Multipoint Multimedia Teleconference System with Adaptive Synchronization

This paper discusses major issues involved in the design and implementation of a multipoint multimedia conference system, such as system architecture, conference management, session control, and intramedium and intermedia synchronization. In particular, emphasis is given to conference management and adaptive synchronization algorithms. The management of multiparticipants is based upon a distributed architecture for greater flexibility. The proposed synchronization algorithm is adaptive to network changes, eliminates the need for a global clock, and is immune to the clock frequency drift, while its realization is very simple and the involved overhead is minimal. The essence of the algorithm is partitioning the vicinity of the arrival epochs of multimedia objects into three regions and counting arrivals at each region. The function of the synchronizer is to shift the playback clock (PBC) according to the individual counter contents. The ideas proposed are implemented within a teleconference system on the Ethernet/FDDI using the TCP/UDP. Experimental results show that the proposed synchronization algorithm performs well in our network testbed environment.