January 1996

Document Type


Degree Name



Dept. of Computer Science and Engineering


Oregon Graduate Institute of Science & Technology


Digital multimedia systems are rapidly becoming ubiquitous with nearly all computer platforms offering support for audio and video. Multimedia computing promises to augment or replace most of the traditional broadcast and print media with more interactive and personalized information services. Unfortunately, today's real-time multimedia services are either tailored to a personal computer environment or are vulnerable to performance degradations in a shared environment. Designers are faced with two fundamental problems : choosing a digital representation for continuous media, and scheduling resources to approximate a real-time presentation. While some multimedia systems take an ad hoc approach to these problems, an optimal solution requires a complete specification of presentation quality requirements. This thesis offers the first complete framework for specifying presentation Quality of Service (QOS) requirements. Beginning with a formal definition of an ideal presentation, the thesis describes a quality estimation function based on error in the presentation outputs. This approach allows device and data independent descriptions of multimedia services. We provide a detailed example of a formal QOS specification composed of orthogonal content, view, and quality descriptors. These descriptors are designed to support useful, complex multimedia presentations and to have a simple formal semantics. The practicality of the QOS specifications is demonstrated by a multimedia player that translates QOS requirements at runtime into acceptable presentations with near-optimal resource use.





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