1ALSALOOP(1)                 General Commands Manual                ALSALOOP(1)
2
3
4

NAME

6       alsaloop - command-line PCM loopback
7

SYNOPSIS

9       alsaloop [-option] [cmd]
10

DESCRIPTION

12       alsaloop  allows create a PCM loopback between a PCM capture device and
13       a PCM playback device.
14
15       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).
19
20

OPTIONS

22       -h | --help
23
24              Prints the help information.
25
26
27       -g <file> | --config=<file>
28
29              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
33                # 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
38
39       -d | --daemonize
40
41              Daemonize the main process and use syslog for messages.
42
43
44       -P <device> | --pdevice=<device>
45
46              Use given playback device.
47
48
49       -C <device> | --cdevice=<device>
50
51              Use given capture device.
52
53
54       -X <device> | --pctl=<device>
55
56              Use given CTL device for playback.
57
58
59       -Y <device> | --cctl=<device>
60
61              Use given CTL device for capture.
62
63
64       -l <latency> | --latency=<frames>
65
66              Requested latency in frames.
67
68
69       -t <usec> | --tlatency=<usec>
70
71              Requested latency in usec (1/1000000sec).
72
73
74       -f <format> | --format=<format>
75
76              Format specification (usually S16_LE S32_LE). Use -h to list all
77              formats.  Default format is S16_LE.
78
79
80       -c <channels> | --channels=<channels>
81
82              Channel count specification. Default value is 2.
83
84
85       -c <rate> | --rate=<rate>
86
87              Rate specification. Default value is 48000 (Hz).
88
89
90       -n | --resample
91
92              Allow rate resampling using alsa-lib.
93
94
95       -A <converter> | --samplerate=<converter>
96
97              Use libsamplerate and choose a converter:
98
99                0 or sincbest     - best quality
100                1 or sincmedium   - medium quality
101                2 or sincfastest  - lowest quality
102                3 or zerohold     - hold zero samples
103                4 or linear       - worst quality - linear resampling
104                5 or auto         - choose best method
105
106
107       -B <size> | --buffer=<size>
108
109              Buffer size in frames.
110
111
112       -E <size> | --period=<size>
113
114              Period size in frames.
115
116
117       -s <secs> | --seconds=<secs>
118
119              Duration of loop in seconds.
120
121
122       -b | --nblock
123
124              Non-block mode (very early process wakeup). Eats more CPU.
125
126
127       -S <mode> | --sync=<mode>
128
129              Sync mode specification for capture to playback stream:
130                0 or none       - do not touch the stream
131                1 or simple     - add or remove samples to keep
132                                  both streams synchronized
133                2 or captshift  - use driver for the capture device
134                                  (if supported) to compensate
135                                  the rate shift
136                3 or playshift  - use driver for the playback device
137                                  (if supported) to compensate
138                                  the rate shift
139                4 or samplerate - use samplerate library to do rate resampling
140                5 or auto       - automatically selects the best method
141                                  in this order: captshift, playshift,
142                                  samplerate, simple
143
144
145       -T <num> | --thread=<num>
146
147              Thread number (-1 means create a unique thread). All  jobs  with
148              same thread numbers are run within one thread.
149
150
151       -m <mixid> | --mixer=<midid>
152
153              Redirect  mixer  control  from  the playback card to the capture
154              card. Format of mixid is SRCID(PLAYBACK)[@DSTID(PLAYBACK)]:
155
156                "name='Master Playback Switch'@name='Another Switch'"
157                "name='PCM Playback Volume'"
158
159              Known attributes:
160
161                name      - control ID name
162                index     - control ID index
163                device    - control ID device
164                subdevice - control ID subdevice
165                iface     - control ID interface
166                numid     - control ID numid
167
168
169       -O <ossmixid> | --ossmixer=<midid>
170
171              Redirect mixer control from the OSS Mixer emulation layer  (cap‐
172              ture  card) to the ALSA layer (capture card). Format of ossmixid
173              is ALSAID[,INDEX]@OSSID:
174
175                "Master@VOLUME"
176                "PCM,1@ALTPCM"
177
178              Known OSS attributes:
179
180                VOLUME, BASS, TREBLE, SYNTH,  PCM,  SPEAKER,  LINE,  MIC,  CD,
181              IMIX, ALTPCM,
182                RECLEV, IGAIN, OGAIN, LINE1, LINE2, LINE3, DIGITAL1, DIGITAL2,
183              DIGITAL3,
184                PHONEIN, PHONEOUT, VIDEO, RADIO, MONITOR
185
186
187       -v | --verbose
188
189              Verbose mode. Use multiple times to increase verbosity.
190
191
192
193       -U | --xrun
194
195              Verbose xrun profiling.
196
197
198       -W <timeout> | --wake=<timeout>
199
200              Set process wake timeout.
201
202

EXAMPLES

204       alsaloop -C hw:0,0 -P hw:1,0 -t 50000
205
206

BUGS

208       None known.
209

AUTHOR

211       alsaloop is by Jaroslav Kysela <perex@perex.cz>.  This document  is  by
212       Jaroslav Kysela <perex@perex.cz>.
213
214
215
216                                  5 Aug 2010                       ALSALOOP(1)