1. Adaptive MPEG-4 Video Streaming with Bandwidth Estimation: Journal Version 指導老師：童曉儒 教授 報告人：張益瑞 1 2016/2/23

2. Outline Introduction Related Work MPEG-4 Background The Video Transport Protocol VTP Implementation Experimental Evaluation Conclusion 2 2016/2/23

3. Introduction Video streams are usually delivered via UDP with no transport layer congestion control. Video streams are loss tolerant and delay sensitive. TCP involves the repeated halving and growth of its congestion window, following Additive Increase/Multiplicative Decrease (AIMD) algorithm. 3 2016/2/23

4. Introduction 4 2016/2/23

5. Introduction We design and implement a protocol that attempt to maximize the quality of real-time MPEG-4 video streams while simultaneously providing basic end-to-end congestion control. Video Transport Protocol (VTP) delivers consistent quality video in moderately congested networks and fairly shares bandwidth with TCP. 5 2016/2/23

6. Introduction Primary goal of adapting video stream to the characteristics of the network path between sender and receiver.(VTP sends packets using UDP, adding congestion control at the application layer.) Secondary goal of VTP is the minimal use of network and computer resources.(bandwidth and memory) 6 2016/2/23

7. Related Work Service model for multimedia streaming fall into two categories: 1.Modifications or enhancements to AIMD congestion control to better accommodate streaming applications. 2.Model-based flow control based primarily on TCP- Friendly Rate Control (TFRC) 7 2016/2/23

8. Related Work Rate Adaptation Protocol (RAP) :rate based protocol, receiver feedback, no fairness with TCP. Stream Control Transmission Protocol (SCTP) :multi-streaming, congestion control in SCTP is identical to TCP. TCP-Friendly Rate Control (TFRC) : maintain the sending rate at the level of a TCP flow under the same conditions. 8 2016/2/23

9. Related Work TCP’s behaviors of poor link utilization in high-loss environments and unfairness. VTP aims to be adaptive and flexible by making minimal assumptions about the network and using network feedback as a indicator, not as rigorous set of input parameters. 9 2016/2/23

10. MPEG-4 Background High bitrate scalability and compression efficiency Spatial and temporal redundancy in individual frames Object-based encoding ▫ Video objects (VOs) ▫ Video object planes (VOPs) ▫ Group of Video Object Planes (GOV) 10 2016/2/23

11. MPEG-4 Background (I-VOPs) (P-VOPs) (B-VOPs) 11 2016/2/23

12. MPEG-4 Background 12 2016/2/23

13. MPEG-4 Background Macroblock Slice Quantization Parameters(QPs): 量化參數較高就 是較高的壓縮率 與 low quality 。 13 2016/2/23

14. MPEG-4 Background/ VTP policy 14 2016/2/23

15. The Video Transport Protocol Sender and Receiver Interaction Bandwidth Estimation and Rate Adjustment Rate Based Congestion Control 15 2016/2/23

16. The Video Transport Protocol(concept) Communication between sender and receiver is a “closed loop,” the receiver sends acknowledgments to the sender at regular intervals. The bandwidth of the forward path is estimated and used by the sender to determine the sending rate. VTP is rate based. There is no congestion window or slow start phase. 16 2016/2/23

17. Sender and Receiver Interaction 17 2016/2/23 RTT measurement & bandwidth computation

18. Bandwidth Estimation and Rate Adjustment 18 2016/2/23 b: rate sample d: data bytes t: time B: bandwidth estimate α : weighting factor

19. Bandwidth Estimation and Rate Adjustment (Finite State Machine, FSM) 19 2016/2/23 Q: video encoding levels IR: increase rate states DR: decrease rate states

20. Rate Based Congestion Control VTP is to adapt the outgoing video stream so that, in times of network congestion, less video data is sent into the network and consequently fewer packets are lost and fewer frames are discarded. VTP performs a type of congestion avoidance: it increases its rate by a small amount on every estimated RTT. 20 2016/2/23

21. VTP Implementation Software Architecture Transmission Schedules for Variable Bitrate Video Minimizing Client Buffer Requirements 21 2016/2/23

22. Software Architecture 22 2016/2/23

23. Software Architecture 23 2016/2/23

24. Transmission Schedules for Variable Bitrate Video 24 2016/2/23 V(t): the cumulative amount of bytes consumed by the client from the start of the streaming session to time t C(t): CBR schedule ν(τ): the video is encoded at a variable rate U(t): Utilization

25. Transmission Schedules for Variable Bitrate Video 25 2016/2/23

26. Minimizing Client Buffer Requirements 26 2016/2/23 Buffer 沒 有使用過 多或不足 的情形

27. Minimizing Client Buffer Requirements 27 2016/2/23 Quantization parameters(QPs): 量化參數高就是較高的壓縮率與 low quality 。 (DivX)

28. Minimizing Client Buffer Requirements 28 2016/2/23 Quantization parameters(QPs): 量化參數高就是較高的壓縮率與 low quality 。 (FFMpeg) FFmpeg are smaller and use less bandwidth than DivX for the same QPs

29. Experimental Evaluation Basic Protocol Behavior Fairness with TCP Random Link Errors Comparison with TFRC Video Quality 29 2016/2/23

30. Basic Protocol Behavior 30 2016/2/23 One of the main goals of VTP is to fairly share network resources with other traffic. VTP attempts to achieve fairness with TCP by reducing its sending rate whenever the bandwidth estimate indicates that the current rate cannot be supported.

31. Basic Protocol Behavior 31 2016/2/23 理想的 sending rate ：依估計的 bandwidth 調整 sending rate 。

32. Fairness with TCP 32 2016/2/23

33. Fairness with TCP 33 2016/2/23

34. Random Link Errors 34 2016/2/23 從 random error 的角度來看， VTP 不因 TCP 發生大量 error 而快速搶占 TCP 的頻寬，只是平緩的增加 traffic 。

35. Comparison with TFRC 35 2016/2/23 s: packet size R: RTT p: the steady state loss event rate t RTO : the value of the TCP retransmit timeout T: transmit rate

36. Comparison with TFRC 36 2016/2/23

37. Video Quality 37 2016/2/23 Quantization parameters(QPs): 量化參數高就是較高的壓縮率與 low quality 。

38. Video Quality 38 2016/2/23 從 Frame rate 的角度來看，使用 VTP 可達到較穩定的 Frame rate 。

39. Video Quality 39 2016/2/23 從 Frame rate 的角度來看，使用 VTP 可達到較穩定的 Frame rate 。

40. Video Quality 40 2016/2/23 QPs 減低 3 ~ 5 可維持略高的影片品質。

41. Conclusion VTP is the use of bandwidth estimation to adapt the sending rate and the video encoding in response to changes in network conditions We found that VTP fairness toward TCP is vulnerable if the lowest video bitrate is higher than the average link fair share available to VTP. 41 2016/2/23