---
name: "oss_imux"
section: "7"
platform: "linux"
package: "oss4-base"
version: "4.2-build2010-2"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/oss_imux"
---

# oss\_imux(7)

Input Muplexer audio driver.

## 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**