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Layer-Encoded Video in Scalable Adaptive Streaming. Michael Zink, Jens Schmitt, and Ralf Steinmetz , Fellow, IEEE IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, FEBRUARY 2005. Outline. What is scalable adaptive streaming? Maximize the quality of the cached video
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Layer-Encoded Video in Scalable Adaptive Streaming Michael Zink, Jens Schmitt, and Ralf Steinmetz, Fellow, IEEE IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, FEBRUARY 2005
Outline • What is scalable adaptive streaming? • Maximize the quality of the cached video • Average PSNR is not a good assessment • Subjective impression of variations in layer-encoded video • Retransmission scheduling • Simulation results • Conclusion
What is scalable adaptive streaming • Main goal: • Provide a true video-on-demand (TVoD) system • Issues: • Quality Adaptation (congestion control) • Layer-encoded technique • Scalability (performance) • Proxy caching
How to assess the quality of video • Use a subjective assessment • The experiment was performed with 94 test candidates • (62 males and 32 females), between the age of 14 and 64. • Video: • Consists of 4 layers • The size of the nth layer: sn = 2sn-1
Subjective assessment v.s PSNR (1/2) • Six variations in layer-encoded video • Farm1–Amplitude: • Decrease slightly has better quality • Farm2–Frequency: • Lesser layer changes has higher quality
Subjective assessment v.s PSNR (1/2) • M&C1–Closing the Gap: • Close a gap in a lower layer has higher quality • M&C2–Constancy: • No layer changes has better quality
Subjective assessment v.s PSNR (2/2) • M&C3–Constancy at a Higher Level: • Tennis1–All is Well That Ends Well: • Increasing the amount of layers in the end leads to a higher quality
Compare Subject and PSNR quality • Subject assessment is more precise than PSNR. • s(v) represents the same result as subject assessment. • Minimize the frequency and amplitude will have the better quality (reducing the layer variations).
When to schedule the retransmissions • Retransmission time: • Directly after the initial streaming process • During subsequent requests • During requests for different content from the server
layers frames How to schedule the retransmissions • Scheduling goals: • Decreasing quality variations for a cached video is important. • Minimize both frequency of variations and amplitude of variations. s(v): spectrum
Algorithms for retransmission scheduling (1/3) • Optimal retransmission scheduling • is a discrete nonlinear stochastic optimization problem (NP-complete) • Heuristics for retransmission scheduling • Unrestricted priority-based heuristics • Send periodic retransmission requests to the server to ensure that the server obtains an up-to-date schedule of retransmissions.
Algorithms for retransmission scheduling (2/3) • Three heuristics of unrestricted priority-based retransmission scheduling algorithm: • Case1 : Unrestricted lowest layer first (U-LLF)
Algorithms for retransmission scheduling (3/3) • Case2 : Unrestricted shortest gap lowest layer first (U-SG-LLF) • Case3 : Unrestricted lowest layer shortest gap first (U-LL-SGF)
Conclusion • Promise a scalable TCP-friendly TVoD system • Scalable adaptive system • Use both caching and layer-encoded • Develop the retransmission algorithms to retransmit missing segments • Minimize the frequency and amplitude of the variations of the cached video