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1 .\" $NetBSD: audio.4,v 1.69 2009/01/03 17:44:20 christos Exp $
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30 .Dd September 29, 2009
31 .Dt AUDIO 4
32 .Os
33 .Sh NAME
34 .Nm audio
35 .Nd device-independent audio driver layer
36 .Sh SYNOPSIS
37 .In sys/audioio.h
38 .Sh DESCRIPTION
39 The
40 .Nm
41 driver provides support for various audio peripherals.
42 It provides a uniform programming interface layer above different
43 underlying audio hardware drivers.
44 The audio layer provides full-duplex operation if the
45 underlying hardware configuration supports it.
46 .Pp
47 There are four device files available for audio operation:
48 .Pa /dev/audio ,
49 .Pa /dev/sound ,
50 .Pa /dev/audioctl ,
51 and
52 .Pa /dev/mixer .
53 .Pp
54 .Pa /dev/audio
55 and
56 .Pa /dev/sound
57 are used for recording or playback of digital samples.
58 .Pp
59 .Pa /dev/mixer
60 is used to manipulate volume, recording source, or other audio mixer
61 functions.
62 .Pp
63 .Pa /dev/audioctl
64 accepts the same
65 .Xr ioctl 2
66 operations as
67 .Pa /dev/sound ,
68 but no other operations.
69 .Pp
70 In contrast to
71 .Pa /dev/sound
72 which has the exclusive open property
73 .Pa /dev/audioctl
74 can be opened at any time and can be used to manipulate the audio device
75 while it is in use.
76 .Sh SAMPLING DEVICES
77 When
78 .Pa /dev/audio
79 is opened, it automatically directs the underlying driver to manipulate
80 monaural 8-bit mu-law samples.
81 In addition, if it is opened read-only
82 (write-only) the device is set to half-duplex record (play) mode with
83 recording (playing) unpaused and playing (recording) paused.
84 When
85 .Pa /dev/sound
86 is opened, it maintains the previous audio sample mode and
87 record/playback mode.
88 In all other respects
89 .Pa /dev/audio
90 and
91 .Pa /dev/sound
92 are identical.
93 .Pp
94 Only one process may hold open a sampling device at a given time
95 (although file descriptors may be shared between processes once the
96 first open completes).
97 .Pp
98 On a half-duplex device, writes while recording is in progress will be
99 immediately discarded.
100 Similarly, reads while playback is in progress
101 will be filled with silence but delayed to return at the current
102 sampling rate.
103 If both playback and recording are requested on a half-duplex
104 device, playback mode takes precedence and recordings will get silence.
105 .Pp
106 On a full-duplex device, reads and writes may operate
107 concurrently without interference.
108 If a full-duplex capable audio device is opened for both reading and writing
109 it will start in half-duplex play mode; full-duplex mode has to be set
110 explicitly.
111 .Pp
112 On either type of device, if the playback mode is paused then silence is
113 played instead of the provided samples, and if recording is paused then
114 the process blocks in
115 .Xr read 2
116 until recording is unpaused.
117 .Pp
118 If a writing process does not call
119 .Xr write 2
120 frequently enough to provide samples at the pace the hardware
121 consumes them silence is inserted.
122 If the
123 .Dv AUMODE_PLAY_ALL
124 mode is not set the writing process must
125 provide enough data via
126 subsequent write calls to
127 .Dq catch up
128 in time to the current audio
129 block before any more process-provided samples will be played.
130 If a reading process does not call
131 .Xr read 2
132 frequently enough, it will simply miss samples.
133 .Pp
134 The audio device is normally accessed with
135 .Xr read 2
136 or
137 .Xr write 2
138 calls, but it can also be mapped into user memory with
139 .Xr mmap 2
140 (when supported by the device).
141 Once the device has been mapped it can no longer be accessed
142 by read or write; all access is by reading and writing to
143 the mapped memory.
144 The device appears as a block of memory
145 of size
146 .Va buffersize
147 (as available via
148 .Dv AUDIO_GETINFO
149 or
150 .Dv AUDIO_GETBUFINFO ) .
151 The device driver will continuously move data from this buffer
152 from/to the audio hardware, wrapping around at the end of the buffer.
153 To find out where the hardware is currently accessing data in the buffer the
154 .Dv AUDIO_GETIOFFS
155 and
156 .Dv AUDIO_GETOOFFS
157 calls can be used.
158 The playing and recording buffers are distinct and must be
159 mapped separately if both are to be used.
160 Only encodings that are not emulated (i.e. where
161 .Dv AUDIO_ENCODINGFLAG_EMULATED
162 is not set) work properly for a mapped device.
163 .Pp
164 The audio device, like most devices, can be used in
165 .Va select ,
166 can be set in non-blocking mode and can be set (with a
167 .Dv FIOASYNC
168 ioctl) to send a
169 .Dv SIGIO
170 when I/O is possible.
171 The mixer device can be set to generate a
172 .Dv SIGIO
173 whenever a mixer value is changed.
174 .Pp
175 The following
176 .Xr ioctl 2
177 commands are supported on the sample devices:
178 .Pp
179 .Bl -tag -width indent
180 .It Dv AUDIO_FLUSH
181 This command stops all playback and recording, clears all queued
182 buffers, resets error counters, and restarts recording and playback as
183 appropriate for the current sampling mode.
184 .It Dv AUDIO_RERROR (int)
185 This command fetches the count of dropped input samples into its integer
186 argument.
187 There is no information regarding when in the sample stream
188 they were dropped.
189 .It Dv AUDIO_WSEEK (int)
190 This command fetches the count of samples that are queued ahead of the
191 first sample in the most recent sample block written into its integer argument.
192 .It Dv AUDIO_DRAIN
193 This command suspends the calling process until all queued playback
194 samples have been played by the hardware.
195 .It Dv AUDIO_GETDEV (audio_device_t)
196 This command fetches the current hardware device information into the
197 audio_device_t argument.
198 .Bd -literal
199 typedef struct audio_device {
200 char name[MAX_AUDIO_DEV_LEN];
201 char version[MAX_AUDIO_DEV_LEN];
202 char config[MAX_AUDIO_DEV_LEN];
203 } audio_device_t;
204 .Ed
205 .It Dv AUDIO_GETFD (int)
206 The command returns the current setting of the full duplex mode.
207 .It Dv AUDIO_GETENC (audio_encoding_t)
208 This command is used iteratively to fetch sample encoding names and
209 format_ids into the input/output audio_encoding_t argument.
210 .Bd -literal
211 typedef struct audio_encoding {
212 int index; /* input: nth encoding */
213 char name[MAX_AUDIO_DEV_LEN]; /* name of encoding */
214 int encoding; /* value for encoding parameter */
215 int precision; /* value for precision parameter */
216 int flags;
217 #define AUDIO_ENCODINGFLAG_EMULATED 1 /* software emulation mode */
218 } audio_encoding_t;
219 .Ed
220 .Pp
221 To query
222 all the supported encodings, start with an index field of 0 and
223 continue with successive encodings (1, 2, ...) until the command returns
224 an error.
225 .It Dv AUDIO_SETFD (int)
226 This command sets the device into full-duplex operation if its integer
227 argument has a non-zero value, or into half-duplex operation if it
228 contains a zero value.
229 If the device does not support full-duplex
230 operation, attempting to set full-duplex mode returns an error.
231 .It Dv AUDIO_GETPROPS (int)
232 This command gets a bit set of hardware properties.
233 If the hardware
234 has a certain property the corresponding bit is set, otherwise it is not.
235 The properties can have the following values:
236 .Pp
237 .Bl -tag -width AUDIO_PROP_INDEPENDENT -compact
238 .It Dv AUDIO_PROP_FULLDUPLEX
239 the device admits full duplex operation.
240 .It Dv AUDIO_PROP_MMAP
241 the device can be used with
242 .Xr mmap 2 .
243 .It Dv AUDIO_PROP_INDEPENDENT
244 the device can set the playing and recording encoding parameters
245 independently.
246 .It Dv AUDIO_PROP_PLAYBACK
247 the device is capable of audio playback.
248 .It Dv AUDIO_PROP_CAPTURE
249 the device is capable of audio capture.
250 .El
251 .It Dv AUDIO_GETIOFFS (audio_offset_t)
252 .It Dv AUDIO_GETOOFFS (audio_offset_t)
253 This command fetches the current offset in the input(output) buffer where
254 the audio hardware's DMA engine will be putting(getting) data.
255 It mostly useful when the device
256 buffer is available in user space via the
257 .Xr mmap 2
258 call.
259 The information is returned in the audio_offset structure.
260 .Bd -literal
261 typedef struct audio_offset {
262 u_int samples; /* Total number of bytes transferred */
263 u_int deltablks; /* Blocks transferred since last checked */
264 u_int offset; /* Physical transfer offset in buffer */
265 } audio_offset_t;
266 .Ed
267 .It Dv AUDIO_GETINFO (audio_info_t)
268 .It Dv AUDIO_GETBUFINFO (audio_info_t)
269 .It Dv AUDIO_SETINFO (audio_info_t)
270 Get or set audio information as encoded in the audio_info structure.
271 .Bd -literal
272 typedef struct audio_info {
273 struct audio_prinfo play; /* info for play (output) side */
274 struct audio_prinfo record; /* info for record (input) side */
275 u_int monitor_gain; /* input to output mix */
276 /* BSD extensions */
277 u_int blocksize; /* H/W read/write block size */
278 u_int hiwat; /* output high water mark */
279 u_int lowat; /* output low water mark */
280 u_int _ispare1;
281 u_int mode; /* current device mode */
282 #define AUMODE_PLAY 0x01
283 #define AUMODE_RECORD 0x02
284 #define AUMODE_PLAY_ALL 0x04 /* do not do real-time correction */
285 } audio_info_t;
286 .Ed
287 .Pp
288 When setting the current state with
289 .Dv AUDIO_SETINFO ,
290 the audio_info structure should first be initialized with
291 .Dv AUDIO_INITINFO Po \*[Am]info Pc
292 and then the particular values to be changed should be set.
293 This allows the audio driver to only set those things that you wish
294 to change and eliminates the need to query the device with
295 .Dv AUDIO_GETINFO
296 or
297 .Dv AUDIO_GETBUFINFO
298 first.
299 .Pp
300 The
301 .Va mode
302 field should be set to
303 .Dv AUMODE_PLAY ,
304 .Dv AUMODE_RECORD ,
305 .Dv AUMODE_PLAY_ALL ,
306 or a bitwise OR combination of the three.
307 Only full-duplex audio devices support
308 simultaneous record and playback.
309 .Pp
310 .Va hiwat
311 and
312 .Va lowat
313 are used to control write behavior.
314 Writes to the audio devices will queue up blocks until the high-water
315 mark is reached, at which point any more write calls will block
316 until the queue is drained to the low-water mark.
317 .Va hiwat
318 and
319 .Va lowat
320 set those high- and low-water marks (in audio blocks).
321 The default for
322 .Va hiwat
323 is the maximum value and for
324 .Va lowat
325 75 % of
326 .Va hiwat .
327 .Pp
328 .Va blocksize
329 sets the current audio blocksize.
330 The generic audio driver layer and the hardware driver have the
331 opportunity to adjust this block size to get it within
332 implementation-required limits.
333 Upon return from an
334 .Dv AUDIO_SETINFO
335 call, the actual blocksize set is returned in this field.
336 Normally the
337 .Va blocksize
338 is calculated to correspond to 50ms of sound and it is recalculated
339 when the encoding parameter changes, but if the
340 .Va blocksize
341 is set explicitly this value becomes sticky, i.e., it remains
342 even when the encoding is changed.
343 The stickiness can be cleared by reopening the device or setting the
344 .Va blocksize
345 to 0.
346 .Bd -literal
347 struct audio_prinfo {
348 u_int sample_rate; /* sample rate in samples/s */
349 u_int channels; /* number of channels, usually 1 or 2 */
350 u_int precision; /* number of bits/sample */
351 u_int encoding; /* data encoding (AUDIO_ENCODING_* below) */
352 u_int gain; /* volume level */
353 u_int port; /* selected I/O port */
354 u_long seek; /* BSD extension */
355 u_int avail_ports; /* available I/O ports */
356 u_int buffer_size; /* total size audio buffer */
357 u_int _ispare[1];
358 /* Current state of device: */
359 u_int samples; /* number of samples */
360 u_int eof; /* End Of File (zero-size writes) counter */
361 u_char pause; /* non-zero if paused, zero to resume */
362 u_char error; /* non-zero if underflow/overflow occurred */
363 u_char waiting; /* non-zero if another process hangs in open */
364 u_char balance; /* stereo channel balance */
365 u_char cspare[2];
366 u_char open; /* non-zero if currently open */
367 u_char active; /* non-zero if I/O is currently active */
368 };
369 .Ed
370 .Pp
371 Note: many hardware audio drivers require identical playback and
372 recording sample rates, sample encodings, and channel counts.
373 The playing information is always set last and will prevail on such hardware.
374 If the hardware can handle different settings the
375 .Dv AUDIO_PROP_INDEPENDENT
376 property is set.
377 .Pp
378 The encoding parameter can have the following values:
379 .Pp
380 .Bl -tag -width AUDIO_ENCODING_SLINEAR_BE -compact
381 .It Dv AUDIO_ENCODING_ULAW
382 mu-law encoding, 8 bits/sample
383 .It Dv AUDIO_ENCODING_ALAW
384 A-law encoding, 8 bits/sample
385 .It Dv AUDIO_ENCODING_SLINEAR
386 two's complement signed linear encoding with the platform byte order
387 .It Dv AUDIO_ENCODING_ULINEAR
388 unsigned linear encoding with the platform byte order
389 .It Dv AUDIO_ENCODING_ADPCM
390 ADPCM encoding, 8 bits/sample
391 .It Dv AUDIO_ENCODING_SLINEAR_LE
392 two's complement signed linear encoding with little endian byte order
393 .It Dv AUDIO_ENCODING_SLINEAR_BE
394 two's complement signed linear encoding with big endian byte order
395 .It Dv AUDIO_ENCODING_ULINEAR_LE
396 unsigned linear encoding with little endian byte order
397 .It Dv AUDIO_ENCODING_ULINEAR_BE
398 unsigned linear encoding with big endian byte order
399 .El
400 .Pp
401 The
402 .Va gain ,
403 .Va port
404 and
405 .Va balance
406 settings provide simple shortcuts to the richer mixer
407 interface described below and are not obtained by
408 .Dv AUDIO_GETBUFINFO .
409 The gain should be in the range
410 .Bq Dv AUDIO_MIN_GAIN , Dv AUDIO_MAX_GAIN
411 and the balance in the range
412 .Bq Dv AUDIO_LEFT_BALANCE , Dv AUDIO_RIGHT_BALANCE
413 with the normal setting at
414 .Dv AUDIO_MID_BALANCE .
415 .Pp
416 The input port should be a combination of:
417 .Pp
418 .Bl -tag -width AUDIO_MICROPHONE -compact
419 .It Dv AUDIO_MICROPHONE
420 to select microphone input.
421 .It Dv AUDIO_LINE_IN
422 to select line input.
423 .It Dv AUDIO_CD
424 to select CD input.
425 .El
426 .Pp
427 The output port should be a combination of:
428 .Pp
429 .Bl -tag -width AUDIO_HEADPHONE -compact
430 .It Dv AUDIO_SPEAKER
431 to select speaker output.
432 .It Dv AUDIO_HEADPHONE
433 to select headphone output.
434 .It Dv AUDIO_LINE_OUT
435 to select line output.
436 .El
437 .Pp
438 The available ports can be found in
439 .Va avail_ports
440 .Dv ( AUDIO_GETBUFINFO
441 only).
442 .Pp
443 .Va buffer_size
444 is the total size of the audio buffer.
445 The buffer size divided by the
446 .Va blocksize
447 gives the maximum value for
448 .Va hiwat .
449 Currently the
450 .Va buffer_size
451 can only be read and not set.
452 .Pp
453 The
454 .Va seek
455 and
456 .Va samples
457 fields are only used by
458 .Dv AUDIO_GETINFO
459 and
460 .Dv AUDIO_GETBUFINFO .
461 .Va seek
462 represents the count of
463 samples pending;
464 .Va samples
465 represents the total number of bytes recorded or played, less those
466 that were dropped due to inadequate consumption/production rates.
467 .Pp
468 .Va pause
469 returns the current pause/unpause state for recording or playback.
470 For
471 .Dv AUDIO_SETINFO ,
472 if the pause value is specified it will either pause
473 or unpause the particular direction.
474 .El
475 .Sh MIXER DEVICE
476 The mixer device,
477 .Pa /dev/mixer ,
478 may be manipulated with
479 .Xr ioctl 2
480 but does not support
481 .Xr read 2
482 or
483 .Xr write 2 .
484 It supports the following
485 .Xr ioctl 2
486 commands:
487 .Bl -tag -width indent
488 .It Dv AUDIO_GETDEV (audio_device_t)
489 This command is the same as described above for the sampling devices.
490 .It Dv AUDIO_MIXER_READ (mixer_ctrl_t)
491 .It Dv AUDIO_MIXER_WRITE (mixer_ctrl_t)
492 These commands read the current mixer state or set new mixer state for
493 the specified device
494 .Va dev .
495 .Va type
496 identifies which type of value is supplied in the
497 .Va mixer_ctrl_t
498 argument.
499 .Bd -literal
500 #define AUDIO_MIXER_CLASS 0
501 #define AUDIO_MIXER_ENUM 1
502 #define AUDIO_MIXER_SET 2
503 #define AUDIO_MIXER_VALUE 3
504 typedef struct mixer_ctrl {
505 int dev; /* input: nth device */
506 int type;
507 union {
508 int ord; /* enum */
509 int mask; /* set */
510 mixer_level_t value; /* value */
511 } un;
512 } mixer_ctrl_t;
514 #define AUDIO_MIN_GAIN 0
515 #define AUDIO_MAX_GAIN 255
516 typedef struct mixer_level {
517 int num_channels;
518 u_char level[8]; /* [num_channels] */
519 } mixer_level_t;
520 #define AUDIO_MIXER_LEVEL_MONO 0
521 #define AUDIO_MIXER_LEVEL_LEFT 0
522 #define AUDIO_MIXER_LEVEL_RIGHT 1
523 .Ed
524 .Pp
525 For a mixer value, the
526 .Va value
527 field specifies both the number of channels and the values for each
528 channel.
529 If the channel count does not match the current channel count, the
530 attempt to change the setting may fail (depending on the hardware
531 device driver implementation).
532 For an enumeration value, the
533 .Va ord
534 field should be set to one of the possible values as returned by a prior
535 .Dv AUDIO_MIXER_DEVINFO
536 command.
537 The type
538 .Dv AUDIO_MIXER_CLASS
539 is only used for classifying particular mixer device
540 types and is not used for
541 .Dv AUDIO_MIXER_READ
542 or
543 .Dv AUDIO_MIXER_WRITE .
544 .It Dv AUDIO_MIXER_DEVINFO (mixer_devinfo_t)
545 This command is used iteratively to fetch audio mixer device information
546 into the input/output mixer_devinfo_t argument.
547 To query all the supported devices, start with an index field of
548 0 and continue with successive devices (1, 2, ...) until the
549 command returns an error.
550 .Bd -literal
551 typedef struct mixer_devinfo {
552 int index; /* input: nth mixer device */
553 audio_mixer_name_t label;
554 int type;
555 int mixer_class;
556 int next, prev;
557 #define AUDIO_MIXER_LAST -1
558 union {
559 struct audio_mixer_enum {
560 int num_mem;
561 struct {
562 audio_mixer_name_t label;
563 int ord;
564 } member[32];
565 } e;
566 struct audio_mixer_set {
567 int num_mem;
568 struct {
569 audio_mixer_name_t label;
570 int mask;
571 } member[32];
572 } s;
573 struct audio_mixer_value {
574 audio_mixer_name_t units;
575 int num_channels;
576 int delta;
577 } v;
578 } un;
579 } mixer_devinfo_t;
580 .Ed
581 .Pp
582 The
583 .Va label
584 field identifies the name of this particular mixer control.
585 The
586 .Va index
587 field may be used as the
588 .Va dev
589 field in
590 .Dv AUDIO_MIXER_READ
591 and
592 .Dv AUDIO_MIXER_WRITE
593 commands.
594 The
595 .Va type
596 field identifies the type of this mixer control.
597 Enumeration types are typically used for on/off style controls (e.g. a
598 mute control) or for input/output device selection (e.g. select
599 recording input source from CD, line in, or microphone).
600 Set types are similar to enumeration types but any combination
601 of the mask bits can be used.
602 .Pp
603 The
604 .Va mixer_class
605 field identifies what class of control this is.
606 The
607 .Pq arbitrary
608 value set by the hardware driver may be determined by examining the
609 .Va mixer_class
610 field of the class itself,
611 a mixer of type
612 .Dv AUDIO_MIXER_CLASS .
613 For example, a mixer controlling the input gain on the line in circuit
614 would have a
615 .Va mixer_class
616 that matches an input class device with the name
617 .Dq inputs
618 .Dv ( AudioCinputs ) ,
619 and would have a
620 .Va label
621 of
622 .Dq line
623 .Dv ( AudioNline ) .
624 Mixer controls which control audio circuitry for a particular audio
625 source (e.g. line-in, CD in, DAC output) are collected under the input class,
626 while those which control all audio sources (e.g. master volume,
627 equalization controls) are under the output class.
628 Hardware devices capable of recording typically also have a record class,
629 for controls that only affect recording,
630 and also a monitor class.
631 .Pp
632 The
633 .Va next
634 and
635 .Va prev
636 may be used by the hardware device driver to provide hints for the next
637 and previous devices in a related set (for example, the line in level
638 control would have the line in mute as its
639 .Dq next
640 value).
641 If there is no relevant next or previous value,
642 .Dv AUDIO_MIXER_LAST
643 is specified.
644 .Pp
645 For
646 .Dv AUDIO_MIXER_ENUM
647 mixer control types,
648 the enumeration values and their corresponding names are filled in.
649 For example, a mute control would return appropriate values paired with
650 .Dv AudioNon
651 and
652 .Dv AudioNoff .
653 For
654 .Dv AUDIO_MIXER_VALUE
655 and
656 .Dv AUDIO_MIXER_SET
657 mixer control types, the channel count is
658 returned; the units name specifies what the level controls (typical
659 values are
660 .Dv AudioNvolume ,
661 .Dv AudioNtreble ,
662 .Dv AudioNbass ) .
663 .\" For AUDIO_MIXER_SET mixer control types, what is what?
664 .El
665 .Pp
666 By convention, all the mixer devices can be distinguished from other
667 mixer controls because they use a name from one of the
668 .Dv AudioC*
669 string values.
670 .Sh FILES
671 .Bl -tag -width /dev/audioctl -compact
672 .It Pa /dev/audio
673 .It Pa /dev/audioctl
674 .It Pa /dev/sound
675 .It Pa /dev/mixer
676 .El
677 .Sh SEE ALSO
678 .Xr audioctl 1 ,
679 .Xr mixerctl 1 ,
680 .Xr ioctl 2 ,
681 .Xr ossaudio 3 ,
682 .Xr midi 4 ,
683 .Xr radio 4
684 .Ss ISA bus
685 .Xr aria 4 ,
686 .Xr ess 4 ,
687 .Xr gus 4 ,
688 .Xr guspnp 4 ,
689 .Xr pas 4 ,
690 .Xr sb 4 ,
691 .Xr wss 4 ,
692 .Xr ym 4
693 .Ss PCI bus
694 .Xr auacer 4 ,
695 .Xr auich 4 ,
696 .Xr auixp 4 ,
697 .Xr autri 4 ,
698 .Xr auvia 4 ,
699 .Xr azalia 4 ,
700 .Xr clcs 4 ,
701 .Xr clct 4 ,
702 .Xr cmpci 4 ,
703 .Xr eap 4 ,
704 .Xr emuxki 4 ,
705 .Xr esa 4 ,
706 .Xr esm 4 ,
707 .Xr eso 4 ,
708 .Xr fms 4 ,
709 .Xr neo 4 ,
710 .Xr sv 4 ,
711 .Xr yds 4
712 .Ss TURBOchannel
713 .Xr bba 4
714 .Ss USB
715 .Xr uaudio 4
716 .Sh BUGS
717 If the device is used in
718 .Xr mmap 2
719 it is currently always mapped for writing (playing) due to
720 VM system weirdness.