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Workstations

There are currently three software video conferencing systems in frequent use in the internet - these are IVS from INRIA (a MICE partner) NV from Xerox Parc [2], and CU-See-Me from Cornell University. It can also be safely assumed that many workstation manufacturers have their own systems under development (such as the Cell-B video compression system from Sun Microsystems). Of these, IVS is currently the only system to conform to international standards (in this case H.261, which allows it to interwork with hardware codecs). IVS and NV are tailored to work over IP multicast, which means that they can be deployed in a multiway conference without the need for a central multi-point hub. However, in a large conference, if many sites have video transmission capabilities, then clearly both the receiving workstations and the networks themselves will become overloaded if every site multicasts to all others without some form of coordination. There is no such problem with audio, as typically only one person will be speaking at once.

We also expect to accommodate workstations with reduced functionality which operate only with audio, or in which the video function is restricted to document entry and display. For this functionality, it may not be necessary even to include the camera/frame grabber, though some form of local scanner (e.g. a facsimile device interfaced to the workstation) would be helpful.

A diagram is given in Fig. 3. The MICE partners use their existing workstations, and their audio/video software is largely derived from INRIA's IVS. INRIA and Stuttgart University have the responsibility of providing a reference installation which could be copied by organisations not having their own facilities but wishing to join the programme.