Interparticipant synchronization in real-time multimedia conferencing using feedback

An algorithm related to synchronization problems arising in a multimedia multiparty conference is presented in this paper. The proposed algorithm determines the set of packets generated periodically from different participants that are arriving at a node, either for mixing at the master of a conference, or for simply playing back at a regular participant of a conference. No global synchronization of the clocks is assumed. In this paper, the statistical approach rather than the deterministic is used to determine the proper set of packets that have to be mixed at a given time. The statistics are derived from the time stamp each packet carries along with it. The essence of the proposed algorithm is to estimate the expected packet arrival time (or reference time) for each participant. With the reference time at hand, the maximum jitter and the optimum waiting time for a mixer to wait packets from all participants can be determined. By employing feedback, the proposed algorithm is shown to lead to an optimum waiting/delay time. The error of the proposed algorithm is enumerated by the Chernoff bound, demonstrated by simulation, and shown to be acceptable in practical application.