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ALSALOOP(1)									      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 (capture 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)
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