Multimedia Conferencing

The fundamental change in telecommunications brought about by the increase in computer power and the emergence of viable multimedia technologies has had a major impact.

Conferencing has applications in a variety of fields including collaborative learning, distributed (global) tele-conferencing, general video Conferencing, groupware (See Section 26.3 below) etc.

Multimedia Conferencing may be defined as :

• Pure teleconferencing + cooperative work supported by computer

The following requirements are necessary for a Multimedia Conferencing:

• Multipoint facility -- many connections over a network
• Personalization -- customisation of the environment to suit user needs and to identify users on systems
• Unification of teleconference facilities with existing office automation facilities
• User-friendly interfaces for displaying documents and facial images

The typical media ingredients of a multimedia conference, as part of computer supported cooperative work, include audio, video, and perhaps a shared whiteboard or similar. These media each need specific treatment:

• The intelligibility of digitised audio is very sensitive to missing samples and playout jitter. A bandwidth share of 64 kbps is necessary for the uncompressed transmission of one audio source at telephone quality. Compression mechanism can further reduce the data rate. In any case, the bandwidth demand is small compared to the capacities of current LANs, whereas packet loss due to congestion occurs often over the Internet.
• Video generated by a typical computer-mounted camera is less sensitive to loss and jitter than audio, but the data rate even of compressed video is much higher than the audio data rate.
• Because audio and video conferences are real-time interactive applications, a low transmission latency is required for both media; the low-latency requirement further implies that buffering cannot be used in larger scale to compensate for transmission jitter, as could be done on the receiving end of video-on-demand systems.
• Compared to the other two media, whiteboard applications generate very little traffic. Their real-time demands, concerning delay, latency or jitter, are also comparably low. However, the reliable transmission of every single event is absolutely necessary to give each participant an identical, consistent view of the virtual board. Microsoft's Netmeeting
  http://www.microsoft.com/netmeeting/ is a simple example of this approach.

Examples systems include:

• NEC's MERMAID
• Fujitsu's THE MONSTER
• Hitachi's THE PERSONAL MULTIMEDIA TELLECONFERENCING TERMINAL
• BELL CORE's CRUISER
• Olivetti's VOX
• MIT's Project Athena's Galatea
• Xerox Parc's Etherphone