Codex

ALSALOOP

Section: User Commands (1)

Updated: 5 Aug 2010

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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 [email protected]='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 (capture card) to the ALSA layer (capture card). Format of ossmixid is ALSAID[,INDEX]@OSSID:

  "[email protected]"

  "PCM,[email protected]"

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 <[email protected]>. This document is by Jaroslav Kysela <[email protected]>.


Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

BUGS

AUTHOR


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