ALSALOOP(1)                 General Commands Manual                ALSALOOP(1)



NAME
       alsaloop - command-line PCM loopback

SYNOPSIS
       alsaloop [-option] [cmd]

DESCRIPTION
       alsaloop  allows create a PCM loopback between a PCM capture device and
       a PCM playback device.

       alsaloop supports multiple soundcards, adaptive clock  synchronization,
       adaptive  rate resampling using the samplerate library (if available in
       the system). Also, mixer controls can be redirected from  one  card  to
       another (for example Master and PCM).


OPTIONS
       -h | --help

              Prints the help information.


       -g <file> | --config=<file>

              Use given configuration file. The syntax of this file is simple:
              one line contains the command line options for one job. The  '#'
              means comment and rest of line is ignored. Example:

                # First line - comment, second line - first job
                -C hw:1,0 -P hw:0,0 -t 50000 -T 1
                # Third line - comment, fourth line - second job
                -C hw:1,1 -P hw:0,1 -t 40000 -T 2


       -d | --daemonize

              Daemonize the main process and use syslog for messages.


       -P <device> | --pdevice=<device>

              Use given playback device.


       -C <device> | --cdevice=<device>

              Use given capture device.


       -X <device> | --pctl=<device>

              Use given CTL device for playback.


       -Y <device> | --cctl=<device>

              Use given CTL device for capture.


       -l <latency> | --latency=<frames>

              Requested latency in frames.


       -t <usec> | --tlatency=<usec>

              Requested latency in usec (1/1000000sec).


       -f <format> | --format=<format>

              Format specification (usually S16_LE S32_LE). Use -h to list all
              formats.  Default format is S16_LE.


       -c <channels> | --channels=<channels>

              Channel count specification. Default value is 2.


       -c <rate> | --rate=<rate>

              Rate specification. Default value is 48000 (Hz).


       -n | --resample

              Allow rate resampling using alsa-lib.


       -A <converter> | --samplerate=<converter>

              Use libsamplerate and choose a converter:

                0 or sincbest     - best quality
                1 or sincmedium   - medium quality
                2 or sincfastest  - lowest quality
                3 or zerohold     - hold zero samples
                4 or linear       - worst quality - linear resampling
                5 or auto         - choose best method


       -B <size> | --buffer=<size>

              Buffer size in frames.


       -E <size> | --period=<size>

              Period size in frames.


       -s <secs> | --seconds=<secs>

              Duration of loop in seconds.


       -b | --nblock

              Non-block mode (very early process wakeup). Eats more CPU.


       -S <mode> | --sync=<mode>

              Sync mode specification for capture to playback stream:
                0 or none       - do not touch the stream
                1 or simple     - add or remove samples to keep
                                  both streams synchronized
                2 or captshift  - use driver for the capture device
                                  (if supported) to compensate
                                  the rate shift
                3 or playshift  - use driver for the playback device
                                  (if supported) to compensate
                                  the rate shift
                4 or samplerate - use samplerate library to do rate resampling
                5 or auto       - automatically selects the best method
                                  in this order: captshift, playshift,
                                  samplerate, simple


       -T <num> | --thread=<num>

              Thread number (-1 means create a unique thread). All  jobs  with
              same thread numbers are run within one thread.


       -m <mixid> | --mixer=<midid>

              Redirect  mixer  control  from  the playback card to the capture
              card. Format of mixid is SRCID(PLAYBACK)[@DSTID(PLAYBACK)]:

                "name='Master Playback Switch'@name='Another Switch'"
                "name='PCM Playback Volume'"

              Known attributes:

                name      - control ID name
                index     - control ID index
                device    - control ID device
                subdevice - control ID subdevice
                iface     - control ID interface
                numid     - control ID numid


       -O <ossmixid> | --ossmixer=<midid>

              Redirect mixer control from the OSS Mixer emulation layer  (cap-
              ture  card) to the ALSA layer (capture card). Format of ossmixid
              is ALSAID[,INDEX]@OSSID:

                "Master@VOLUME"
                "PCM,1@ALTPCM"

              Known OSS attributes:

                VOLUME, BASS, TREBLE, SYNTH,  PCM,  SPEAKER,  LINE,  MIC,  CD,
              IMIX, ALTPCM,
                RECLEV, IGAIN, OGAIN, LINE1, LINE2, LINE3, DIGITAL1, DIGITAL2,
              DIGITAL3,
                PHONEIN, PHONEOUT, VIDEO, RADIO, MONITOR


       -v | --verbose

              Verbose mode. Use multiple times to increase verbosity.



       -U | --xrun

              Verbose xrun profiling.


       -W <timeout> | --wake=<timeout>

              Set process wake timeout.


EXAMPLES
       alsaloop -C hw:0,0 -P hw:1,0 -t 50000


BUGS
       None known.

AUTHOR
       alsaloop is by Jaroslav Kysela <perex@perex.cz>.  This document  is  by
       Jaroslav Kysela <perex@perex.cz>.



                                  5 Aug 2010                       ALSALOOP(1)
