Prototyping distributed multimedia systems using communicating real-time state machines

The paper describes a methodology for the development of real time systems and shows its application to the modeling, analysis and implementation of distributed multimedia systems. The methodology is centered on Communicating Real-Time State Machines as the modeling language and is supported by jCRSM, a Java2 based toolset. The latter provides a graphical environment for editing, testing, debugging and Java code generation of a prototyped system. Multimedia systems are particular real time systems which normally do not have hard deadlines to fulfill but only soft deadlines concerning the achievement of a user-defined level of quality of service. For instance, timing QoS parameters refer to jitter, skew and end-to-end delay, which are to be kept bounded throughout a multimedia session. QoS constraints are monitored by assertions on the recorded timestamped event histories. The paper reports some experimental results of a modeled remote multimedia presentation system.