Annotation of src/usr.bin/aucat/aucat.1, Revision 1.75
1.75 ! okan 1: .\" $OpenBSD: aucat.1,v 1.74 2011/03/02 22:45:25 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: .\"
1.75 ! okan 17: .Dd $Mdocdate: March 2 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
1.37 ratchov 36: .Op Fl m Ar mode
1.16 ratchov 37: .Op Fl o Ar file
1.66 ratchov 38: .Op Fl q Ar device
1.16 ratchov 39: .Op Fl r Ar rate
1.57 ratchov 40: .Op Fl s Ar name
1.62 ratchov 41: .Op Fl t Ar mode
1.54 ratchov 42: .Op Fl U Ar unit
1.30 ratchov 43: .Op Fl v Ar volume
1.22 ratchov 44: .Op Fl x Ar policy
1.62 ratchov 45: .Op Fl z Ar nframes
1.16 ratchov 46: .Ek
1.1 kstailey 47: .Sh DESCRIPTION
1.9 millert 48: .Nm
1.71 ratchov 49: is an audio utility which can simultaneously play and record
50: any number of audio
51: .Em streams
52: on any number of audio devices,
53: possibly controlled through MIDI.
54: It can also act as an audio server, in which case streams
55: correspond to client connections rather than plain files.
56: .Pp
57: Audio devices are independent.
58: A list of streams is attached to each audio device,
59: as well as an optional list of MIDI ports to control the device.
60: A typical invocation of
61: .Nm
62: consists in providing streams to play and record,
63: and possibly the audio device to use, if the default is not desired.
64: .Pp
65: This also applies to server mode, except that streams are created
66: dynamically when clients connect to the server.
67: Thus, instead of actual streams (paths to plain files),
68: templates for client streams (sub-device names) must be provided.
1.17 jmc 69: .Pp
1.16 ratchov 70: The options are as follows:
1.26 ratchov 71: .Bl -tag -width Ds
1.70 ratchov 72: .It Fl a Ar flag
73: Control whether
74: .Nm
1.71 ratchov 75: opens the audio device only when needed or keeps it open all the time.
1.70 ratchov 76: If the flag is
77: .Va on
78: then the device is kept open all the time, ensuring no other program can
79: steal it.
80: If the flag is
81: .Va off ,
82: then it's automatically closed, allowing other programs to have direct
83: access to the device, or the device to be disconnected.
84: The default is
85: .Va on .
1.49 jmc 86: .It Fl b Ar nframes
1.66 ratchov 87: The buffer size of the audio device in frames.
1.49 jmc 88: A frame consists of one sample for each channel in the stream.
89: This is the number of frames that will be buffered before being played
90: and thus controls the playback latency.
1.25 jmc 91: .It Xo
92: .Fl C Ar min : Ns Ar max ,
93: .Fl c Ar min : Ns Ar max
94: .Xc
1.72 jmc 95: The range of stream channel numbers for recording and playback directions,
96: respectively.
1.17 jmc 97: The default is 0:1, i.e. stereo.
1.59 ratchov 98: .It Fl d
1.71 ratchov 99: Increase log verbosity.
1.59 ratchov 100: .Nm
1.75 ! okan 101: logs on
! 102: .Em stderr
! 103: until it daemonizes.
1.26 ratchov 104: .It Fl e Ar enc
105: Encoding of the playback or recording stream (see below).
1.17 jmc 106: The default is signed, 16-bit, native byte order.
107: .It Fl f Ar device
1.71 ratchov 108: Add this
1.57 ratchov 109: .Xr sndio 7
1.71 ratchov 110: audio device to devices used for playing and/or recording.
111: Preceding streams
112: .Pq Fl ios ,
113: control MIDI ports
114: .Pq Fl q ,
115: and per-device options
116: .Pq Fl abz
117: apply to this device.
118: Device mode and parameters are determined from streams
119: attached to it.
1.26 ratchov 120: .It Fl h Ar fmt
121: File format of the playback or record stream (see below).
1.17 jmc 122: The default is auto.
1.16 ratchov 123: .It Fl i Ar file
1.71 ratchov 124: Add this file to the list of streams to play.
1.16 ratchov 125: If the option argument is
126: .Sq -
127: then standard input will be used.
1.68 ratchov 128: .It Fl j Ar flag
1.71 ratchov 129: Control whether stream channels are joined or expanded if
1.68 ratchov 130: the stream number of channels is not equal to the device number of channels.
131: If the flag is
132: .Va off
133: then stream channels are routed to the corresponding
134: device channel, possibly discarding channels not present in the device.
135: If the flag is
136: .Va on ,
137: then a single stream channel may be sent on multiple device channels,
138: or multiple stream channels may be sent to a single device channel.
139: For instance, this feature could be used to request mono streams to
140: be sent on multiple outputs or to record a stereo input into a mono stream.
141: The default is
142: .Ar on .
1.26 ratchov 143: .It Fl l
1.71 ratchov 144: Detach and become a daemon.
1.37 ratchov 145: .It Fl m Ar mode
1.66 ratchov 146: Set the stream mode.
1.37 ratchov 147: Valid modes are
1.39 jmc 148: .Ar play ,
149: .Ar rec ,
1.37 ratchov 150: and
1.66 ratchov 151: .Ar mon ,
152: corresponding to playback, recording and monitoring.
153: A monitoring stream is a fake recording stream corresponding to
154: the mix of all playback streams.
155: Multiple modes can be specified, separated by commas,
156: but the same stream cannot be used for both recording and monitoring.
1.37 ratchov 157: The default is
1.67 jmc 158: .Ar play , Ns Ar rec
1.66 ratchov 159: (i.e. full-duplex).
1.42 ratchov 160: .It Fl n
161: Loopback mode.
1.71 ratchov 162: Instead of using audio devices, send input streams
1.42 ratchov 163: to the output, processing them on the fly.
164: This mode is useful to mix, demultiplex, resample or reencode
1.43 jmc 165: audio files offline.
1.16 ratchov 166: .It Fl o Ar file
1.71 ratchov 167: Add this file to the list of recording streams.
1.16 ratchov 168: If the option argument is
169: .Sq -
170: then standard output will be used.
1.66 ratchov 171: .It Fl q Ar device
1.71 ratchov 172: Expose the audio device clock on this
1.66 ratchov 173: .Xr sndio 7
1.71 ratchov 174: MIDI port and allow audio device properties to be controlled
175: through MIDI.
176: This includes per-stream volumes and the ability to
177: synchronously start, stop and relocate streams created in
178: MIDI Machine
179: Control (MMC) slave mode
180: .Pq Fl t .
1.26 ratchov 181: .It Fl r Ar rate
1.71 ratchov 182: Sample rate in Hertz of the stream.
1.17 jmc 183: The default is 44100Hz.
1.57 ratchov 184: .It Fl s Ar name
185: Add
186: .Ar name
187: to the list of sub-devices to expose in server mode.
1.71 ratchov 188: This allows clients to use
189: .Nm
190: instead of the physical audio device for audio input and output
191: in order to share the physical device with other clients.
1.57 ratchov 192: Defining multiple sub-devices allows splitting a physical audio device
1.63 jmc 193: into logical devices having different properties (e.g. channel ranges).
1.57 ratchov 194: The given
195: .Ar name
1.62 ratchov 196: corresponds to the
1.57 ratchov 197: .Dq option
198: part of the
199: .Xr sndio 7
200: device name string.
1.62 ratchov 201: .It Fl t Ar mode
1.71 ratchov 202: Select the way streams are controlled by MIDI Machine Control (MMC)
1.67 jmc 203: messages.
1.62 ratchov 204: If the mode is
205: .Va off
206: (the default), then streams are not affected by MMC messages.
207: If the mode is
208: .Va slave ,
209: then streams are started synchronously by MMC start messages;
1.67 jmc 210: additionally, the server clock is exposed as MIDI Time Code (MTC)
1.62 ratchov 211: messages allowing MTC-capable software or hardware to be synchronized
212: to audio streams.
1.54 ratchov 213: .It Fl U Ar unit
214: Unit number to use when running in server mode.
215: Each
216: .Nm
217: server instance has an unique unit number,
218: used in
219: .Xr sndio 7
220: device names.
221: The default is 0.
1.16 ratchov 222: .It Fl u
1.21 jmc 223: Normally
224: .Nm
225: tries to automatically determine the optimal parameters for the audio device;
226: if this option is specified,
227: it will instead use the parameters specified by the
1.26 ratchov 228: .Fl Ccer
1.21 jmc 229: options.
1.30 ratchov 230: .It Fl v Ar volume
231: Software volume attenuation of the playback stream.
232: The value must be between 1 and 127,
1.31 jmc 233: corresponding to \-42dB and \-0dB attenuation.
1.33 ratchov 234: In server mode, clients inherit this parameter.
1.34 jmc 235: Reducing the volume in advance reduces a client's dynamic range,
236: but allows client volume to stay independent from the number
1.33 ratchov 237: of clients as long as their number is small enough.
1.34 jmc 238: A good compromise is to use \-4dB attenuation (12 volume units)
239: for each additional client expected
240: (115 if 2 clients are expected, 103 for 3 clients, and so on).
1.26 ratchov 241: .It Fl x Ar policy
1.22 ratchov 242: Action when the output stream cannot accept
1.26 ratchov 243: recorded data fast enough or the input stream
244: cannot provide data to play fast enough.
1.22 ratchov 245: If the policy
246: is
1.23 jmc 247: .Dq ignore
1.26 ratchov 248: (the default) then samples that cannot be written are discarded
249: and samples that cannot be read are replaced by silence.
1.22 ratchov 250: If the policy is
1.23 jmc 251: .Dq sync
1.72 jmc 252: then recorded samples are discarded,
253: but the same amount of silence will be written
1.22 ratchov 254: once the stream is unblocked, in order to reach the right position in time.
1.26 ratchov 255: Similarly silence is played, but the same amount of samples will be discarded
256: once the stream is unblocked.
1.22 ratchov 257: If the policy is
1.23 jmc 258: .Dq error
259: then the stream is closed permanently.
1.62 ratchov 260: .Pp
1.71 ratchov 261: If a stream is created with the
1.67 jmc 262: .Fl t
263: option,
1.63 jmc 264: the
1.62 ratchov 265: .Dq ignore
1.63 jmc 266: action is disabled for any stream connected to it
267: to ensure proper synchronization.
1.62 ratchov 268: .It Fl z Ar nframes
1.71 ratchov 269: The audio device block size in frames.
1.63 jmc 270: This is the number of frames between audio clock ticks,
271: i.e. the clock resolution.
1.71 ratchov 272: If a stream is created with the
1.67 jmc 273: .Fl t
274: option,
275: and MTC is used for synchronization, the clock
1.62 ratchov 276: resolution must be 96, 100 or 120 ticks per second for maximum
1.63 jmc 277: accuracy.
278: For instance, 120 ticks per second at 48000Hz corresponds
279: to a 400 frame block size.
1.21 jmc 280: .El
281: .Pp
1.71 ratchov 282: On the command line,
283: per-device parameters
284: .Pq Fl abz
285: must precede the device definition
286: .Pq Fl f ,
287: and per-stream parameters
288: .Pq Fl Ccehjmrtvx
289: must precede the stream definition
290: .Pq Fl ios .
291: MIDI ports
292: .Pq Fl q
1.75 ! okan 293: and stream definitions
1.71 ratchov 294: .Pq Fl ios
295: must precede the definition of the device
296: .Pq Fl f
297: to which they are attached.
298: Global parameters
1.74 ratchov 299: .Pq Fl dlnUu
1.71 ratchov 300: are position-independent.
301: .Pp
302: If no audio devices
303: .Pq Fl f
304: are specified,
305: settings are applied as if
306: the default device is specified as the last argument.
307: If no streams
308: .Pq Fl ios
309: are specified for a device, a default server sub-device is
310: created attached to it, meaning that
311: .Nm
312: behaves as an audio server.
313: The default
314: .Xr sndio 7
315: device is
316: .Pa aucat:0
317: .Pq also known as Pa aucat:0.default
318: .Pp
1.32 ratchov 319: If
320: .Nm
321: is sent
1.44 ratchov 322: .Dv SIGHUP ,
323: .Dv SIGINT
324: or
325: .Dv SIGTERM ,
1.32 ratchov 326: it terminates recording to files.
327: .Pp
1.20 jmc 328: File formats are specified using the
329: .Fl h
1.26 ratchov 330: option.
1.16 ratchov 331: The following file formats are supported:
1.66 ratchov 332: .Bl -tag -width s32lexxx -offset indent
1.16 ratchov 333: .It raw
334: Headerless file.
1.17 jmc 335: This format is recommended since it has no limitations.
1.16 ratchov 336: .It wav
337: Microsoft WAVE file format.
338: There are limitations inherent to the file format itself:
339: not all encodings are supported,
340: file sizes are limited to 2GB,
1.17 jmc 341: and the file must support the
1.16 ratchov 342: .Xr lseek 2
1.17 jmc 343: operation (e.g. pipes do not support it).
1.16 ratchov 344: .It auto
345: Try to guess, depending on the file name.
1.9 millert 346: .El
347: .Pp
1.20 jmc 348: Encodings are specified using the
349: .Fl e
1.26 ratchov 350: option.
1.16 ratchov 351: The following encodings are supported:
352: .Pp
1.66 ratchov 353: .Bl -tag -width s32lexxx -offset indent -compact
1.16 ratchov 354: .It s8
355: signed 8-bit
356: .It u8
357: unsigned 8-bit
358: .It s16le
359: signed 16-bit, little endian
360: .It u16le
361: unsigned 16-bit, little endian
362: .It s16be
363: signed 16-bit, big endian
364: .It u16be
365: unsigned 16-bit, big endian
366: .It s24le
367: signed 24-bit, stored in 4 bytes, little endian
368: .It u24le
369: unsigned 24-bit, stored in 4 bytes, little endian
370: .It s24be
371: signed 24-bit, stored in 4 bytes, big endian
372: .It u24be
373: unsigned 24-bit, stored in 4 bytes, big endian
374: .It s32le
375: signed 32-bit, little endian
376: .It u32le
377: unsigned 32-bit, little endian
378: .It s32be
379: signed 32-bit, big endian
380: .It u32be
381: unsigned 32-bit, big endian
382: .It s24le3
383: signed 24-bit, packed in 3 bytes, little endian
384: .It u24le3
385: unsigned 24-bit, packed in 3 bytes, big endian
386: .It s24be3
387: signed 24-bit, packed in 3 bytes, little endian
388: .It u24be3
389: unsigned 24-bit, packed in 3 bytes, big endian
390: .It s20le3
391: signed 20-bit, packed in 3 bytes, little endian
392: .It u20le3
393: unsigned 20-bit, packed in 3 bytes, big endian
394: .It s20be3
395: signed 20-bit, packed in 3 bytes, little endian
396: .It u20be3
397: unsigned 20-bit, packed in 3 bytes, big endian
398: .It s18le3
399: signed 18-bit, packed in 3 bytes, little endian
400: .It u18le3
401: unsigned 18-bit, packed in 3 bytes, big endian
402: .It s18be3
403: signed 18-bit, packed in 3 bytes, little endian
404: .It u18be3
405: unsigned 18-bit, packed in 3 bytes, big endian
406: .El
1.46 ratchov 407: .Sh SERVER MODE
1.71 ratchov 408: If at least one sub-device
409: .Pq Fl s
410: is exposed by
411: .Nm ,
412: including the case when no stream options are given,
413: then
1.46 ratchov 414: .Nm
1.71 ratchov 415: can be used as a server
1.46 ratchov 416: to overcome hardware limitations and allow applications
417: to run on fixed sample rate devices or on devices
418: supporting only unusual encodings.
1.69 ratchov 419: .Pp
1.46 ratchov 420: Certain applications, such as synthesis software,
421: require a low latency audio setup.
1.71 ratchov 422: To reduce the probability of buffer underruns or overruns, especially
423: on busy machines, the server can be started by the super-user, in which
424: case it will run with higher priority.
1.72 jmc 425: Any user will still be able to connect to it,
426: but for privacy reasons only one user may have
1.71 ratchov 427: connections to it at a given time.
1.55 ratchov 428: .Sh MIDI CONTROL
429: .Nm
1.71 ratchov 430: can expose the audio device clock on registered
431: MIDI ports
432: .Pq Fl q
433: and allows audio device properties to be controlled
434: through MIDI.
435: If running in server mode
1.62 ratchov 436: .Nm
1.71 ratchov 437: creates a MIDI port with the same name as the default audio
438: device to which MIDI programs can connect.
1.62 ratchov 439: .Pp
1.56 jmc 440: A MIDI channel is assigned to each stream, and the volume
1.55 ratchov 441: is changed using the standard volume controller (number 7).
1.71 ratchov 442: Similarly, when the audio client changes its volume,
1.55 ratchov 443: the same MIDI controller message is sent out; it can be used
1.56 jmc 444: for instance for monitoring or as feedback for motorized
1.55 ratchov 445: faders.
1.62 ratchov 446: .Pp
1.71 ratchov 447: Streams created with the
1.63 jmc 448: .Fl t
1.67 jmc 449: option are controlled by the following MMC messages:
1.66 ratchov 450: .Bl -tag -width relocateXXX -offset indent
1.62 ratchov 451: .It relocate
1.71 ratchov 452: Streams are relocated to the requested time postion
453: relative to the beginning of the stream, at which playback
1.62 ratchov 454: and recording must start.
1.71 ratchov 455: If the requested position is beyond the end of file,
456: the stream is temporarly disabled until a valid postion is requested.
457: This message is ignored by client streams (server mode).
458: The given time position is sent to MIDI ports as an MTC
1.62 ratchov 459: .Dq "full frame"
460: message forcing all MTC-slaves to relocate to the given
461: position (see below).
462: .It start
1.71 ratchov 463: Put all streams in starting mode.
464: In this mode,
465: .Nm
466: waits for all streams to become ready
1.62 ratchov 467: to start, and then starts them synchronously.
1.72 jmc 468: Once started, new streams can be created (server mode)
469: but they will be blocked
1.62 ratchov 470: until the next stop-to-start transition.
1.67 jmc 471: .It stop
1.71 ratchov 472: Put all streams in stopped mode (the default).
1.67 jmc 473: In this mode, any stream attempting to start playback or recording
474: is paused.
1.71 ratchov 475: Files are stopped and rewound back to the starting position,
476: while client streams (server mode) that are already
477: started are not affected until they stop and try to start again.
1.62 ratchov 478: .El
479: .Pp
1.71 ratchov 480: Streams created with the
1.63 jmc 481: .Fl t
1.67 jmc 482: option export the server clock using MTC, allowing non-audio
1.62 ratchov 483: software or hardware to be synchronized to the audio stream.
484: The following sample rates
485: .Pq Fl r
486: and block sizes
487: .Pq Fl z
488: are recommended for maximum accuracy:
489: .Pp
1.66 ratchov 490: .Bl -bullet -offset indent -compact
1.62 ratchov 491: .It
492: 44100Hz, 441 frames
493: .It
494: 48000Hz, 400 frames
495: .It
496: 48000Hz, 480 frames
497: .It
498: 48000Hz, 500 frames
499: .El
500: .Pp
501: For instance, the following command will create two devices:
502: the default
503: .Va aucat:0
1.63 jmc 504: and a MIDI-controlled
505: .Va aucat:0.mmc :
1.62 ratchov 506: .Bd -literal -offset indent
507: $ aucat -l -r 48000 -z 400 -s default -t slave -s mmc
508: .Ed
509: .Pp
510: Streams connected to
511: .Va aucat:0
512: behave normally, while streams connected to
513: .Va aucat:0.mmc
514: wait for the MMC start signal and start synchronously.
1.63 jmc 515: Regardless of which device a stream is connected to,
516: its playback volume knob is exposed.
1.66 ratchov 517: .Pp
518: For instance, the following command will play a file on the
519: .Va aucat:0.mmc
520: audio device, and give full control to MIDI software or hardware
521: connected to the
522: .Va midithru:0
523: MIDI device:
524: .Bd -literal -offset indent
1.70 ratchov 525: $ aucat -t slave -q midithru:0 -i file.wav -f aucat:0.mmc
1.66 ratchov 526: .Ed
527: .Pp
528: At this stage,
529: .Nm
530: will start, stop and relocate automatically following all user
531: actions in the MIDI sequencer.
532: Note that the sequencer must use
533: .Va aucat:0
534: as the MTC source, i.e. the audio server, not the audio player.
1.9 millert 535: .Sh ENVIRONMENT
1.35 ratchov 536: .Bl -tag -width "AUDIODEVICE" -compact
1.24 jmc 537: .It Ev AUDIODEVICE
1.57 ratchov 538: .Xr sndio 7
539: audio device to use if the
1.50 ratchov 540: .Fl f
541: option is not specified.
1.9 millert 542: .El
1.16 ratchov 543: .Sh EXAMPLES
544: The following will mix and play two stereo streams,
545: the first at 48kHz and the second at 44.1kHz:
546: .Bd -literal -offset indent
547: $ aucat -r 48000 -i file1.raw -r 44100 -i file2.raw
548: .Ed
549: .Pp
550: The following will record channels 2 and 3 into one stereo file and
551: channels 6 and 7 into another stereo file using a 96kHz sampling rate for
552: both:
553: .Bd -literal -offset indent
1.26 ratchov 554: $ aucat -r 96000 -C 2:3 -o file1.raw -C 6:7 -o file2.raw
1.42 ratchov 555: .Ed
556: .Pp
1.43 jmc 557: The following will split a stereo file into two mono files:
1.42 ratchov 558: .Bd -literal -offset indent
559: $ aucat -n -i stereo.wav -C 0:0 -o left.wav -C 1:1 -o right.wav
1.16 ratchov 560: .Ed
561: .Pp
1.35 ratchov 562: The following will start
563: .Nm
1.40 jmc 564: in server mode using default parameters, but will create an
1.57 ratchov 565: additional sub-device for output to channels 2:3 only (rear speakers
566: on most cards), exposing the
567: .Pa aucat:0
568: and
569: .Pa aucat:0.rear
570: devices:
1.35 ratchov 571: .Bd -literal -offset indent
1.45 ratchov 572: $ aucat -l -s default -c 2:3 -s rear
1.35 ratchov 573: .Ed
574: .Pp
575: The following will start
576: .Nm
1.57 ratchov 577: in server mode creating the default sub-device with low volume and
578: an additional sub-device for high volume output, exposing the
579: .Pa aucat:0
580: and
581: .Pa aucat:0.max
582: devices:
1.35 ratchov 583: .Bd -literal -offset indent
1.45 ratchov 584: $ aucat -l -v 65 -s default -v 127 -s max
1.16 ratchov 585: .Ed
1.71 ratchov 586: .Pp
587: The following will start
588: .Nm
589: in server mode configuring the audio device to use
1.72 jmc 590: a 48kHz sample frequency, 240-frame block size,
591: and 2-block buffers.
1.71 ratchov 592: The corresponding latency is 10ms, which is
593: the time it takes the sound to propagate 3.5 meters.
594: .Bd -literal -offset indent
595: $ aucat -l -r 48000 -b 480 -z 240
596: .Ed
1.2 kstailey 597: .Sh SEE ALSO
1.12 jmc 598: .Xr audioctl 1 ,
1.17 jmc 599: .Xr cdio 1 ,
1.9 millert 600: .Xr mixerctl 1 ,
1.54 ratchov 601: .Xr audio 4 ,
602: .Xr sndio 7
1.16 ratchov 603: .Sh BUGS
604: The
1.1 kstailey 605: .Nm
1.16 ratchov 606: utility assumes non-blocking I/O for input and output streams.
607: It will not work reliably on files that may block
608: (ordinary files block, pipes don't).
1.71 ratchov 609: To avoid audio underruns/overruns or MIDI jitter caused by file I/O,
610: it's recommended to use two
611: .Nm
612: processes: a server handling audio and MIDI I/O and a client handling
613: disk I/O.
1.16 ratchov 614: .Pp
615: Resampling is low quality; down-sampling especially should be avoided
616: when recording.
617: .Pp
618: Processing is done using 16-bit arithmetic,
619: thus samples with more than 16 bits are rounded.
1.17 jmc 620: 16 bits (i.e. 97dB dynamic) are largely enough for most applications though.
1.71 ratchov 621: .Pp
622: If
623: .Fl a Ar off
1.72 jmc 624: is used in server mode,
1.71 ratchov 625: .Nm
1.72 jmc 626: creates sub-devices to expose first
627: and then opens the audio hardware on demand.
1.71 ratchov 628: Technically, this allows
629: .Nm
1.75 ! okan 630: to attempt to use one of the sub-devices it exposes as an audio device,
1.71 ratchov 631: creating a deadlock.
632: To avoid this,
633: .Fl a Ar off
634: is disabled for the default audio device, but nothing prevents the user
635: from shooting himself in the foot by creating a similar deadlock.
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