A Tuning System for Distributed Multimedia Applications

Distributed multimedia applications such as Video-On-Demand (VOD) will need user-friendly graphical interfaces to specify and control compressed continuous media and their service behavior according to the quality perceived by the human user. This requires a new extension of the Quality of Service (QoS) concept to incorporate the perceptual quality. In this paper, we investigate services for supporting perceptual quality and propose a user-friendly and robust tuning system. Our tuning system extends adaptive and tuning services currently used at the application subsystem level and it enables the speciication, monitoring and user-controlled adaptation of perceptual QoS. Furthermore, all services in the tuning system have the goal of (1) modularity so that they can be plugged and played in a distributed multimedia application, and (2) graceful degradation of perceptual QoS. The paper discusses in detail the QoS concepts, services and protocols, which are the basis of our tuning system design and implementation, and architectural issues. Two algorithms are presented: the Probe-based Algorithm used at the beginning of the call set up phase for QoS speciication, and the Adaptation Algorithm used to adjust to user-speciied parameter changes while taking into account dynamics and non-determinism caused by the OS and underlying network protocols. Our experimental results show the eeectiveness of the probe and adaptation mechanisms, good results for perceptual QoS provision, fast response to user requests, and the feasibility of our services to accommodate user speciied changes with respect to non-deterministic behavior of underlying system.