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Chapter 1


At present, most videoconferencing must take place between participants who are each using the same videoconferencing software package since packages from different vendors tend to use their own proprietary compression schemes and control protocols. This may be acceptable for internal organisational communication where a de facto standard hardware/software policy has been adopted but is obviously fairly prohibitive where different organisations, possibly in different countries, or participants on different platforms, wish to conference.

The answer is, of course, an international standard for videoconferencing communication. The relevant standard in this area, which is currently being adopted by the computer industry, is called H.320. It is a ITU-T (International Telecommunications Union - Telecommunications Standards Section), formerly CCITT, standard which encompasses several subsidiary standards for: communications protocol (H.242), audio/video synchronisation (H.221), video compression (H261) and audio (G.728, G.722, G.711) transmissions. The H.261 standard was developed to work over Px64 digital channels (64 Kbits/sec to 2.048 Megabits/sec). H.320 also includes standards to handle multi-way conferencing with ISDN (H.231 and H.243) and will also eventually include a standard covering document sharing or whiteboard (T.120).

H320 is a relatively recent development and products which support it are only just beginning to appear. In fact, at the time of writing, we have seen several glossy brochures claiming support for it, but we have not seen a delivered product. If other new standards are anything to go by it is probably premature to assume that H320 will provide a short-term answer to cross-product and cross-platform videoconferencing.

In fact vendors have been developing their own 'standards' and it is possible that one or more of these could develop into a de facto standard if one of these vendors begins to dominate the market. CELLB for video compression from SUN and Indeo from Intel are two such candidates. We found in our study that video performance using Showme which uses CELLB was noticeably better than that using the public domain item IVS which uses H261. This may be an indication that the H320 group of standards could become outdated quickly and will increase the likelihood that a dominant vendors product (likely to be in the Windows market) will become a de facto standard.

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