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vat - LBNL Audio Conferencing Tool

Vat is an audio conferencing application developed by theNetwork Research GroupofLawrence Berkeley National Laboratory.Source code and pre-compiled binaries are available viaanonymous ftp.Vat-related questions and feedback are welcome and can be sentto the developers viavat@ee.lbl.gov.

Contents

Other links:

Overview

The LBNL audio tool,vat, is a real-time, multi-party,multimedia applicationfor audio conferencing over the Internet. Vat is based on the Draft Internet StandardReal-time Transport Protocol (RTP) developed by the IETFAudio/Video Transport working group.RTP is an application-level protocol implemented entirely withinvat -- you need no special system enhancements to run RTP. Althoughvat can be run point-to-point using standard unicast IP addresses,it is primarily intended as a multiparty conferencing application.To make use of the conferencing capabilities, your system must supportIP Multicast, and ideally, your network should be connected to theIP Multicast Backbone (MBone).

Vat provides only the audio portion of a multimedia conference;video, whiteboard, and session control tools are implemented as separateapplications. Our video tool is calledvic andour whiteboard toolwb,UCL developed the session directory toolsdr Other related applications include ISI's Multimedia Conference Control,mmcc,the Xerox PARC Network Video tool,nvand the INRIA Video-conferencing System,ivs.

Installation

The easiest way to install vat is to grab the binary distributionfor your architecture (see the list below), unpack it, andinstall the executable and manual entry. You can also getthe source distribution andbuild vat from source.

Supported Systems

Note: these links will not be valid until the official 4.0 release.
Sparcs running SunOS
Vat should run on any version of sparcstation (1, 2, 4, 5, 10, 20,SLC, ELC, IPC, IPX) running SunOS 4.1.x.

Note that theaudio buffer size used by the stock SunOS 4.1.x kernelis too large for good interactive response. This canbe fixed with a kernel patch -- instructions are intheMBone FAQ.

Sparcs running Solaris
Vat should run on any version of sparcstation (1, 2, 4, 5, 10, 20,SLC, ELC, IPC, IPX) running Solaris 2.x for x>1.

Vat does not work in unicast mode under Solaris 2.3 due toa kernel bug. Sun has provided aworkaround.

DEC OSF-3.xandDEC Ultrix
Vat should run on any DEC Alpha running OSF/1 v3.x usingeither the build-in audio or the audio on a J300 board.Vat should run on any DEC 3max (5000 series) with a LoFiaudio board and running Ultrix 4.2 or above.On these architectures, vat requires release 3 of the DEC CRLAudioFileaudio server.

HP HPUX-9
Vat may run on versions of HP Snake (700 or 7000 series)that have built-in audio hardware. We have tested it on710s, 715s & 735s.

Note that the HPUX Audio server (AServer) wasnotdesigned with interactive audio in mind -- in our attemptsto use it, we typically saw delays of several seconds between theaudio hardware and the net. To work around problems withAServer, vat uses the kernel /dev/audio device directly.Unfortunately, this interface is not documented and HPhas changed it several times.Our only HP is an ancient 735 running HPUX-9.0 so we rely on othersin the user community to send us the patches or informationneeded to keep vat running on HP hardware.

SGI Irix-5
Should run on any SGI Indy, Indigo or Indigo2 running IRIX 5.x.We have tested it on an Indigo and an Indy.

x86 BSD/OS 2
Vat should run on i386/486/586 PCs with soundblaster-compatiblesound cards running BSD/386 2.0 or later.

The i386 binary also has been reported to run under NetBSD(using a modified version of the LBL sound driver) andFreeBSD (using the Linux sound driver with additionalsupport for /dev/audio). Amancio Hasty (hasty@netcom.com)reports that under FreeBSD vat can operate in full-duplexmode with the Gravis Ultrasound (and that the quality isvery satisfactory).

x86 Linux
Vat should run on i386/486/586 PCs with equiped with sound cardssupported byVoxWare(the standard Linux sound driver) and running Linux 1.2.8 or later.

The current vat linux audio driver is quite primitive. Ittreats the sound card as half-duplex (e.g., a soundblaster)even if it is capable of full-duplex operation (e.g., a GUS).It also does not use the `mixer' controls that set the recordand play volume and/or select input and output ports. We hopesomeone in the community will add the missing pieces tovat's linux-audio.cc.

Under linux 1.2.x, multicast through the loopback interfacedoes not work.This is a serious deficiency since local(loopback) multicast sockets are used to implement"conference busses" that vat/vic/etc. use to do thingslike pass the audio hardware between different vats,automatically switch video windows on audio activity, etc.We understand that this problem has been fixed in morerecent versions of linux (1.3.?). If your kernel doesn'thave the fix, the first symptom is that it will be verydifficult to switch the audio between multiple instancesof vat. (Normally you just click the right mouse button itthe vat window you want active and the audio will be assignedto that window. This won't work at all if the linux loopbackmulticast is broken.) If your kernel has the bug, it willbe difficult to handle multiple vats and you will probably wantto run just one at a time.

Binaries Maintained by Other Sites
Several other systems are supported but we don't have theresources to build and maintain binries. These other sites havekindly offered their help.
AIX
AIX binaries provided byAndrew Booker andKira Attwood.
FreeBSD
Amancio Hasty has madeFreeBSD binaries for many of the MBone tools publicly available.
SCO Unix
Shawn McMurdo ported vat to SCO UNix. Somenotesanda binary distributionare publicly available from their ftp server.

Building Vat from Source

To build vat from source, start by getting and unpacking thesource tar. E.g., after ftping the tar, run(gzip is availablefrom the GNU Project.)This will place the contents of the source distributionin./vat-x.y wherex.y is the current version number.`cd' into this directory and do the following:If you are attempting to get vat running on a platform that isn'tlisted above, things will probably be more difficult.See theporting notes for help.

If you do a port to a new system or hardware and would liketo feed your changes back into the distribution, we would bedelighted to have them. If you have a vat binary you would like addedthe the distribution, or if you would like us to add a link tothis page, please let us know.

Building Vat under Windows

We use Microsoft's Visual C++ 4.x to compile vat under Windows.Our build environment is essentially the same as that in the Tcl/Tk release.There's amakefile.vc in the source distributionand you can simply run nmake from a dos shell:You might have to fix up the tcl, tk and gsm paths in makefile.vc (themakefile assumes these are all in ".." relative to the vat srcdirectory and that they've all been built before you build vat).If you want to build vat from the workshop, follow thedirections in thetk windows faq for using makefile.vc to createa makefile project.

Notes

Acknowledgments

Funding for this work was provided by theOffice of Energy Research, Mathematical, Information, and ComputationalSciences Division, of the U.S. Department of Energy underContract No. DE-AC03-76SF00098.Equipment grants and support were provided by Sun Microsystems,Digital Equipment Corporation, and Silicon Graphics Inc.

Feedback

As always, we very much want to hear about bugs and problems. Pleasedon't hesitate to offer suggestions or other feedback. Send all vatrelated correspondence tovat@ee.lbl.gov(this list includes only the developers and is not distributed beyondour site).

Van Jacobson(van@ee.lbl.gov)
Steven McCanne(mccanne@ee.lbl.gov)

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