1ALSALOOP(1) General Commands Manual ALSALOOP(1)
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6 alsaloop - command-line PCM loopback
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9 alsaloop [-option] [cmd]
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12 alsaloop allows create a PCM loopback between a PCM capture device and
13 a PCM playback device.
14 alsaloop supports multiple soundcards, adaptive clock synchronization,
16 adaptive rate resampling using the samplerate library (if available in
17 the system). Also, mixer controls can be redirected from one card to
18 another (for example Master and PCM).
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22 -h | --help
23 Prints the help information.
25 -g <file> | --config=<file>
28 Use given configuration file. The syntax of this file is simple:
30 one line contains the command line options for one job. The '#'
31 means comment and rest of line is ignored. Example:
32 # First line - comment, second line - first job
34 -C hw:1,0 -P hw:0,0 -t 50000 -T 1
35 # Third line - comment, fourth line - second job
36 -C hw:1,1 -P hw:0,1 -t 40000 -T 2
37 -d | --daemonize
40 Daemonize the main process and use syslog for messages.
42 -P <device> | --pdevice=<device>
45 Use given playback device.
47 -C <device> | --cdevice=<device>
50 Use given capture device.
52 -X <device> | --pctl=<device>
55 Use given CTL device for playback.
57 -Y <device> | --cctl=<device>
60 Use given CTL device for capture.
62 -x <ctl_ascii_name> | --prateshift=<ctl_ascii_name>
65 Specify ctl ascii name for playshift sync mode (see the Examples
67 section).
68 -l <latency> | --latency=<frames>
71 Requested latency in frames.
73 -t <usec> | --tlatency=<usec>
76 Requested latency in usec (1/1000000sec).
78 -f <format> | --format=<format>
81 Format specification (usually S16_LE S32_LE). Use -h to list all
83 formats. Default format is S16_LE.
84 -c <channels> | --channels=<channels>
87 Channel count specification. Default value is 2.
89 -r <rate> | --rate=<rate>
92 Rate specification. Default value is 48000 (Hz).
94 -n | --resample
97 Allow rate resampling using alsa-lib.
99 -A <converter> | --samplerate=<converter>
102 Use libsamplerate and choose a converter:
104 0 or sincbest - best quality
106 1 or sincmedium - medium quality
107 2 or sincfastest - lowest quality
108 3 or zerohold - hold zero samples
109 4 or linear - worst quality - linear resampling
110 5 or auto - choose best method
111 -B <size> | --buffer=<size>
114 Buffer size in frames.
116 -E <size> | --period=<size>
119 Period size in frames.
121 -s <secs> | --seconds=<secs>
124 Duration of loop in seconds.
126 -b | --nblock
129 Non-block mode (very early process wakeup). Eats more CPU.
131 -S <mode> | --sync=<mode>
134 Sync mode specification for capture to playback stream:
136 0 or none - do not touch the stream
137 1 or simple - add or remove samples to keep
138 both streams synchronized
139 2 or captshift - use driver for the capture device
140 (if supported) to compensate
141 the rate shift
142 3 or playshift - use driver for the playback device
143 (if supported) to compensate
144 the rate shift
145 4 or samplerate - use samplerate library to do rate resampling
146 5 or auto - automatically selects the best method
147 in this order: captshift, playshift,
148 samplerate, simple
149 -T <num> | --thread=<num>
152 Thread number (-1 means create a unique thread). All jobs with
154 same thread numbers are run within one thread.
155 -m <mixid> | --mixer=<midid>
158 Redirect mixer control from the playback card to the capture
160 card. Format of mixid is SRCID(PLAYBACK)[@DSTID(PLAYBACK)]:
161 "name='Master Playback Switch'@name='Another Switch'"
163 "name='PCM Playback Volume'"
164 Known attributes:
166 name - control ID name
168 index - control ID index
169 device - control ID device
170 subdevice - control ID subdevice
171 iface - control ID interface
172 numid - control ID numid
173 -O <ossmixid> | --ossmixer=<midid>
176 Redirect mixer control from the OSS Mixer emulation layer (cap‐
178 ture card) to the ALSA layer (capture card). Format of ossmixid
179 is ALSAID[,INDEX]@OSSID:
180 "Master@VOLUME"
182 "PCM,1@ALTPCM"
183 Known OSS attributes:
185 VOLUME, BASS, TREBLE, SYNTH, PCM, SPEAKER, LINE, MIC, CD,
187 IMIX, ALTPCM,
188 RECLEV, IGAIN, OGAIN, LINE1, LINE2, LINE3, DIGITAL1, DIGITAL2,
189 DIGITAL3,
190 PHONEIN, PHONEOUT, VIDEO, RADIO, MONITOR
191 -v | --verbose
194 Verbose mode. Use multiple times to increase verbosity.
196 -U | --xrun
200 Verbose xrun profiling.
202 -W <timeout> | --wake=<timeout>
205 Set process wake timeout.
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210 alsaloop -C hw:0,0 -P hw:1,0 -t 50000
211 alsaloop -C hw:soundcard,0 -P hw:Loopback,0 -t 50000 -S playshift \
213 -x iface=PCM,name='PCM Rate Shift 100000',device=1
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216 None known.
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219 alsaloop is by Jaroslav Kysela <perex@perex.cz>. This document is by
220 Jaroslav Kysela <perex@perex.cz>.
221 5 Aug 2010 ALSALOOP(1)