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Scalable On-Demand Media Streaming with Packet Loss Recovery. A. Mahanti, D. L. Eager, (USask) M. K. Vernon, D S-Stukel (Wisc) Presented by Cheng Huang 04.08.2004. Introduction. VOD is cool, but might also be expensive Naïve implementation: connection per user
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Scalable On-Demand Media Streaming with Packet Loss Recovery A. Mahanti, D. L. Eager, (USask) M. K. Vernon, D S-Stukel (Wisc) Presented by Cheng Huang 04.08.2004
Introduction • VOD is cool, but might also be expensive • Naïve implementation: connection per user • Fortunately, users favor a few “hot” movies. • It is possible to have inexpensive approach to effectively share resources (server, network, etc.) and serve lots of requests. • Target of the on-demand streaming scheme • Scalable and reliable • Fundamental trade-offs • Server bandwidth (network bandwidth), startup delay and client bandwidth • Client buffer requirement (might be of less concern)
Outline • Periodic Broadcast Schemes • Bandwidth Skimming Scheme • Conclusion
Outline • Periodic Broadcast Schemes • Bandwidth Skimming Scheme • Conclusion
Pyramid Broadcast S. Viswanathan, T. Imielinski 1996
Skyscraper Broadcast K. A. Hua, S. Shen 1997
Optimized Periodic Broadcast A. Mahanti, D. L. Eager, M. K. Vernon, D. S.-Stukel 2001
Optimized Periodic Broadcast (cont.) • General segment length
Generalized OPB • Given the client reception bandwidth as constraint • b: maximum client reception bandwidth • r: bandwidth of each stream • s: number of streams client listen to concurrently • b = r*s
Loss Recovery Strategy • Digital Fountain approach • Use Error Correction Codes to generate n symbols from k original symbols (n >> k) • Symbol: frame, packet, etc. • Recover the k original symbols from any k out of n coded symbols
Generalized RPB • Reliable Periodic Broadcast (RPB) • Maximum tolerable loss rate p • need L/(1-p) packets in order to receive L packets • Segment length (a = 1/(1-p))
Outline • Periodic Broadcast Schemes • Bandwidth Skimming Scheme • Conclusion
Reliable Bandwidth Skimming • Pros • Bandwidth decreases as the client request rate decreases • VCR functionality – fast forward • Protocol • Primary stream is transmitted at rate 1 • Secondary stream is transmitted at rate p/(1-p) • Merging happens between primary streams, as well as secondary streams • Real system in Univ. of Wisconsin
Conclusions • Propose two reliable on-demand streaming schemes • RPB • RBS • Schemes investigate the fundamental trade-offs of on-demand streaming service