A Framework for Scheduling Soft Real-time Multimedia Applications

A. Kassler, B. Reiterer, and J. Kaiser (Germany)


CPU Scheduling, Quality of Service, Multimedia


Distributed multimedia applications have scheduling require ments which substantially differ from those in hard real-time sys tems. The system load in a multimedia system is widely varying and scheduling schemes based on the worst-case execution time assumption are infeasible from the costs point of view. Although QoS requirements strongly demand that deadlines are not missed, this point can be treated in a probabilistic way in contrast to the hard real-time safety critical field. As a consequence, problems of transient overload occur and have to be an intrinsic element of a scheduling scheme. Flexible mechanisms to monitor the system and to adapt to changing load requirements have to be incorpo rated. This paper presents a general architectural framework to schedule soft real-time multimedia tasks and guarantee a negoti ated amount of processor share in the presence of competing ap plications. It comprises the necessary components for admittance test, resource controlling and on-line system monitoring which form the basis for an adaptive scheduling approach. We provide preliminary results and analyze different adaptation policies for multiple adaptive threads in our Windows NT implementation.

Important Links:

Go Back