This documentation is a revised edition of the
MICE documentation of
National Support Centre London
Revision by Jens Elkner (

Other User documentation

Important configuration options for vat

Multiple vat sessions.

One host can be running an arbitrary number of vat sessions (presumably with different destination addresses). Since most workstations have only one set of audio hardware, only one of those sessions will be able to access the mike and speaker. For the most part, the vat sessions will automatically follow the action. If you unmute the mike or press the Keep button, the audio device will be acquired by that session and the session that previously held the audio will relinquish it. Vat displays the title bar in an oblique font when the audio is not being held.

A vat session will also acquire the audio if there is input from the network, so, to prevent a background vat session from taking the audio from the foreground session, you can toggle the Keep button. When the Keep button is highlighted, vat will reliquish the audio only when you unmute the mike or select the Keep button in another window. The audio can be explicitly released by clicking on the Release button.

You should not run multiple vat windows when running as a mixer for some other site. This is because the audio hardware is needed to provide the timing for the mixing function; the window doing the mixing will cease to function if it loses control of the audio hardware.

Using vat as a mixer.

This function allows vat to function as a gateway. It has three uses:
Bandwidth Adaptation
If you want to participate in a conference at work that is using 64Kb/s PCM but you to join over the 9.6Kb/s line to your home, you can set up a machine at work as a proxy for your machine at home.
If a conference has two communities connected by a low speed link, it is desirable to mix multiple conversations into a single data stream rather than transmitting each separately.
Format Conversion
Where two separate conference environments need to interact, they can agree on an interface format and this will only affect the two peers who are communicating between the two environments.
Details of this facility are given in the vat manual page.