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Multimedia Information System Lab. Network Architecture Res. Group Cooperative Video Streaming Mechanisms with Video Quality Adjustment Naoki Wakamiya Osaka University, Japan Slide 2 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya2 Video streaming system with proxies To provide low-delay and high-quality streaming service Slide 3 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya3 Issues Segmentation of video streams Video quality adjustment Locating the appropriate server Cache management Prefetching Slide 4 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya4 Protocols Each system entity communicates with each other Slide 5 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya5 Video block transfer Video Server Neighboring Proxy Proxy Cache Server Client PLAY message with QoS Cache Hit 1.Read block from cache 2.Quality adjustment Play out Initial buffering1/fps Prefetching 1.Check cache 2.Request block transfer 3.Cache Cache Miss 1.Determine helper server 2.Request block transfer 3.Quality adjustment & cache Freeze time Slide 6 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya6 Cache table Cache table is used to maintain information of locally cached blocks block number quality of cached block marker Marker is used to imply the possibility that the block will be required by the other proxies Range of marking is limited by inquiry window QUERY and REPLY messages are exchanged to update markers Slide 7 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya7 Remote table Remote table is used to maintain information of blocks cached at the other servers (video server, proxies) estimated one way delay estimated throughput quality of offerable block Delay and throughput are estimated using measurement tools or TCP-friendly control mechanisms QUERY and REPLY messages are exchanged to update remote tables Slide 8 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya8 Block retrieval algorithm the proxy determines the quality of block to offer to client based on request cache and remote tables estimations, the number of blocks in the clients prefetch buffer parameter If the quality of block offerable using cache satisfies, it is regarded as cache hit Slide 9 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya9 Block prefetching algorithm The proxy retrieves the block preparing for the future cache miss high quality med quality low quality uncached case 1 case 2 block number request Prefetching Window prefetch Slide 10 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya10 Cache replacement algorithm Some blocks might be replaced with a newly retrieved block startend Inquiry window client 1 Inquiry window Inquiry window client 2 marker Quality adjustment Removal victim Slide 11 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya11 Evaluation Measurements average freeze time required buffer size degree of satisfaction ratio of provided quality to requested quality 1 sec block P=10, I=20 initial wait 4 sec parameter 35 Gbit buffer Slide 12 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya12 Comparison Four mechanisms are compared 0.001 0.01 0.1 1 10 100 12345678910 Average Freeze Time [sec] Client Independent w/o Prefetch Independent c/w Prefetch Cooperative w/o Prefetch Cooperative c/w Prefetch 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 12345678910 Quality ratio Client Independent w/o Prefetch Independent c/w Prefetch Cooperative w/o Prefetch Cooperative c/w Prefetch Slide 13 Multimedia Information System Lab. Network Architecture Res. Group 2001/11/07N. Wakamiya13 Conclusion The low-delay and high-quality video streaming service is accomplished Further efficient control is required We have to consider implementation issues