Synchronization studies in multimedia communications.

Abstract

Synchronization is considered as a key issue in distributed multimedia systems. Synchronization problems exist in both multimedia presentational and conversational applications. In a multimedia presentation, two basic synchronization issues are involved: Temporal Presentation Control (TPC) and Simultaneous Real-Time Data Delivery (SRTDD). TPC deals with the ordering of data objects in the presentation. SRTDD refers to simultaneously delivering multimedia data in different data streams belonging to the same time interval. In multimedia conversational applications, e.g., in cooperative applications, coordination control and causal ordering of the events give another synchronization problem. This thesis investigates the synchronization control in the distributed multimedia systems. All the above synchronization issues are covered. The temporal model and a synchronization algorithm for the TPC are proposed, which can support the real-time multimedia teleorchestration when multiple independent information sources are involved. The temporal model handles the relative and imprecise temporal requirements among the data objects in the "fuzzy" presentation scenario, and supports the synchronization dialogue among the independent sources. Thus the synchronization algorithm can be performed in a distributed manner. For the SRTDD control, an entire control architecture is presented which follows the layered communications model. We have introduced the multimedia session management, multimedia segment delivery, etc., to achieve the simultaneous data delivery. The Synchronization Quality of Service (SQoS) parameters are first applied for the SRTDD control over the ATM network. Meanwhile, taking the multimedia joint editing, one of the popular multimedia collaborative applications, as an example, we have developed the coordination control and the causal ordering algorithms for the joint editing session. Then in the second part of this thesis, we have studied the analytical performance modeling for distributed multimedia systems where the synchronization is considered. Stochastic Petri Nets (SPN) are applied to model the different multimedia synchronization systems. We developed a computational algorithm for a class of SPNs, i.e., the LBSPNs (Locally Balanced Stochastic Petri Nets), which have product form solutions. Applying the computational algorithm for LBSPN, the performance analysis of a joint editing system is conducted.