1. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 1 Error Recovery

2. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 2 Problems with Internet Limited Bandwidth Varying Conditions Delay Jitter Packet Loss Delay Heterogeneity :

3. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 3 Network Encoder Sender Middlebox Receiver Decoder You Are Here

4. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 4 Overview Characteristics of the Internet General techniques Error recovery for audio Effect of loss on MPEG Error recovery for MPEG

5. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 5 Loss Characteristics of The Internet

6. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 6 Characteristics of Internet 60-70% of paths do not show any loss Those with loss have an average of 4.5 – 6% packet loss [Paxson97] End-to-end Internet packet dynamics

7. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 7 Packet Loss Pattern 1000 30 Number of Occurrences Burst Length

8. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 8 Characteristics of Internet Bursts of loss are typically short (2-3 consecutively loss packets) Long burst do occur Burst may occur periodically

9. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 9 Wireless Link Loss rate measured in my office 10 ~ 20% up to 50% reported!

10. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 10 Gilbert Model GOODBAD

11. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 11 A Survey of Packet-Loss Recovery Techniques for Streaming Audio Perkins, Hodson and Hardman IEEE Network Magazine 1998

12. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 12 Retransmission 1234 124 3 3 X

13. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 13 Redundant Data 1234 124 2 23 345 53

14. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 14 24 Error Concealment 1234 1

15. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 15 Retransmission for audio

16. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 16 Pros/Cons of Retransmissions

17. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 17 Scalable Retransmission On packet loss T = random(0, RTT) wait for T multicast NACK On receiving NACK from others suppress own NACK

18. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 18 Retransmit when Group size is small Loss rate is low Large latency acceptable

19. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 19 Selective Retransmission Retransmission based on priority of packets Important/urgent packets are retransmitted first

20. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 20 Redundant Data for audio

21. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 21 Parity Forward Error Correction 1011001 1000010 0001001 XOR 0010010

22. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 22 Parity Forward Error Correction 1011001 1000010 0001001 0010010

23. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 23 Parity FEC Ordering

24. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 24 Parity FEC Ordering

25. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 25 Parity FEC Ordering

26. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 26 Parity FEC Ordering

27. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 27 Parity FEC Ordering

28. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 28 Reed-Solomon Code RS(n,k) RS n k (popular: n = 223) (popular: k = 32) Parity symbols Data symbols

29. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 29 Reed-Solomon Code Data block (length n+k, e.g., 255) Can correct up to 16 corrupted symbols per block (32/2)

30. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 30 Media Specific FEC 1234 124 2 23 345 53

31. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 31 Pros/Cons of Redundant Data

32. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 32 Interleaving

33. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 33 Pros/Cons of Interleaving

34. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 34 Error Concealment

35. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 35 Effect of Loss on Audio Speech Human ears can interpolate Loss up to length of phoneme can still be tolerable

36. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 36 Insertion-based Repair Splice Silence Substitution Noise Substitution Repetition

37. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 37 Other Repair Methods Interpolation Regeneration

38. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 38 Error Concealment More complex error concealment algorithms provide better performance (i.e., playback quality)

39. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 39 Colin’s Recommendations

40. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 40 Non-Interactive Apps Interleaving FEC Retransmission for unicast only

41. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 41 Interactive Applications Media Specific FEC

42. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 42 Error Concealment Repeat

43. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 43 Packet Loss Effects on MPEG Video Sent over the Public Internet Jill Boyce and Robert Gaglianello ACM Multimedia 1998

44. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 44 Measurement-based Study Need to understand the problem before proposing solution

45. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 45 Data Gathering Method From: NYC 13, Austin 21, London 18 To: Holmdel, NJ

46. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 46 Data Gathering Method Video: Two 5-mins MPEG 30 fps 384 kbps and 1 Mbps IBBPBBPBBPBBPBB QSIF 176x112 and SIF 352x240 One row per slice

47. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 47 Average Packet Loss

48. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 48 Frames Affected by Errors % Frames in Error Packet Loss Rate

49. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 49 Overview of Error Recovery for Video

50. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 50 Methods Retransmission Interleaving Error Concealment FEC Limiting Error Propagation Reference Frame Selection

51. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 51 Reference Frame Selection I P B B P X I

52. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 52 Methods Retransmission Interleaving Error Concealment FEC Limiting Error Propagation Reference Frame Selection Changing Temporal Pattern

53. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 53 Case Study: HD video conferencing Korean Air, Inha University (Seoul), University of Southern California, Pratt & Whitney

54. © PWICE, 200654 USC-Inha Two-way Experiments USC (Powell Hall of Engineering) July 2005

55. © PWICE, 200655 USC-Inha Two-way Experiments Inha University (Memorial Library) July 2005

56. © PWICE, 200656 KAL Network Infrastructure Korean Air network infrastructure between Incheon, Kimpo, and Pusan KAL network & external ISP (KT) 1 Gbps: ICN-GMP 50 Mbps: GMP-PUS December 2005

57. © PWICE, 200657 Network Measurements End-to-end packet loss rates of the network path between Kimpo (GMP) and Incheon (ICN) observed during November 15-16, 2005 Network is shared with other business traffic Loss rates are quite low November 2005

58. © PWICE, 200658 Hardware Preparation 3 computers purchased in Korea Computers sent to USC with KAL Software setup in the IMSC laboratories Linux installation RCS software installation Retransmission configuration End-to-end equipment test with local JVC cameras and displays Computers sent back to KAL HQ December 2005

59. © PWICE, 200659 Hardware Test at KAL Re-configuration for Sony HDR-HC1 cameras December 2005 Local area network tests

60. © PWICE, 200660 Experiments: ICN ◄▬► GMP Asymmetric environment: 88 Mb/s & 50 Mb/s Conclusion: ICN - GMP: sufficient BW for HD video Sufficient headroom for data applications December 2005 Bandwidth measurements Visual quality Required by RCS

61. © PWICE, 200661 Experiments: ICN ◄▬► PUS Asymmetric environment: 6 Mb/s & 1 Mb/s GMP - PUS: initially insufficient BW for HD video Investigated network routers with KAL IT help Conclusion: replaced router to improve throughput; to be re-tested December 2005 Bandwidth measurements Visual quality

62. © PWICE, 200662 Measurements: Packet Loss Rate Path: ICN - PUS Two packet sizes: 564 bytes and 940 bytes Conclusion: GMP - PUS loss rate very high December 2005 One-way packet loss rate Two-way packet loss rate

63. © PWICE, 200663 Packet Loss Error Recovery Selective retransmission protocol is used to recover from lost data Effectiveness of protocol is tested in lab environment Gilbert Model is used to induce losses into transmission Transmission delay is chosen to be 10 ms (expected latency in Korea)

64. © PWICE, 200664 Packet Loss Error Recovery Selective retransmission protocol 10% Loss Rate 5% Loss Rate 1% Loss Rate With Retransmissions Sept. - Dec. 2005 (ICN-GMP Link)

65. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 65 Error Control Techniques for Interactive Low Bitrate Video Transmission over The Internet Injong Rhee SIGCOMM ‘98

66. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 66 Basic Idea “Better Late Than Never!”, or Late packet is still useful

67. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 67 MPEG Frame Pattern IBBPBBP IPBBPBB

68. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 68 H.261 Error Propagation IPPPPPP XXXXXX IPPPPPP XXXX retransmission loss

69. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 69 H.261 Frame Pattern IPPPPPP X loss

70. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 70 IPPPPPP H.261 Frame Pattern X loss X X retransmission

71. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 71 PTDD Periodic Temporal Dependency Distance Large PTDD Higher Chance of Repair Longer Error Propagations Less Temporal Redundancy

72. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 72 QAL IPPP IPPP Base Layer Enhancement Layer

73. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 73 QAL IPPP IPPP Base Layer + FEC Enhancement Layer X

74. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 74 QAL + PTDD IPPP IPPP Base Layer Enhancement Layer

75. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 75 Error Propagation

76. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 76 Recovery from Error Propagation

77. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 77 Frame “quality” PSNR =

78. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 78 PSNR vs. Loss Rate Packet Loss Rate PSNR

79. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 79 Today’s Summary

80. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 80 How to recover packet loss Retransmission FEC Error Concealment

81. NUS.SOC.CS5248-2007 Roger Zimmermann (based on slides by Ooi Wei Tsang) 81 Limit the damage of error Interleaving Key frame selection Change reference frame