An Isochronous Approach to Multimedia Synchronization in Distributed Environments

Abstract

In this chapter, we provide a new look at the synchronization issue in distributed environments. We attempt to explore the power of isochronous protocols, as advocated by Lamport, to the multimedia synchronization. It is based on the use of synchronized physical clock time instead of any form of logical clock or sequence numbers, and thus the clock synchronization across the distributed system is assumed. An isochronous protocol for achieving multimedia synchronization is presented. Derived from the globally synchronized clock, there exists a lattice structure in a system. Media conference participating processes in the system execute a simple clock-driven protocol, and all significant events (the sending and delivering of media data) are restricted to occur at lattice points of the globally synchronized space/time lattice. This lattice structure greatly simplifies the multimedia synchronization and readily maintains the temporal and causal relationship among the media. The basic simplicity of the approach makes it easier to understand the precise properties and behavior of a system. The availability of globally synchronized clock (for example, the new version of Internet NTP) and predictable quality of service of advanced communication networks make the isochronous synchronization approach not only attractive but also practical.