Simulation of Multimedia Systems based on Actors and QoSsynchronizers

This paper describes a variant of the actor model suited to the development of multimedia systems. The actor model centers on non-overkilling concurrency and customizable constraint-directed scheduling. A distributed multimedia system consists of a collection of actors interacting to one another to fulfil a common goal, e.g., interactive videoconference, video recording on-demand, etc. Timing synchronization rests on reflective actors (QoSsynchronizers) which filter actor messages and schedule them according to applicationdependent QoS parameters. Requirements of a multimedia system can be formalized by Time Stream Petri Nets. In order to support QoS constraints analysis and validation, media actors are then prototyped under simulation by exploiting a flexibility of the adopted actor model to operate transparently under real or virtual time. The transition from the modeling, to analysis, down through to the implementation stages is therefore seamless. The paper describes the application of the methodology to the development of a lip-sync filter for live or on-demand multimedia sessions and reports some collected experimental results

A Methodology Centered on Modularization of QoS Constraints for the Development and Performance Evaluation of Multimedia Systems

This paper proposes a methodology for the development of multimedia systems. It is based on a time-sensitive, reflective actor framework that centers on lightweight actors, nonoverkilling concurrency and customizable constraint-directed scheduling. A multimedia system can be visualized as a collection of media actors, i.e., autonomous, concurrent and computational processing entities, involved in multimedia sessions. QoS requirements associated to a multimedia session are incorporated in reflective actors called QoSsynchronizers that manage and enforce application-dependent QoS parameters. Timing QoS parameters are first specified by using Time Stream Petri Nets and then translated in terms of a QoSsynchronizer. In order to support QoS constraints analysis and validation, media actors and QoSsynchronizers are prototyped under simulation by exploiting a flexibility of the adopted framework to operate transparently under virtual or real time. Thus a seamless transition from the modeling to the implementation stages can be obtained. The paper describes the use of the methodology for the development of live and ondemand multimedia applications