Video communication on LANs-multimedia CSCW applications

In the framework of our research on CSCW (computer supported cooperative work) support tools, a prototype was developed for a digital desktop videoconference system using an Ethernet network under “Windows for Workgroups” from Microsoft. It offers a cost-effective platform to study the dynamics of video communication in a CSCW environment, as neither network protocols´ modifications nor expensive hardware updates are needed with present LAN installations. Based on the “agent” concept, the system software design is entirely object-oriented. Gaps and jitters are observed during full-motion video display due to the packet transfer mode of LANs and the excessive delays in the related transmission and reception processes. Working directly with a simplified protocol at the network´s transport layer (NetBIOS), we maximize the use of the network bandwidth, thus the data fragmentation and the overheads in the higher layers of the network software can be avoided. By fine tuning the relevant parameters such as the size and the resolution of the captured video images as well as the buffer sizes and the dispatch rates, continuous and synchronized video/audio display can be obtained