.
- .. row 15
- __u32
- ``signal``
- :cspan:`1` The signal strength if known, ranging from 0 to
65535. Higher values indicate a better signal.
- .. row 16
- __s32
- ``afc``
- :cspan:`1` Automatic frequency control: When the ``afc`` value
is negative, the frequency is too low, when positive too high.
- .. row 17
- __u32
- ``reserved``\ [4]
- :cspan:`1` Reserved for future extensions. Drivers and
applications must set the array to zero.
.. _v4l2-tuner-type:
.. flat-table:: enum v4l2_tuner_type
:header-rows: 0
:stub-columns: 0
:widths: 3 1 4
- .. row 1
- ``V4L2_TUNER_RADIO``
- 1
-
- .. row 2
- ``V4L2_TUNER_ANALOG_TV``
- 2
-
- .. row 3
- ``V4L2_TUNER_SDR``
- 4
-
- .. row 4
- ``V4L2_TUNER_RF``
- 5
-
.. _tuner-capability:
.. flat-table:: Tuner and Modulator Capability Flags
:header-rows: 0
:stub-columns: 0
:widths: 3 1 4
- .. row 1
- ``V4L2_TUNER_CAP_LOW``
- 0x0001
- When set, tuning frequencies are expressed in units of 62.5 Hz
instead of 62.5 kHz.
- .. row 2
- ``V4L2_TUNER_CAP_NORM``
- 0x0002
- This is a multi-standard tuner; the video standard can or must be
switched. (B/G PAL tuners for example are typically not considered
multi-standard because the video standard is automatically
determined from the frequency band.) The set of supported video
standards is available from the struct
:ref:`v4l2_input <v4l2-input>` pointing to this tuner, see the
description of ioctl :ref:`VIDIOC_ENUMINPUT`
for details. Only ``V4L2_TUNER_ANALOG_TV`` tuners can have this
capability.
- .. row 3
- ``V4L2_TUNER_CAP_HWSEEK_BOUNDED``
- 0x0004
- If set, then this tuner supports the hardware seek functionality
where the seek stops when it reaches the end of the frequency
range.
- .. row 4
- ``V4L2_TUNER_CAP_HWSEEK_WRAP``
- 0x0008
- If set, then this tuner supports the hardware seek functionality
where the seek wraps around when it reaches the end of the
frequency range.
- .. row 5
- ``V4L2_TUNER_CAP_STEREO``
- 0x0010
- Stereo audio reception is supported.
- .. row 6
- ``V4L2_TUNER_CAP_LANG1``
- 0x0040
- Reception of the primary language of a bilingual audio program is
supported. Bilingual audio is a feature of two-channel systems,
transmitting the primary language monaural on the main audio
carrier and a secondary language monaural on a second carrier.
Only ``V4L2_TUNER_ANALOG_TV`` tuners can have this capability.
- .. row 7
- ``V4L2_TUNER_CAP_LANG2``
- 0x0020
- Reception of the secondary language of a bilingual audio program
is supported. Only ``V4L2_TUNER_ANALOG_TV`` tuners can have this
capability.
- .. row 8
- ``V4L2_TUNER_CAP_SAP``
- 0x0020
- Reception of a secondary audio program is supported. This is a
feature of the BTSC system which accompanies the NTSC video
standard. Two audio carriers are available for mono or stereo
transmissions of a primary language, and an independent third
carrier for a monaural secondary language. Only
``V4L2_TUNER_ANALOG_TV`` tuners can have this capability.
.. note::
The ``V4L2_TUNER_CAP_LANG2`` and ``V4L2_TUNER_CAP_SAP``
flags are synonyms. ``V4L2_TUNER_CAP_SAP`` applies when the tuner
supports the ``V4L2_STD_NTSC_M`` video standard.
- .. row 9
- ``V4L2_TUNER_CAP_RDS``
- 0x0080
- RDS capture is supported. This capability is only valid for radio
tuners.
- .. row 10
- ``V4L2_TUNER_CAP_RDS_BLOCK_IO``
- 0x0100
- The RDS data is passed as unparsed RDS blocks.
- .. row 11
- ``V4L2_TUNER_CAP_RDS_CONTROLS``
- 0x0200
- The RDS data is parsed by the hardware and set via controls.
- .. row 12
- ``V4L2_TUNER_CAP_FREQ_BANDS``
- 0x0400
- The :ref:`VIDIOC_ENUM_FREQ_BANDS`
ioctl can be used to enumerate the available frequency bands.
- .. row 13
- ``V4L2_TUNER_CAP_HWSEEK_PROG_LIM``
- 0x0800
- The range to search when using the hardware seek functionality is
programmable, see
:ref:`VIDIOC_S_HW_FREQ_SEEK` for
details.
- .. row 14
- ``V4L2_TUNER_CAP_1HZ``
- 0x1000
- When set, tuning frequencies are expressed in units of 1 Hz
instead of 62.5 kHz.
.. _tuner-rxsubchans:
.. flat-table:: Tuner Audio Reception Flags
:header-rows: 0
:stub-columns: 0
:widths: 3 1 4
- .. row 1
- ``V4L2_TUNER_SUB_MONO``
- 0x0001
- The tuner receives a mono audio signal.
- .. row 2
- ``V4L2_TUNER_SUB_STEREO``
- 0x0002
- The tuner receives a stereo audio signal.
- .. row 3
- ``V4L2_TUNER_SUB_LANG1``
- 0x0008
- The tuner receives the primary language of a bilingual audio
signal. Drivers must clear this flag when the current video
standard is ``V4L2_STD_NTSC_M``.
- .. row 4
- ``V4L2_TUNER_SUB_LANG2``
- 0x0004
- The tuner receives the secondary language of a bilingual audio
signal (or a second audio program).
- .. row 5
- ``V4L2_TUNER_SUB_SAP``
- 0x0004
- The tuner receives a Second Audio Program.
.. note::
The ``V4L2_TUNER_SUB_LANG2`` and ``V4L2_TUNER_SUB_SAP``
flags are synonyms. The ``V4L2_TUNER_SUB_SAP`` flag applies
when the current video standard is ``V4L2_STD_NTSC_M``.
- .. row 6
- ``V4L2_TUNER_SUB_RDS``
- 0x0010
- The tuner receives an RDS channel.
.. _tuner-audmode:
.. flat-table:: Tuner Audio Modes
:header-rows: 0
:stub-columns: 0
:widths: 3 1 4
- .. row 1
- ``V4L2_TUNER_MODE_MONO``
- 0
- Play mono audio. When the tuner receives a stereo signal this a
down-mix of the left and right channel. When the tuner receives a
bilingual or SAP signal this mode selects the primary language.
- .. row 2
- ``V4L2_TUNER_MODE_STEREO``
- 1
- Play stereo audio. When the tuner receives bilingual audio it may
play different languages on the left and right channel or the
primary language is played on both channels.
Playing different languages in this mode is deprecated. New
drivers should do this only in ``MODE_LANG1_LANG2``.
When the tuner receives no stereo signal or does not support
stereo reception the driver shall fall back to ``MODE_MONO``.
- .. row 3
- ``V4L2_TUNER_MODE_LANG1``
- 3
- Play the primary language, mono or stereo. Only
``V4L2_TUNER_ANALOG_TV`` tuners support this mode.
- .. row 4
- ``V4L2_TUNER_MODE_LANG2``
- 2
- Play the secondary language, mono. When the tuner receives no
bilingual audio or SAP, or their reception is not supported the
driver shall fall back to mono or stereo mode. Only
``V4L2_TUNER_ANALOG_TV`` tuners support this mode.
- .. row 5
- ``V4L2_TUNER_MODE_SAP``
- 2
- Play the Second Audio Program. When the tuner receives no
bilingual audio or SAP, or their reception is not supported the
driver shall fall back to mono or stereo mode. Only
``V4L2_TUNER_ANALOG_TV`` tuners support this mode.
.. note:: The ``V4L2_TUNER_MODE_LANG2`` and ``V4L2_TUNER_MODE_SAP``
are synonyms.
- .. row 6
- ``V4L2_TUNER_MODE_LANG1_LANG2``
- 4
- Play the primary language on the left channel, the secondary
language on the right channel. When the tuner receives no
bilingual audio or SAP, it shall fall back to ``MODE_LANG1`` or
``MODE_MONO``. Only ``V4L2_TUNER_ANALOG_TV`` tuners support this
mode.
.. _tuner-matrix:
.. flat-table:: Tuner Audio Matrix
:header-rows: 2
:stub-columns: 0
- .. row 1
-
- :cspan:`5` Selected ``V4L2_TUNER_MODE_``
- .. row 2
- Received ``V4L2_TUNER_SUB_``
- ``MONO``
- ``STEREO``
- ``LANG1``
- ``LANG2 = SAP``
- ``LANG1_LANG2``\ [#f1]_
- .. row 3
- ``MONO``
- Mono
- Mono/Mono
- Mono
- Mono
- Mono/Mono
- .. row 4
- ``MONO | SAP``
- Mono
- Mono/Mono
- Mono
- SAP
- Mono/SAP (preferred) or Mono/Mono
- .. row 5
- ``STEREO``
- L+R
- L/R
- Stereo L/R (preferred) or Mono L+R
- Stereo L/R (preferred) or Mono L+R
- L/R (preferred) or L+R/L+R
- .. row 6
- ``STEREO | SAP``
- L+R
- L/R
- Stereo L/R (preferred) or Mono L+R
- SAP
- L+R/SAP (preferred) or L/R or L+R/L+R
- .. row 7
- ``LANG1 | LANG2``
- Language 1
- Lang1/Lang2 (deprecated [#f2]_) or Lang1/Lang1
- Language 1
- Language 2
- Lang1/Lang2 (preferred) or Lang1/Lang1
Return Value
============
On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
EINVAL
The struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` is out of
bounds.
.. [#f1]
This mode has been added in Linux 2.6.17 and may not be supported by
older drivers.
.. [#f2]
Playback of both languages in ``MODE_STEREO`` is deprecated. In the
future drivers should produce only the primary language in this mode.
Applications should request ``MODE_LANG1_LANG2`` to record both
languages or a stereo signal.
|