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

Other User documentation

User Guide to vat

vat is the visual audio tool developed by Van Jacobson and Steven McCanne (both of Lawrence Berkeley Laboratory, University of California, Berkeley, CA.) to provide audio teleconferencing over the Internet. This X11-based tool has gained from the attentions of other developers since its first appearance. It is the current standard audio tool for MICE conferencing.

What does it do for you?

Vat allows users to conduct one-to-one, one-to-many or many-to-many audio teleconferences. It provides a visual window by which the user can control his interaction with an audio conference or link to a single other user on the network.

While vat is used as an independent audio conferencing tool, it is frequently used as the audio part of a full videoconference. If you intend to use it in such a context, you are advised to review the Guide to Multi-media Conferencing.

The use of this tool for conferencing depends on the existence of a facility to multicast the sound from each participant to all others without having to broadcast it to every workstation on the network. This facility is known as the Multicast Backbone or Mbone.

To use vat you will need a workstation capable of receiving sound. For conferencing it must also be able to transmit sound. You will also need to install the correct version of the software for your workstation. You should use of the LBL Session Directory to publish and monitor network multicasts.

How do you use it?

The invocation may be from a command line or from the LBL Session Directory. There are many command-line parameters which are described in the vat manual pages.

The title of the conference is shown at the top, left of the vat window. This is set up using a command-line parameter (-C) when vat is invoked.

The window itself is divided into two parts: the right has controls for the local audio and the left has a status display of the hosts participating in the current conference.

Below the audio controls are three other buttons:

You can produce a log of all current part icipants by moving the mouse pointer into the window and typing L (upper case). The output is written to the window from which vat was invoked.

Important configuration options

Known Problems

The following are known problems with vat. If you know of any others please let us know. Poor audio quality when using the Sparc 5
SunOS 4.1.3U1
Sparc 5 audio still doesn't work properly but with SunOS 4.1.3U1 at least it works tolerably.

You need to apply the following patches: 102161-01 and 101508-07. Once you have done that I have found that setting the kernel variable audio_4231_bsize to 1200 will make the audio device work tolerably (you do hear a slight clicking sound about once per second if there is any playout time above a few hundred ms). To patch the kernel you need to:

    adb -k -w /vmunix /dev/mem
    audio_4231_bsize/W 0t1200   (to patch the running kernel)
    audio_4231_bsize?W 0t1200   (to patch kernel file on disk)

Graeme Wood, Scottish MICE National Support Centre (, November 1994

Solaris 2.3
As far as Solaris 2.3 is concerned, I do not think anything has changed recently. David Meyer at U. of Oregon ( has been pushing Sun on this front and he may have more information than I.

Graeme Wood, Scottish MICE National Support Centre (, November 1994

Solaris 2.4:
There is a small audio patch related to 'pops': 102037-01. I must say that for the most part our SS5 with Solaris 2.4 has very nice audio from vat *except* after any long-ish (technical term, that :-) ) pause it briefly (<3 sec) garbles the sound somewhat, but comes good again of it's own volition - no need to resize windows or jiggle sliders. I haven't had a chance to test other audio tools yet (xcdplayer and ShowMe).

Markus Buchhorn, Australian National University, Canberra (, February 1995

We would like to hear from you regarding your experiences in using this documentation. Comments of any kind and all technical enquiries should be addressed to


The development of wb, vat, and sd was supported by the Director, Office of Energy Research, Scientific Computing Staff, of the U.S. Depart ment of Energy under Contract No. DE-AC03-76SF00098.