It is not Beauty I Demand – George Darley

1. It is not Beauty I Demand – George Darley

2. Video on Demand • One video server • Many video data • Many clients • Client want to watch at any time NUS.SOC.CS5248 OOI WEI TSANG

3. Assumptions • Constant bitrate stream • Perfect network transport NUS.SOC.CS5248 OOI WEI TSANG

4. Unicast Solution • One channel per client • No start-up latency • No client buffer • Low client bandwidth • Large server bandwidth • Not scalable NUS.SOC.CS5248 OOI WEI TSANG

5. Multicast Solution • Batching • aggregate client requests • serve using multicast • clients have to wait • No client buffer • Low client bandwidth “Scheduling Policies for an On-Demand Video Server with Batching” Dan, Sitaram, Shahabuddin, IBM NUS.SOC.CS5248 OOI WEI TSANG

6. Multicast Solution • User-centered approach • Scheduling data based on user requests • Data-centered approach • Don’t care about user • Just broadcast popular video NUS.SOC.CS5248 OOI WEI TSANG

7. Multicast Solution • Batching • Staggered Broadcast NUS.SOC.CS5248 OOI WEI TSANG

8. Staggered Broadcast Video C0 C1 C2 : NUS.SOC.CS5248 OOI WEI TSANG

9. Staggered Broadcast • 2 hour video • 5 minutes waiting time • Number of channels = 2 x 60 / 5 = 24 • Required bandwidth = 1.5Mbps x 24 = 36Mbps NUS.SOC.CS5248 OOI WEI TSANG

10. Multicast Solution • Batching • Staggered Broadcast • clients have to wait • No client buffer • Low client bandwidth • Huge server bandwidth NUS.SOC.CS5248 OOI WEI TSANG

11. Multicast Solution • Batching • Staggered Broadcast • Periodic Broadcast NUS.SOC.CS5248 OOI WEI TSANG

12. Periodic Broadcast Video C0 C1 C2 : NUS.SOC.CS5248 OOI WEI TSANG

13. Pyramid Broadcast Video C0 C1 C2 : NUS.SOC.CS5248 OOI WEI TSANG

14. Pyramid Broadcast Video 1 Video 2 C0 C1 C2 : NUS.SOC.CS5248 OOI WEI TSANG

15. Pyramid Broadcast Video C0 C1 C2 : NUS.SOC.CS5248 OOI WEI TSANG

16. Analysis of Pyramid Broadcast • Notations • B : Total available bandwidth • Bv : Bandwidth of video • Tv : Total length of each video • K : Number of segments per video • Ti : Length of segment i •  : Factor in geometric series NUS.SOC.CS5248 OOI WEI TSANG

17. Channel Bandwidth playback time = Ti i i+1 i+1 D’oh! Just miss it! download time = Ti+1Bv/Bi Download time for Ti+1 needs to be smaller than Ti for segment i+1 to arrive in time. NUS.SOC.CS5248 OOI WEI TSANG

18. Channel Bandwidth NUS.SOC.CS5248 OOI WEI TSANG

19.  = 2 NUS.SOC.CS5248 OOI WEI TSANG

20. Start-up Latency • Worst case waiting time = T1 NUS.SOC.CS5248 OOI WEI TSANG

21. Optimal  T1  2.5 NUS.SOC.CS5248 OOI WEI TSANG

22. Storage Requirements ~ (TK + TK-1)Bv NUS.SOC.CS5248 OOI WEI TSANG

23. Pyramid Broadcast • Large client bandwidth (KBv) • Huge client buffer (70–80% Tv) NUS.SOC.CS5248 OOI WEI TSANG

24. Permutation-based Pyramid Broadcast C0 C1 C2 NUS.SOC.CS5248 OOI WEI TSANG

25. Channel Bandwidth playback time = Ti i i+1 i+1 i+1 i+1 D’oh! Just miss it! download time = Ti+1Bv/Bi X X needs to be smaller than Ti for segment i+1 to arrive in time. NUS.SOC.CS5248 OOI WEI TSANG

26. Channel Bandwidth p : number of sub-channels per segments NUS.SOC.CS5248 OOI WEI TSANG

27. Client Latency Just T1/p NUS.SOC.CS5248 OOI WEI TSANG

28. Storage Requirement • One channel at a time • Can pause and wait NUS.SOC.CS5248 OOI WEI TSANG

29. Storage Requirement pause k-1 k-1 k resume k Within time X, better not consume all data in buffer. X NUS.SOC.CS5248 OOI WEI TSANG

30. Storage Requirement Let buffer content be of size M Time to consume the buffer = M/Bv NUS.SOC.CS5248 OOI WEI TSANG

31. Comparisons Carter, Long and Paris “Video on Demand Broadcasting Protocols” NUS.SOC.CS5248 OOI WEI TSANG

32. Pyramid Broadcasting NUS.SOC.CS5248 OOI WEI TSANG

33. Skyscraper Broadcasting • Observations: • storage requirement is affected by size of the largest chunk So, let’s limit the size of the largest chunk! NUS.SOC.CS5248 OOI WEI TSANG

34. Pyramid Skyscraper NUS.SOC.CS5248 OOI WEI TSANG

35. Skyscraper Broadcasting • Uses series 1 2 2 5 5 12 12 25 25 52 52 … W W W NUS.SOC.CS5248 OOI WEI TSANG

36. Skyscraper Example NUS.SOC.CS5248 OOI WEI TSANG

37. Skyscraper Example NUS.SOC.CS5248 OOI WEI TSANG

38. Comparisons Carter, Long and Paris “Video on Demand Broadcasting Protocols” NUS.SOC.CS5248 OOI WEI TSANG

39. Other schemes • Pagoda Broadcasting1 3 5 15 25 75 125 … • Harmonic Broadcasting Equal segment size, varies bandwidth instead! NUS.SOC.CS5248 OOI WEI TSANG

40. Multicast Solution • Batching • Staggered Broadcast • Periodic Broadcast • Sending rate ≥ playback rate • May need multiple channels • Need additional client buffer • Need to wait NUS.SOC.CS5248 OOI WEI TSANG

41. Multicast Solution • Batching • Staggered Broadcast • Periodic Broadcast • Patching NUS.SOC.CS5248 OOI WEI TSANG

42. Patching Time mcast unicast Client Request NUS.SOC.CS5248 OOI WEI TSANG

43. Patching Patching Window: W Time mcast mcast Client Request NUS.SOC.CS5248 OOI WEI TSANG

44. Grace Patching ifW < B client buffer video[W .. end] unicast video[0 .. W] else mcast video[0 .. end] NUS.SOC.CS5248 OOI WEI TSANG

45. Example • 30 minutes video • 15 minutes buffer • One request per minute NUS.SOC.CS5248 OOI WEI TSANG 465.271.225

46. Example • What if patching window = 5 min? NUS.SOC.CS5248 OOI WEI TSANG

47. Supporting VCR Operations • Pause • Fast Forward • Rewind • Forward Search • Backward Search • Slow Mo NUS.SOC.CS5248 OOI WEI TSANG

48. Two Types of Operations • Continuous (all) • Discrete Time (pause,ff,rwd) NUS.SOC.CS5248 OOI WEI TSANG

49. Discrete Time • Easier to implement • Simple in staggered broadcasting NUS.SOC.CS5248 OOI WEI TSANG

50. Continuous Time • Requires buffering of future frames and previous frames Abram-Profeta and K.G. Shin, "Providing Unrestricted VCR Functions in Multicast Video-on-Demand Servers," NUS.SOC.CS5248 OOI WEI TSANG