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Evaluation of the Suitability of
Distributed Interactive Videoconferencing for use in Higher Education
4 Conclusions and future requirements
The quality of the video pictures was generally perceived as acceptable.
The variations in quality observed can be ascribed to a number of technical issues. These include the bandwidth of the connections (dragging of images, or ghosting), ATM cell loss (random pixel loss), and the image processing load on the workstations, particularly the Parallax video cards (slow speed of initial site linking). New video standards (such a MPEG ) will have a major impact on this latter problem.
The sound quality, although generally acceptable and noticeably better than in previous events, remains a recurring issue. Problems included echo, feedback, breaking up of the sound stream, and possible poor quality audio equipment at some sites (including poor volume level). Balancing the sound streams from the various sites was also a major problem, with some sites noticeably difficult to hear at times. In addition, synchronisation between audio and video was at times poor, and varied depending on the network status.
Although priority was given to transmission of the sound, there were numerous instances of sound degradation due to the video processing load. The audio is a critical part of the system. Although it is possible to 'get by' without video, it is not generally possible to continue without audio.
4.3 Network connections
The network on the whole was fairly reliable during the week, there were however two instances where failure of the network caused serious problems. In one instance all communications failed between Portugal and Spain for a whole afternoon, this caused serious problems as one of the lectures was based in Portugal and the programme consequently had to be rescheduled. Another serious problem was the ATM connections overheating in the afternoon caused network problems for those who entered the network via Paris.
4.4 System Stability
Instabilities in the system soon spread around the system and therefore there was a constant need for regular rebooting of all of the workstations at each of the sites. An attempt was made to do this during the breaks but at times it resulted in delays to the scheduled activities of up to 20 minutes.
Virtual Environments Visualisation