oss_imux(7)							    OSS Devices 						       oss_imux(7)

NAME

       oss_imux - Input Muplexer audio driver.

DESCRIPTION

       IMUX  is  a  virtual  recording engine that permits up to 8 audio recording applications to run at the same time. Generally most soundcards
       permit only a single recording application to record the input source (via mic, line or CD).  With IMUX, you can  use  up  to  8  recording
       applications  to record the same source in different sample rates, bits/sample and channels (mono/stereo).  IMUX does all the rate and for-
       mat conversion in software. The applications think that they are actually getting data from the physical device. For instance, if you  want
       to  record  the input from a CDROM in .wav format at 48Khz/8/Mono and at the same time you want to record the same stream in .mp3 format in
       44.1Khz 16 bit stereo, with IMUX, you can start the wave recording application on the first IMUX device and start the MP3  encoder  on  the
       second IMUX device and both applications will run simultaneously thinking that they are getting data from the physical soundcard.

CONFIGURATION

       To add the IMUX driver you first need to ensure that there is a physical soundcard present and then you can run ossdetect -i to add it. You
       may want to select a master device by setting imux_masterdev, but the autodetection should provide a good default. After OSS restart,  imux
       should be available.

USAGE

       Connect	an  input  source  to the soundcard's line-in jack. Using the Mixer app like ossmix (or any OSS compliant mixer) set the recording
       source to Line-In (eg ossmix line.rec ON) Now you can start recording the input in multiple formats and at different sample rates. The sim-
       plest example is:

	       ossrecord -s48000 -b16 -c2 -d/dev/oss/oss_imux0/pcmin0 test1.wav &
	       ossrecord -s8000 -b8 -d/dev/oss/oss_imux0/pcmin0 test2.wav &

       After a few minutes of recording you can stop them by placing the command in forground mode (type fg %1 or fg %2) and press ^c to stop.

       You now have two wav format files. test1.wav is a 48KHz 16bit stereo file and test2.wav is a 8Khz 8bit Mono file.

       You can now playback the files as follows:

       o  ossplay -v test1.wav and it should show you that the file is indeed 48Khz 16bit stereo.

       o  ossplay -v test2.wav - you should see that this file is indeed a 8Khz 8bit mono file.

       What you have essentially accomplished is recording a single input stream into two different formats at the same time.

       You can now extend this analogy to record the input in mp3 format and RealAudio format simultaneously.

       The IMUX control panel can be displayed by typing ossxmix -d<imux mixer number> (for e.g. in the above example, IMUX mixer is #2 so we type
       ossxmix -d2

       There are record level control sliders for each input channel and it will show activity when a recording program is active on a	particular
       channel.

OPTIONS

       o  imux_masterdev:  Selects  which  physical device to use as the Master device for the IMUX driver.  Values: -1: automatically selected by
	  OSS, 1-N: Audio device index of the master device (as reported by ossinfo -a), Default: -1.

       o  imux_rate: Specifies what is the base sampling rate used by the imux driver.	Values: 5000-96000 Default: 48000

       o  imux_devices: Specifies number of Input Multiplexer devices to setup.  Values: 2-48 Default: 5

FILES

       /etc/oss4/conf/oss_imux.conf Device configuration file

AUTHOR

       4Front Technologies

								 16 December 2012						       oss_imux(7)