Annotation of src/usr.bin/aucat/aucat.1, Revision 1.77
1.77 ! jmc 1: .\" $OpenBSD: aucat.1,v 1.76 2011/04/28 06:19:57 ratchov Exp $
1.1 kstailey 2: .\"
1.16 ratchov 3: .\" Copyright (c) 2006 Alexandre Ratchov <alex@caoua.org>
1.1 kstailey 4: .\"
1.16 ratchov 5: .\" Permission to use, copy, modify, and distribute this software for any
6: .\" purpose with or without fee is hereby granted, provided that the above
7: .\" copyright notice and this permission notice appear in all copies.
1.1 kstailey 8: .\"
1.16 ratchov 9: .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10: .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11: .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12: .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13: .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14: .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15: .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1.1 kstailey 16: .\"
1.77 ! jmc 17: .Dd $Mdocdate: April 28 2011 $
1.1 kstailey 18: .Dt AUCAT 1
1.5 aaron 19: .Os
1.1 kstailey 20: .Sh NAME
21: .Nm aucat
1.47 ratchov 22: .Nd audio server and stream manipulation tool
1.1 kstailey 23: .Sh SYNOPSIS
24: .Nm aucat
1.16 ratchov 25: .Bk -words
1.59 ratchov 26: .Op Fl dlnu
1.70 ratchov 27: .Op Fl a Ar flag
1.49 jmc 28: .Op Fl b Ar nframes
1.16 ratchov 29: .Op Fl C Ar min : Ns Ar max
30: .Op Fl c Ar min : Ns Ar max
31: .Op Fl e Ar enc
1.9 millert 32: .Op Fl f Ar device
1.16 ratchov 33: .Op Fl h Ar fmt
34: .Op Fl i Ar file
1.68 ratchov 35: .Op Fl j Ar flag
1.76 ratchov 36: .Op Fl L Ar addr
1.37 ratchov 37: .Op Fl m Ar mode
1.16 ratchov 38: .Op Fl o Ar file
1.66 ratchov 39: .Op Fl q Ar device
1.16 ratchov 40: .Op Fl r Ar rate
1.57 ratchov 41: .Op Fl s Ar name
1.62 ratchov 42: .Op Fl t Ar mode
1.54 ratchov 43: .Op Fl U Ar unit
1.30 ratchov 44: .Op Fl v Ar volume
1.22 ratchov 45: .Op Fl x Ar policy
1.62 ratchov 46: .Op Fl z Ar nframes
1.16 ratchov 47: .Ek
1.1 kstailey 48: .Sh DESCRIPTION
1.9 millert 49: .Nm
1.71 ratchov 50: is an audio utility which can simultaneously play and record
51: any number of audio
52: .Em streams
53: on any number of audio devices,
54: possibly controlled through MIDI.
55: It can also act as an audio server, in which case streams
56: correspond to client connections rather than plain files.
57: .Pp
58: Audio devices are independent.
59: A list of streams is attached to each audio device,
60: as well as an optional list of MIDI ports to control the device.
61: A typical invocation of
62: .Nm
63: consists in providing streams to play and record,
64: and possibly the audio device to use, if the default is not desired.
65: .Pp
66: This also applies to server mode, except that streams are created
67: dynamically when clients connect to the server.
68: Thus, instead of actual streams (paths to plain files),
69: templates for client streams (sub-device names) must be provided.
1.17 jmc 70: .Pp
1.16 ratchov 71: The options are as follows:
1.26 ratchov 72: .Bl -tag -width Ds
1.70 ratchov 73: .It Fl a Ar flag
74: Control whether
75: .Nm
1.71 ratchov 76: opens the audio device only when needed or keeps it open all the time.
1.70 ratchov 77: If the flag is
78: .Va on
79: then the device is kept open all the time, ensuring no other program can
80: steal it.
81: If the flag is
82: .Va off ,
83: then it's automatically closed, allowing other programs to have direct
84: access to the device, or the device to be disconnected.
85: The default is
86: .Va on .
1.49 jmc 87: .It Fl b Ar nframes
1.66 ratchov 88: The buffer size of the audio device in frames.
1.49 jmc 89: A frame consists of one sample for each channel in the stream.
90: This is the number of frames that will be buffered before being played
91: and thus controls the playback latency.
1.25 jmc 92: .It Xo
93: .Fl C Ar min : Ns Ar max ,
94: .Fl c Ar min : Ns Ar max
95: .Xc
1.72 jmc 96: The range of stream channel numbers for recording and playback directions,
97: respectively.
1.17 jmc 98: The default is 0:1, i.e. stereo.
1.59 ratchov 99: .It Fl d
1.71 ratchov 100: Increase log verbosity.
1.59 ratchov 101: .Nm
1.75 okan 102: logs on
103: .Em stderr
104: until it daemonizes.
1.26 ratchov 105: .It Fl e Ar enc
106: Encoding of the playback or recording stream (see below).
1.17 jmc 107: The default is signed, 16-bit, native byte order.
108: .It Fl f Ar device
1.71 ratchov 109: Add this
1.57 ratchov 110: .Xr sndio 7
1.71 ratchov 111: audio device to devices used for playing and/or recording.
112: Preceding streams
113: .Pq Fl ios ,
114: control MIDI ports
115: .Pq Fl q ,
116: and per-device options
117: .Pq Fl abz
118: apply to this device.
119: Device mode and parameters are determined from streams
120: attached to it.
1.26 ratchov 121: .It Fl h Ar fmt
122: File format of the playback or record stream (see below).
1.17 jmc 123: The default is auto.
1.16 ratchov 124: .It Fl i Ar file
1.71 ratchov 125: Add this file to the list of streams to play.
1.16 ratchov 126: If the option argument is
127: .Sq -
128: then standard input will be used.
1.68 ratchov 129: .It Fl j Ar flag
1.71 ratchov 130: Control whether stream channels are joined or expanded if
1.68 ratchov 131: the stream number of channels is not equal to the device number of channels.
132: If the flag is
133: .Va off
134: then stream channels are routed to the corresponding
135: device channel, possibly discarding channels not present in the device.
136: If the flag is
137: .Va on ,
138: then a single stream channel may be sent on multiple device channels,
139: or multiple stream channels may be sent to a single device channel.
140: For instance, this feature could be used to request mono streams to
141: be sent on multiple outputs or to record a stereo input into a mono stream.
142: The default is
143: .Ar on .
1.76 ratchov 144: .It Fl L Ar addr
145: Specify a local network address to listen on in server mode.
146: .Nm
147: will listen on TCP port 11025+n, where n is the unit number
148: specified with
149: .Fl U .
150: Without this option,
151: .Nm
152: listens on the
153: .Ux Ns -domain
154: socket only, and is not reachable from any network.
1.26 ratchov 155: .It Fl l
1.71 ratchov 156: Detach and become a daemon.
1.37 ratchov 157: .It Fl m Ar mode
1.66 ratchov 158: Set the stream mode.
1.37 ratchov 159: Valid modes are
1.39 jmc 160: .Ar play ,
161: .Ar rec ,
1.37 ratchov 162: and
1.66 ratchov 163: .Ar mon ,
164: corresponding to playback, recording and monitoring.
165: A monitoring stream is a fake recording stream corresponding to
166: the mix of all playback streams.
167: Multiple modes can be specified, separated by commas,
168: but the same stream cannot be used for both recording and monitoring.
1.37 ratchov 169: The default is
1.67 jmc 170: .Ar play , Ns Ar rec
1.66 ratchov 171: (i.e. full-duplex).
1.42 ratchov 172: .It Fl n
173: Loopback mode.
1.71 ratchov 174: Instead of using audio devices, send input streams
1.42 ratchov 175: to the output, processing them on the fly.
176: This mode is useful to mix, demultiplex, resample or reencode
1.43 jmc 177: audio files offline.
1.16 ratchov 178: .It Fl o Ar file
1.71 ratchov 179: Add this file to the list of recording streams.
1.16 ratchov 180: If the option argument is
181: .Sq -
182: then standard output will be used.
1.66 ratchov 183: .It Fl q Ar device
1.71 ratchov 184: Expose the audio device clock on this
1.66 ratchov 185: .Xr sndio 7
1.71 ratchov 186: MIDI port and allow audio device properties to be controlled
187: through MIDI.
188: This includes per-stream volumes and the ability to
189: synchronously start, stop and relocate streams created in
190: MIDI Machine
191: Control (MMC) slave mode
192: .Pq Fl t .
1.26 ratchov 193: .It Fl r Ar rate
1.71 ratchov 194: Sample rate in Hertz of the stream.
1.17 jmc 195: The default is 44100Hz.
1.57 ratchov 196: .It Fl s Ar name
197: Add
198: .Ar name
199: to the list of sub-devices to expose in server mode.
1.71 ratchov 200: This allows clients to use
201: .Nm
202: instead of the physical audio device for audio input and output
203: in order to share the physical device with other clients.
1.57 ratchov 204: Defining multiple sub-devices allows splitting a physical audio device
1.63 jmc 205: into logical devices having different properties (e.g. channel ranges).
1.57 ratchov 206: The given
207: .Ar name
1.62 ratchov 208: corresponds to the
1.57 ratchov 209: .Dq option
210: part of the
211: .Xr sndio 7
212: device name string.
1.62 ratchov 213: .It Fl t Ar mode
1.71 ratchov 214: Select the way streams are controlled by MIDI Machine Control (MMC)
1.67 jmc 215: messages.
1.62 ratchov 216: If the mode is
217: .Va off
218: (the default), then streams are not affected by MMC messages.
219: If the mode is
220: .Va slave ,
221: then streams are started synchronously by MMC start messages;
1.67 jmc 222: additionally, the server clock is exposed as MIDI Time Code (MTC)
1.62 ratchov 223: messages allowing MTC-capable software or hardware to be synchronized
224: to audio streams.
1.54 ratchov 225: .It Fl U Ar unit
226: Unit number to use when running in server mode.
227: Each
228: .Nm
229: server instance has an unique unit number,
230: used in
231: .Xr sndio 7
232: device names.
233: The default is 0.
1.16 ratchov 234: .It Fl u
1.21 jmc 235: Normally
236: .Nm
237: tries to automatically determine the optimal parameters for the audio device;
238: if this option is specified,
239: it will instead use the parameters specified by the
1.26 ratchov 240: .Fl Ccer
1.21 jmc 241: options.
1.30 ratchov 242: .It Fl v Ar volume
243: Software volume attenuation of the playback stream.
244: The value must be between 1 and 127,
1.31 jmc 245: corresponding to \-42dB and \-0dB attenuation.
1.33 ratchov 246: In server mode, clients inherit this parameter.
1.34 jmc 247: Reducing the volume in advance reduces a client's dynamic range,
248: but allows client volume to stay independent from the number
1.33 ratchov 249: of clients as long as their number is small enough.
1.34 jmc 250: A good compromise is to use \-4dB attenuation (12 volume units)
251: for each additional client expected
252: (115 if 2 clients are expected, 103 for 3 clients, and so on).
1.26 ratchov 253: .It Fl x Ar policy
1.22 ratchov 254: Action when the output stream cannot accept
1.26 ratchov 255: recorded data fast enough or the input stream
256: cannot provide data to play fast enough.
1.22 ratchov 257: If the policy
258: is
1.23 jmc 259: .Dq ignore
1.26 ratchov 260: (the default) then samples that cannot be written are discarded
261: and samples that cannot be read are replaced by silence.
1.22 ratchov 262: If the policy is
1.23 jmc 263: .Dq sync
1.72 jmc 264: then recorded samples are discarded,
265: but the same amount of silence will be written
1.22 ratchov 266: once the stream is unblocked, in order to reach the right position in time.
1.26 ratchov 267: Similarly silence is played, but the same amount of samples will be discarded
268: once the stream is unblocked.
1.22 ratchov 269: If the policy is
1.23 jmc 270: .Dq error
271: then the stream is closed permanently.
1.62 ratchov 272: .Pp
1.71 ratchov 273: If a stream is created with the
1.67 jmc 274: .Fl t
275: option,
1.63 jmc 276: the
1.62 ratchov 277: .Dq ignore
1.63 jmc 278: action is disabled for any stream connected to it
279: to ensure proper synchronization.
1.62 ratchov 280: .It Fl z Ar nframes
1.71 ratchov 281: The audio device block size in frames.
1.63 jmc 282: This is the number of frames between audio clock ticks,
283: i.e. the clock resolution.
1.71 ratchov 284: If a stream is created with the
1.67 jmc 285: .Fl t
286: option,
287: and MTC is used for synchronization, the clock
1.62 ratchov 288: resolution must be 96, 100 or 120 ticks per second for maximum
1.63 jmc 289: accuracy.
290: For instance, 120 ticks per second at 48000Hz corresponds
291: to a 400 frame block size.
1.21 jmc 292: .El
293: .Pp
1.71 ratchov 294: On the command line,
295: per-device parameters
296: .Pq Fl abz
297: must precede the device definition
298: .Pq Fl f ,
299: and per-stream parameters
300: .Pq Fl Ccehjmrtvx
301: must precede the stream definition
302: .Pq Fl ios .
303: MIDI ports
304: .Pq Fl q
1.75 okan 305: and stream definitions
1.71 ratchov 306: .Pq Fl ios
307: must precede the definition of the device
308: .Pq Fl f
309: to which they are attached.
310: Global parameters
1.74 ratchov 311: .Pq Fl dlnUu
1.71 ratchov 312: are position-independent.
313: .Pp
314: If no audio devices
315: .Pq Fl f
316: are specified,
317: settings are applied as if
318: the default device is specified as the last argument.
319: If no streams
320: .Pq Fl ios
321: are specified for a device, a default server sub-device is
322: created attached to it, meaning that
323: .Nm
324: behaves as an audio server.
325: The default
326: .Xr sndio 7
327: device is
328: .Pa aucat:0
329: .Pq also known as Pa aucat:0.default
330: .Pp
1.32 ratchov 331: If
332: .Nm
333: is sent
1.44 ratchov 334: .Dv SIGHUP ,
335: .Dv SIGINT
336: or
337: .Dv SIGTERM ,
1.32 ratchov 338: it terminates recording to files.
339: .Pp
1.20 jmc 340: File formats are specified using the
341: .Fl h
1.26 ratchov 342: option.
1.16 ratchov 343: The following file formats are supported:
1.66 ratchov 344: .Bl -tag -width s32lexxx -offset indent
1.16 ratchov 345: .It raw
346: Headerless file.
1.17 jmc 347: This format is recommended since it has no limitations.
1.16 ratchov 348: .It wav
349: Microsoft WAVE file format.
350: There are limitations inherent to the file format itself:
351: not all encodings are supported,
352: file sizes are limited to 2GB,
1.17 jmc 353: and the file must support the
1.16 ratchov 354: .Xr lseek 2
1.17 jmc 355: operation (e.g. pipes do not support it).
1.16 ratchov 356: .It auto
357: Try to guess, depending on the file name.
1.9 millert 358: .El
359: .Pp
1.20 jmc 360: Encodings are specified using the
361: .Fl e
1.26 ratchov 362: option.
1.16 ratchov 363: The following encodings are supported:
364: .Pp
1.66 ratchov 365: .Bl -tag -width s32lexxx -offset indent -compact
1.16 ratchov 366: .It s8
367: signed 8-bit
368: .It u8
369: unsigned 8-bit
370: .It s16le
371: signed 16-bit, little endian
372: .It u16le
373: unsigned 16-bit, little endian
374: .It s16be
375: signed 16-bit, big endian
376: .It u16be
377: unsigned 16-bit, big endian
378: .It s24le
379: signed 24-bit, stored in 4 bytes, little endian
380: .It u24le
381: unsigned 24-bit, stored in 4 bytes, little endian
382: .It s24be
383: signed 24-bit, stored in 4 bytes, big endian
384: .It u24be
385: unsigned 24-bit, stored in 4 bytes, big endian
386: .It s32le
387: signed 32-bit, little endian
388: .It u32le
389: unsigned 32-bit, little endian
390: .It s32be
391: signed 32-bit, big endian
392: .It u32be
393: unsigned 32-bit, big endian
394: .It s24le3
395: signed 24-bit, packed in 3 bytes, little endian
396: .It u24le3
397: unsigned 24-bit, packed in 3 bytes, big endian
398: .It s24be3
399: signed 24-bit, packed in 3 bytes, little endian
400: .It u24be3
401: unsigned 24-bit, packed in 3 bytes, big endian
402: .It s20le3
403: signed 20-bit, packed in 3 bytes, little endian
404: .It u20le3
405: unsigned 20-bit, packed in 3 bytes, big endian
406: .It s20be3
407: signed 20-bit, packed in 3 bytes, little endian
408: .It u20be3
409: unsigned 20-bit, packed in 3 bytes, big endian
410: .It s18le3
411: signed 18-bit, packed in 3 bytes, little endian
412: .It u18le3
413: unsigned 18-bit, packed in 3 bytes, big endian
414: .It s18be3
415: signed 18-bit, packed in 3 bytes, little endian
416: .It u18be3
417: unsigned 18-bit, packed in 3 bytes, big endian
418: .El
1.46 ratchov 419: .Sh SERVER MODE
1.71 ratchov 420: If at least one sub-device
421: .Pq Fl s
422: is exposed by
423: .Nm ,
424: including the case when no stream options are given,
425: then
1.46 ratchov 426: .Nm
1.71 ratchov 427: can be used as a server
1.46 ratchov 428: to overcome hardware limitations and allow applications
429: to run on fixed sample rate devices or on devices
430: supporting only unusual encodings.
1.69 ratchov 431: .Pp
1.46 ratchov 432: Certain applications, such as synthesis software,
433: require a low latency audio setup.
1.71 ratchov 434: To reduce the probability of buffer underruns or overruns, especially
435: on busy machines, the server can be started by the super-user, in which
436: case it will run with higher priority.
1.72 jmc 437: Any user will still be able to connect to it,
438: but for privacy reasons only one user may have
1.71 ratchov 439: connections to it at a given time.
1.55 ratchov 440: .Sh MIDI CONTROL
441: .Nm
1.71 ratchov 442: can expose the audio device clock on registered
443: MIDI ports
444: .Pq Fl q
445: and allows audio device properties to be controlled
446: through MIDI.
447: If running in server mode
1.62 ratchov 448: .Nm
1.71 ratchov 449: creates a MIDI port with the same name as the default audio
450: device to which MIDI programs can connect.
1.62 ratchov 451: .Pp
1.56 jmc 452: A MIDI channel is assigned to each stream, and the volume
1.55 ratchov 453: is changed using the standard volume controller (number 7).
1.71 ratchov 454: Similarly, when the audio client changes its volume,
1.55 ratchov 455: the same MIDI controller message is sent out; it can be used
1.56 jmc 456: for instance for monitoring or as feedback for motorized
1.55 ratchov 457: faders.
1.62 ratchov 458: .Pp
1.71 ratchov 459: Streams created with the
1.63 jmc 460: .Fl t
1.67 jmc 461: option are controlled by the following MMC messages:
1.66 ratchov 462: .Bl -tag -width relocateXXX -offset indent
1.62 ratchov 463: .It relocate
1.71 ratchov 464: Streams are relocated to the requested time postion
465: relative to the beginning of the stream, at which playback
1.62 ratchov 466: and recording must start.
1.71 ratchov 467: If the requested position is beyond the end of file,
468: the stream is temporarly disabled until a valid postion is requested.
469: This message is ignored by client streams (server mode).
470: The given time position is sent to MIDI ports as an MTC
1.62 ratchov 471: .Dq "full frame"
472: message forcing all MTC-slaves to relocate to the given
473: position (see below).
474: .It start
1.71 ratchov 475: Put all streams in starting mode.
476: In this mode,
477: .Nm
478: waits for all streams to become ready
1.62 ratchov 479: to start, and then starts them synchronously.
1.72 jmc 480: Once started, new streams can be created (server mode)
481: but they will be blocked
1.62 ratchov 482: until the next stop-to-start transition.
1.67 jmc 483: .It stop
1.71 ratchov 484: Put all streams in stopped mode (the default).
1.67 jmc 485: In this mode, any stream attempting to start playback or recording
486: is paused.
1.71 ratchov 487: Files are stopped and rewound back to the starting position,
488: while client streams (server mode) that are already
489: started are not affected until they stop and try to start again.
1.62 ratchov 490: .El
491: .Pp
1.71 ratchov 492: Streams created with the
1.63 jmc 493: .Fl t
1.67 jmc 494: option export the server clock using MTC, allowing non-audio
1.62 ratchov 495: software or hardware to be synchronized to the audio stream.
496: The following sample rates
497: .Pq Fl r
498: and block sizes
499: .Pq Fl z
500: are recommended for maximum accuracy:
501: .Pp
1.66 ratchov 502: .Bl -bullet -offset indent -compact
1.62 ratchov 503: .It
504: 44100Hz, 441 frames
505: .It
506: 48000Hz, 400 frames
507: .It
508: 48000Hz, 480 frames
509: .It
510: 48000Hz, 500 frames
511: .El
512: .Pp
513: For instance, the following command will create two devices:
514: the default
515: .Va aucat:0
1.63 jmc 516: and a MIDI-controlled
517: .Va aucat:0.mmc :
1.62 ratchov 518: .Bd -literal -offset indent
519: $ aucat -l -r 48000 -z 400 -s default -t slave -s mmc
520: .Ed
521: .Pp
522: Streams connected to
523: .Va aucat:0
524: behave normally, while streams connected to
525: .Va aucat:0.mmc
526: wait for the MMC start signal and start synchronously.
1.63 jmc 527: Regardless of which device a stream is connected to,
528: its playback volume knob is exposed.
1.66 ratchov 529: .Pp
530: For instance, the following command will play a file on the
531: .Va aucat:0.mmc
532: audio device, and give full control to MIDI software or hardware
533: connected to the
534: .Va midithru:0
535: MIDI device:
536: .Bd -literal -offset indent
1.70 ratchov 537: $ aucat -t slave -q midithru:0 -i file.wav -f aucat:0.mmc
1.66 ratchov 538: .Ed
539: .Pp
540: At this stage,
541: .Nm
542: will start, stop and relocate automatically following all user
543: actions in the MIDI sequencer.
544: Note that the sequencer must use
545: .Va aucat:0
546: as the MTC source, i.e. the audio server, not the audio player.
1.9 millert 547: .Sh ENVIRONMENT
1.76 ratchov 548: .Bl -tag -width "AUCAT_COOKIE" -compact
549: .It Ev AUCAT_COOKIE
1.77 ! jmc 550: File containing user's session cookie.
1.24 jmc 551: .It Ev AUDIODEVICE
1.57 ratchov 552: .Xr sndio 7
553: audio device to use if the
1.50 ratchov 554: .Fl f
555: option is not specified.
1.9 millert 556: .El
1.16 ratchov 557: .Sh EXAMPLES
1.77 ! jmc 558: Mix and play two stereo streams,
1.16 ratchov 559: the first at 48kHz and the second at 44.1kHz:
560: .Bd -literal -offset indent
561: $ aucat -r 48000 -i file1.raw -r 44100 -i file2.raw
562: .Ed
563: .Pp
1.77 ! jmc 564: Record channels 2 and 3 into one stereo file and
1.16 ratchov 565: channels 6 and 7 into another stereo file using a 96kHz sampling rate for
566: both:
567: .Bd -literal -offset indent
1.26 ratchov 568: $ aucat -r 96000 -C 2:3 -o file1.raw -C 6:7 -o file2.raw
1.42 ratchov 569: .Ed
570: .Pp
1.77 ! jmc 571: Split a stereo file into two mono files:
1.42 ratchov 572: .Bd -literal -offset indent
573: $ aucat -n -i stereo.wav -C 0:0 -o left.wav -C 1:1 -o right.wav
1.16 ratchov 574: .Ed
575: .Pp
1.77 ! jmc 576: Start
1.35 ratchov 577: .Nm
1.77 ! jmc 578: in server mode using default parameters, creating an
1.57 ratchov 579: additional sub-device for output to channels 2:3 only (rear speakers
580: on most cards), exposing the
581: .Pa aucat:0
582: and
583: .Pa aucat:0.rear
584: devices:
1.35 ratchov 585: .Bd -literal -offset indent
1.45 ratchov 586: $ aucat -l -s default -c 2:3 -s rear
1.35 ratchov 587: .Ed
588: .Pp
1.77 ! jmc 589: Start
1.35 ratchov 590: .Nm
1.77 ! jmc 591: in server mode, creating the default sub-device with low volume and
1.57 ratchov 592: an additional sub-device for high volume output, exposing the
593: .Pa aucat:0
594: and
595: .Pa aucat:0.max
596: devices:
1.35 ratchov 597: .Bd -literal -offset indent
1.45 ratchov 598: $ aucat -l -v 65 -s default -v 127 -s max
1.16 ratchov 599: .Ed
1.71 ratchov 600: .Pp
1.77 ! jmc 601: Start
1.71 ratchov 602: .Nm
1.77 ! jmc 603: in server mode, configuring the audio device to use
1.72 jmc 604: a 48kHz sample frequency, 240-frame block size,
605: and 2-block buffers.
1.71 ratchov 606: The corresponding latency is 10ms, which is
607: the time it takes the sound to propagate 3.5 meters.
608: .Bd -literal -offset indent
609: $ aucat -l -r 48000 -b 480 -z 240
610: .Ed
1.2 kstailey 611: .Sh SEE ALSO
1.12 jmc 612: .Xr audioctl 1 ,
1.17 jmc 613: .Xr cdio 1 ,
1.9 millert 614: .Xr mixerctl 1 ,
1.54 ratchov 615: .Xr audio 4 ,
616: .Xr sndio 7
1.16 ratchov 617: .Sh BUGS
618: The
1.1 kstailey 619: .Nm
1.16 ratchov 620: utility assumes non-blocking I/O for input and output streams.
621: It will not work reliably on files that may block
622: (ordinary files block, pipes don't).
1.71 ratchov 623: To avoid audio underruns/overruns or MIDI jitter caused by file I/O,
624: it's recommended to use two
625: .Nm
626: processes: a server handling audio and MIDI I/O and a client handling
627: disk I/O.
1.16 ratchov 628: .Pp
629: Resampling is low quality; down-sampling especially should be avoided
630: when recording.
631: .Pp
632: Processing is done using 16-bit arithmetic,
633: thus samples with more than 16 bits are rounded.
1.17 jmc 634: 16 bits (i.e. 97dB dynamic) are largely enough for most applications though.
1.71 ratchov 635: .Pp
636: If
637: .Fl a Ar off
1.72 jmc 638: is used in server mode,
1.71 ratchov 639: .Nm
1.72 jmc 640: creates sub-devices to expose first
641: and then opens the audio hardware on demand.
1.71 ratchov 642: Technically, this allows
643: .Nm
1.75 okan 644: to attempt to use one of the sub-devices it exposes as an audio device,
1.71 ratchov 645: creating a deadlock.
646: To avoid this,
647: .Fl a Ar off
648: is disabled for the default audio device, but nothing prevents the user
649: from shooting himself in the foot by creating a similar deadlock.
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