Video Multicast over the Internet

1. Video Multicast over the Internet Bell Lab. And Georgia Institute of Technologies IEEE Network · March/April 1999 Presented by: Liang-Yuh Wu Lung-Yuan Wu Hao-Hsiang Ku 12 / 6 / 2001

2. Agenda 1. Abstract 2. Basic idea 3. Single-stream video multicast 4. Replicated-stream video multicast 5. Layered video multicast 6. Replicated vs. Layered 7. Error Control 8. Concluding Remarks

3. Abstract Why? • Multicast of video / future network service Video Conference Distance Learning Remote Presentation Media-on-Demand ( MOD,VOD ) • Lacks support for QoS assurance • Heterogeneity of the Internet transmission  Problem of “ Real time & Bandwidth”

4. Focus & Discussion ?? Base requires for Multicast video : • Mechanisms for Multicast data delivery • Ability to accommodate Real-time video Focus on: • 1.How real-time video can be accommodated over Internet 2.Fairness

5. Some general approaches and issue (Real-time): ---Delay jitter, Data loss 1. Using QoS reserve resources 2. Using adaptive rate control “ Feedback mechanism ” 3.Buffering 4.Change compression parameters 5.Error control technology

6. Basic idea • Video Bit-Rate adaptation • Adaptive Bit-Rate Video Multicast Options 1. Single Stream Adaptive Approach 2. Replicated Adaptive Streams Approach 3. Layered Video Streams Approach

7. Single-stream Video Multicast • The IVS Approach (in the H.261 encoder) • Feedback information is based on packet loss measured at the receiver • Packet loss is detected using RTP (Real-time Transport Control) • RTP sends “reception reports” that provide feedback information

8. Single-stream Video Multicast(cont.) • Feedback implosion problem • Probabilistic multicast technique • Probing mechanism • Can’t provide fair treatment to multiple receiver in a heterogeneous environment • Tradeoff between multicast and unicast

10. Replicated-Stream Video Multicast • The DSG (Destination Set Grouping) Protocol • The goal of the DSG: • To improve fairness over a single-group feedback-controlled video multicast • To address “scalability” • By transmitting video of differing quality and differing data rate on different multicast channels and allowing receivers to select the most appropriate one.

12. Replicated-Stream Video Multicast(cont.) • The DSG protocol has two main Components: • Intra-stream protocol • Inter-stream change protocol • A DSG experiment result : • Fairness among receiver is improved significantly over a single-group approach while incurring only a small additional bandwidth overhead.

14. Layered Video Multicast • Video layering can be supported by many video compression techniques • EX: MPEG-2 supports layered encoding by defining four scalable modes • Layered Video Multicast Protocol • Receiver-driven Layered Multicast (RLM) • Hierarchical Rate control (HRC)

16. Receiver-driven Layered Multicast • Receiver-based control • Advantage: • burden of adaptation is moved from the sender to the receiver • Join-experiment • result is successful • result is failed

17. Receiver-driven Layered Multicast(cont.) • The key to scalability in layered multicast is “adding or dropping a layer” • Shared Learning • Advantage: • Disadvantage: • unnecessary bandwidth and message processing overhead • Too much state information

18. Hierarchical Rate control (HRC) • Layered Video Multicast with retransmissions (LVMR) • two key contributions: • retransmitting lost packets • adapting to network congestion and heterogeneity using HRC • Hierarchical Rate control (HRC) • to distribute the information between the sender, receivers, and some agents • each entity maintains only the information relevant to itself

19. Hierarchical Rate control (HRC)(cont.) • Comparing with RLM: • allow receiver to maintain minimal state information • decrease control traffic on the multicast session • multiple experiments to be conducted simultaneously • drop the correct layer(s) during congestion in most case

20. Hierarchical Rate control (HRC)(cont.) • In addition to avoid the above drawback of RLM • Comprehensive group knowledge base • Collaborative layer drop • decrease layer oscillation • achieves more effective rate adaptation • maintains better video reception quality • Add-layer experiment • decrease unnecessary add-layer experiment • provide smoother video quality

21. Replicated-stream VS. Layered video • For video multicast, layering is determined more by the coding requirements than by the bandwidth requirements • Replicated-stream VS Layered video: • bandwidth economy • Processing overhead

22. Error Control 1.Layered Video Multicast with Retransmission (LVMR) 2.Structure-Oriented Resilient Multicast (STORM) 3.Client-Server Architecture

23. The Key Idea In LVMR • Use a statically configured logical tree • Set Designated Receivers (DRs) at each level • Improve efficiency by no asking for retransmission • Improve response time by sending immediate message and multicast retransmissions • Use Buffers • Combine retransmission mechanisms

26. The Key Idea In STROM • Each receiver to dynamically select the best possible DR • Use a dynamically logical tree • Receiver decide the latency or reliability

27. The Steps of STORM • 1.Build the recovery structure • 2.Selection of Parent Nodes • 3.Adapting the structure

28. The Key Idea In Client-Server Architecture • Separate the actual senders and receivers. • Receiver either get the original or repaired video stream. • The retransmit server and the repair server can be organized into LVMR • Using RTP • Repair Buffer

30. Concluding Remarks • Network congestion lead to degrade the video quality. • Non-adaptive streams of video data don not share resource well in a best-effort network.

31. Future Work • To build a mechanisms which provide for the co-existence and resource sharing of video multicast stream . • Formalization of the notion of fairness • Understanding the effect of pricing on the behavior of receiver in a multicast video environment.

32. The End Thank you so much!!