A Multimedia Server on the Spring Real-Time System

An integrated platform which is capable of meeting requirements of both traditional real-time control processing and multimedia processing has enormous potential for accommodating various kinds of new applications. However, few, if any, research or commercial systems successfully provide architectural and OS mechanisms which can efficiently support both deterministic hard real-time computation and less deterministic multimedia soft real-time computation. In this paper, we propose a multimedia server executing on the Spring real-time system to provide different classes of guarantee to support both types of processing. Using a planning based scheduler, the Spring system is a multiprocessor real-time system which was developed to satisfy the requirements of deterministic guarantees for hard real-time tasks. Adding a multimedia server enables Spring to also support multiple periodic multimedia streams with a capability for QOS graceful degradation of the multimedia streams during system overload. In this paper we address realistic system implementation issues and develop multimedia server scheduling algorithms. Our performance evaluation demonstrates both that a multimedia server algorithm based on a flexible, proportional allocation scheme provides the best performance and that simple iterative scheduling is adequate to handle graceful degradation of the multimedia streams.