Architectures and algorithms for digital multimedia on-demand servers

Abstract

Future advances in networking coupled with the rapid advances in storage technologies will make it feasible to build multimedia on-demand servers that provide services similar to those of neighborhood videotape rental stores on a metropolitan-area network. A critical requirement in building a multimedia server is the need for guaranteeing continuous playback of media streams. Hence, there are two important questions that need to be addressed in designing a multimedia server: (1) how should media streams be laid out on disk so as to guarantee their continuous retrieval, and (2) how can multiple clients be serviced simultaneously by a multimedia server? In order to address the first question, we propose a constrained block placement policy, in which separations between successive media blocks on disk are bounded so as to guarantee their continuous retrieval at real-time rates. To enable the multimedia server to support multiple clients, we study various policies (such as, round robin and quality proportional) for servicing multiple clients, and propose admission control algorithms for determining whether a new client can be admitted without violating the real-time requirements of any of the clients already being serviced. Finally, we capture the multiplicity of media streams characterizing multimedia objects by defining a multimedia rope abstraction, and describe techniques for their efficient storage on disk, as well as address the problem of servicing multiple rope retrieval requests simultaneously.