Provided by: oss4-base_4.2-build2005-2ubuntu1_i386 bug


       oss_imux - Input Muplexer audio driver.


       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
       format  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.


       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.


       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
       simplest 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:

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

       ·  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


       ·  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.

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

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


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


       4Front Technologies

                               05 February 2012                    oss_imux(7)