Lightweight Stream Synchronization Framework for Multimedia Collaborative Applications

The Internet and computer’s multimedia support have enabled geographically distributed multimedia applications. Today’s Internet best-effort services introduce unavoidable uncertainties in the data transfer delay and create the need for synchronization mechanisms that preserve the temporal relationship among streams. We present algorithms for stream synchronization that are immune to moderate clock drifting between sender and receivers and take into account the different time constraints of each media. In our time model we include delays outside the computer and network boundary, and we introduce the idea of virtual observer, which perceives the session as being in the same room with a sender. Specific media temporal requirements are fulfilled through a number of policies for delay management and special consideration is given to the time the algorithms take to reach steady state, which is crucial in interactive applications. We avoid the need for globally synchronized clocks for media synchronization by introducing the concept of user’s multimedia presence, which defines a new manner for combining streams coming from multiple sites. Finally, we implement and evaluate this framework with traces collected from the Internet.