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  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.

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 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 channel.

OPTIONS

       •  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

FILES

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

AUTHOR

       4Front Technologies

                                                13 November 2019                                     oss_imux(7)