efficient sub-stream encoding and transmission for p2p video on demand
TRANSCRIPT
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 1
Efficient Sub-Stream Encoding and Transmission for P2P Video on Demand
Zhengye LiuYanming Shen
Shivendra S. PanwarKeith W. Ross
Yao Wang
Polytechnic University, Brooklyn, NY, USA
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 2
Outline
• Motivation• P2P VoD system• Sub-stream encoding and transmission• Simulations• Conclusion
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 3
Motivation
• Video-on-demand services – Youtube, MSN video, google video,…– Content distribution networks (CDNs)
• P2P live streaming systems – PPLive, PPStream, UUSee, Coolstreaming,…– Support thousands of users simultaneously
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P2P VoD System
• Multiple video architecture– Extension of CDNs: Peers act as video servers– Contribute storage in addition to bandwidth– Help each other with stored videos
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Proposed System with Multiple Sub-Streams
In this illustration, two simultaneous streaming sessions are requested from nodes 4 and 5. The system initially selects nodes 2 and 3 to serve node 4’s request, and selects nodes 4 and 1 to serve node 5’s request. After Node 2 goes down, the system finds node 6 as a replacement
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 6
Benefit of Using Layered Coding/MDC
• Adaptive to the long-term bandwidth fluctuation due to peer churn– Uplink bandwidth fluctuation– Received video quality adapts to the available
uplink bandwidth• Robust to peer failure/disconnection
– One supplier failure only affects one/several sub-stream(s)
– Video quality will not be impaired seriously
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Multi-Stream Coding Schemes
(a) Layered coding (b) MDC
(c) Ideal scheme
– Compare schemes (a), (b) – Design (c)
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Push-Pull Delivery with Layered Coding
• Store all layers of a video• Push-pull for layer delivery
• Storage consumed for one video: RM
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The Ideal Scheme should consume minimum storage
• Can we reduce the consumed storage?
• The minimum storage: R+R/2+,…,+R/M≈ R ln(M)
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RS Coding
RS (8,2) coding for Layer 2
Any two received chunks can recover the original two chunks
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 11
RS Coding Instead of Replicating
RS (8,k) coding, k=1,2,3,4
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Redundancy-Free Transmission Based on Push-Pull Architecture
• A receiver schedules the chunks that should be delivered (Pull)• A supplier pushes the chunks based on the schedule (Push)
R
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Features of Proposed Scheme
• Ideal Scheme– Equal importance (like MDC)– Redundancy free transmission (like Layered coding)
• Minimum storage consumed– R ln(M) vs. RM
• M=4, 2.08R vs. 4R, save about 50%• M=32, 3.47R vs. 32R, save about 89%
• Since a peer needs to store fewer substreams: save server bandwidth
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand
Simulations
• Setting– 3000 peers, different uplink bandwidth– 30 videos, different popularity (Zipf distribution
with parameter 0.27)• Simulate two video sequences
– Foreman: low rate– Mobile: high rate
• Compare SLRS, Layered Coding, MD-FEC, RFMD• Performance metrics
– Discontinuity: number of undecodable GOPs/Total number of GOPs
– PSNR14
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand
Simulation Results
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Discontinuity of different schemes vs. number of active users under the “Foreman” sequence PSNR of different schemes
vs. number of active users under the “Foreman” sequence
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand
Simulation Results
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Discontinuity of different schemes vs. number of active users under the “Mobile” sequence
PSNR of different schemes vs. number of active users under the “Mobile” sequence
Efficient Sub-stream Encoding and Transmission for P2P Video on Demand 17
Conclusion
• Propose a redundancy-free transmission scheme based on a push-pull architecture
• RFMD– Advantages
• All substreams have equal importance: graceful quality degradation
• Only the source bits are transmitted: no transmission redundancy
• Coding instead replication: any combination of M or fewer substreams can be used in reconstructing video
– Additional cost:• Feedback from the client to each supplying peer: feasible
in typical P2P VoD applications