How to Meet the Deadline
   for Packet Video

            Bernd Girod
            Mark Kalman
             Eric Setton
   ...
THE MEANING OF FREE SPEECH

                              The acquisition by eBay of Skype is a
                          ...
IPTV is Becoming a Reality
                                                  Verizon
                                     ...
Why Is Internet Video Hard?

   Internet is a best-effort network . . .

   Congestion                 Insufficient rate t...
How to Meet the Deadline for Packet Video




B. Girod: Packet Video 2006                     5
How to Meet the Deadline for Packet Video




                              Internet




B. Girod: Packet Video 2006      ...
How to Meet the Deadline for Packet Video

 • Congestion, QoS, and “fair” sharing
 • Maximum-utility resource allocation f...
Measuring Congestion
                                E[Delay]
                              “Congestion”




             ...
Congestion Grows
       Nonlinearly with Link Utilization
                              Congestion D
                     ...
How 1B Users Share the Internet
                                               Rate R
      TCP Throughput
               ...
QoS vs. Best Effort
    Reservation-ism                       Best Effort-ism
         – Voice and video need             ...
Simple Model of A Shared Link
    • Link of capacity C is shared among k flows

                                     C
   ...
Rigid Applications
                                         u
    • Utility u=0 below of
                                 ...
Elastic Applications
                                   u(R)
    • Elastic applications:
      convex utility
      functi...
QoS vs. Best Effort for Video
     • H.264 video coding for 2                                           • Video is elastic...
Different Utility Functions
         uk                                     Equal-slope
                                  ...
Distribution of TV over WLAN
                                       5 Mbps




                                           ...
Video over WLAN

                                      Network
                                      Interface            ...
Video over WLAN with Multiple Streams


                       Transcoder
                           0                    ...
Dynamic Estimation of R-D Curve
                                               Scene cuts     R-D Model
                  ...
802.11b Transmission of 2 Video Streams
        channel capacity
                           4000
          Link
         r...
Video Distortion with Self Congestion

              Good
              Picture
              quality
                    ...
Effect of Playout Delay and Loss Sensitivity


                  Foreman                                      Salesman


 ...
Simulation of 600 kbps link
                           Latency 400 msec




                                      1 sender...
Modeling Self-Congestion
                         for Packet Scheduling
               • Rate-distortion optimized packet ...
CoDiO Light Scheduler
                                  P
      I      B     B      B   P   B I      B
                   ...
CoDiO Scheduling Performance
           Mother & Daughter                                           News



            30...
CoDiO                                                  ARQ




                                          H.264/AVC @250 kb...
CoDiO vs. RaDiO


                           60 %


                                           Playout deadline (s)




  ...
Video Multicast over P2P Networks
Challenges
• Limited bandwidth                          … stream
                       ...
Experimental Setup
    • Network/protocol simulation in ns-2     Downlink    Uplink    Percentage
         – 300 active pe...
Join and Rejoin Latencies




                               Simulations over ns-2, 300 peers
                            ...
P2P Video Multicast: 64 out of 300 Peers




         CoDiO retransmissions                          No retransmissions

 ...
P2P Video Multicast: 64 out of 300 Peers




         CoDiO retransmissions                          No retransmissions

 ...
CoDiO Scheduling for Multicast Trees


                                             Child



     Parent

      I      B  ...
Gain by Multicast CoDiO
                    Foreman                                               Mother & Daughter



   ...
Average Video Sequence for 75 Peers




       Sender-driven CoDiO light                           Without prioritization
...
Conclusions
    • Must avoid congestion for low latency
    • Video streaming over bottlenecks (IPTV, WLAN . . . ):
      ...
The End
http://www.stanford.edu/~bgirod/publications.html
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Mobile, Multimedia and Beyond

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Mobile, Multimedia and Beyond

  1. 1. How to Meet the Deadline for Packet Video Bernd Girod Mark Kalman Eric Setton Information Systems Laboratory Stanford University
  2. 2. THE MEANING OF FREE SPEECH The acquisition by eBay of Skype is a helpful reminder to the world's trillion- dollar telecoms industry that all phone calls will eventually be free . . . . . . Ultimately—perhaps by 2010—voice may become a free internet application, with operators making money from related internet applications like IPTV . . . [Economist, September 2005] B. Girod: Packet Video 2006 2
  3. 3. IPTV is Becoming a Reality Verizon 10M IPTV households by 2009 SBC (ATT) 18M IPTV households by 2007 [IEEE Spectrum, Jan. 2005] B. Girod: Packet Video 2006 3
  4. 4. Why Is Internet Video Hard? Internet is a best-effort network . . . Congestion Insufficient rate to carry all traffic Packet loss Impairs perceptual quality Delay Impairs interactivity of services; Zapping < 500 ms B. Girod: Packet Video 2006 4
  5. 5. How to Meet the Deadline for Packet Video B. Girod: Packet Video 2006 5
  6. 6. How to Meet the Deadline for Packet Video Internet B. Girod: Packet Video 2006 6
  7. 7. How to Meet the Deadline for Packet Video • Congestion, QoS, and “fair” sharing • Maximum-utility resource allocation for multiple video streams • Example: video over wireless home networks • Congestion-distortion optimized packet scheduling (CoDiO) • Example: P2P multicasting of live video • Packet scheduling for multicast trees B. Girod: Packet Video 2006 7
  8. 8. Measuring Congestion E[Delay] “Congestion” Traffic flow Congestion in packet-switched network: queuing delay that packets experience, •weighted by size of the packet •averaged over all packets in the network B. Girod: Packet Video 2006 8
  9. 9. Congestion Grows Nonlinearly with Link Utilization Congestion D [seconds] Example: M/M/1 model 1 D= C-R C Rate R B. Girod: Packet Video 2006 9
  10. 10. How 1B Users Share the Internet Rate R TCP Throughput maximum transfer data rate unit Growing congestion 1.22  MTU R RTT  p packet loss rate p round 0.0001 0.001 0.01 0.1 trip time [Mahdavi, Floyd, 1997] [Floyd, Handley, Padhye, Widmer, 2000] B. Girod: Packet Video 2006 10
  11. 11. QoS vs. Best Effort Reservation-ism Best Effort-ism – Voice and video need – Best Effort good enough for guaranteed QoS all applications (bandwidth, loss, delay) – Real-time applications can – Requires admission control: be made adaptive to cope “Busy tone” when network with any level of service is full – Overprovisioning always – Best effort is fine for data solves the problem, and it’s applications cheaper than QoS guarantees B. Girod: Packet Video 2006 11
  12. 12. Simple Model of A Shared Link • Link of capacity C is shared among k flows C • Fair sharing: each admitted flow uses rate R=C/k • Homogeneous flows with same utility function u(R) • Total utility C U k   k u  R  k u   k [Breslau, Shenker, 1998] B. Girod: Packet Video 2006 12
  13. 13. Rigid Applications u • Utility u=0 below of 1 minimum bit-rate B B C/k C  • Admit at most k    flows B • With sufficient overprovisioning, no admission control needed, since  C  Pr k      0   B  B. Girod: Packet Video 2006 13
  14. 14. Elastic Applications u(R) • Elastic applications: convex utility function u(R) • All flows should be admitted: best effort! R B. Girod: Packet Video 2006 14
  15. 15. QoS vs. Best Effort for Video • H.264 video coding for 2 • Video is elastic application different testsequences . . . above a certain Good picture 44 minimum quality quality 42 • Bottleneck links: admission 40 control and dynamic rate 38 control combined Y-PSNR in dB 36 34 • Rate must be adapted to 32 network throughput. How? 30 Foreman mobile • Utility function depends on Bad 28 foreman Mobile content: should use unequal picture 26 rate allocation quality 24 0 500 1000 1500 2000 2500 3000 3500 4000 encoding rate in kbps B. Girod: Packet Video 2006 15
  16. 16. Different Utility Functions uk Equal-slope “Pareto condition” Vilfredo Pareto rk 1848-1923 • Better than utility-oblivious “fair” sharing • With rk>=0  Karush-Kuhn-Tucker conditions B. Girod: Packet Video 2006 16
  17. 17. Distribution of TV over WLAN 5 Mbps 11 Mbps 2 Mbps Home Media Gateway [courtesy: van Beek, 2004] B. Girod: Packet Video 2006 17
  18. 18. Video over WLAN Network Interface playout 802.11b buffer Receiver Transcoder Decoder Video encoded at higher rate Wireless Terminal Controller [Kalman, van Beek, Girod 2005] B. Girod: Packet Video 2006 18
  19. 19. Video over WLAN with Multiple Streams Transcoder 0 Decoder Network c0 0 Transcoder Interface Receiver … 1 Decoder c1 … 1 … (Multi-Channel) … Transcoder M cM Decoder M Controller Wireless terminals [Kalman, van Beek, Girod 2005] B. Girod: Packet Video 2006 19
  20. 20. Dynamic Estimation of R-D Curve Scene cuts R-D Model 45  D  D0  R  R0 40 35 [Stuhlmüller et al. 2000] Y-PSNR in dB 30 25 Parameters track weighted average of 20 last I-Frame, P-Frame and B-Frame 15 10 5 1 2 3 4 5 time in seconds B. Girod: Packet Video 2006 20
  21. 21. 802.11b Transmission of 2 Video Streams channel capacity 4000 Link rates in kbs 2000 [kbps] 0 0 5 10 15 20 25 30 1 channel-time allocation Channel time 0.5 allocation 0 0 5 10 15 20 25 30 2000 rate in kbps transcoded Transcoder bit-rate 1000 [kbps] 0 0 5 10 15 20 25 30 15 backlog in frames 10 Backlog in frames 5 0 0 5 10 15 20 25 30 50 Mean PSNR: 31 dB Y-PSNR 40 PSNR in dB in dB 30 20 10 0 5 10 15 20 25 30 time in seconds B. Girod: Packet Video 2006 21
  22. 22. Video Distortion with Self Congestion Good Picture quality Self congestion causes late loss Bad picture quality Bit-Rate [kbps] B. Girod: Packet Video 2006 22
  23. 23. Effect of Playout Delay and Loss Sensitivity Foreman Salesman 40% headroom 10% Simulations over ns-2 Link capacity 400 kb/s B. Girod: Packet Video 2006 23
  24. 24. Simulation of 600 kbps link Latency 400 msec 1 sender 380 kbps, 36 dB 420 kbps, 33.7 dB Highest sustainable video quality B. Girod: Packet Video 2006 24
  25. 25. Modeling Self-Congestion for Packet Scheduling • Rate-distortion optimized packet scheduling (RaDiO) typically assumes independent delay pdfs for successive packet transmissions [Chou, Miao, 2001] • Model delay pdf by exponential with varying shift distribution Probability delay [Setton, Girod, 2004] B. Girod: Packet Video 2006 25
  26. 26. CoDiO Light Scheduler P I B B B P B I B B BB B P I I P B B B B Pictures to send Schedule B. Girod: Packet Video 2006 26
  27. 27. CoDiO Scheduling Performance Mother & Daughter News 30 % 25 % Playout deadline (s) Playout deadline (s) Simulations over ns-2 Packet loss rate 2% Bandwidth 400 kb/s Propagation delay: 50ms B. Girod: Packet Video 2006 27
  28. 28. CoDiO ARQ H.264/AVC @250 kb/s Link rate 400 kb/s, propagation delay 50 ms 2 % packet loss 0.6 second playout deadline B. Girod: Packet Video 2006 28
  29. 29. CoDiO vs. RaDiO 60 % Playout deadline (s) Playout deadline (s) Sequence: Foreman Packet loss rate 2% Link capacity 400 kb/s Propagation delay: 50ms Playout deadline (s) B. Girod: Packet Video 2006 29
  30. 30. Video Multicast over P2P Networks Challenges • Limited bandwidth … stream Video … • Delay due to multi-hop transmission • Unreliability of peers Our Approach [Setton, Noh, Girod, 2005] • Determine encoding rate as a function of network bandwidth • Build and maintain complementary multicast trees • Adapt media scheduling to network conditions and to content • Request retransmissions to mitigate losses Related work • [Chu, Rao, Zhang, 2000] • [Padmanabhan, Wang and Chou, 2003] • [Guo, Suh, Kurose, Towsley, 2003] • [Cui, Li, Nahrstedt, 2004] • [Do, Hua, Tantaoui, 2004] • [Hefeeda, Bhargava, Yau, 2004] • [Zhang, Liu, Li and Yum, 2005] • [Zhou, Liu, 2005] • [Chi, Zhang, Packet Video 2006] B. Girod: Packet Video 2006 30
  31. 31. Experimental Setup • Network/protocol simulation in ns-2 Downlink Uplink Percentage – 300 active peers 512 kb/s 256 kb/s 56% 3 Mb/s 384 kb/s 21% – Random peer arrival/departure 1.5 Mb/s 896 kb/s 9% average life-time 5 minutes 20 Mb/s 2 Mb/s 3% – Over-provisioned backbone 20 Mb/s 5 Mb/s 11% – Typical access rate distribution [Sripanidkulchai et al., 2004] – Delay: 5 ms/link + congestion • Video streaming – H.264/AVC encoder @ 250 kb/s – 15 minute live multicast [Setton, Noh, Girod, 2005] B. Girod: Packet Video 2006 31
  32. 32. Join and Rejoin Latencies Simulations over ns-2, 300 peers Number of trees: 4 Retransmissions enabled [Setton, Noh, Girod, 2005] B. Girod: Packet Video 2006 32
  33. 33. P2P Video Multicast: 64 out of 300 Peers CoDiO retransmissions No retransmissions H.264 @ 250 kb/s 2 second playout deadline for all streams B. Girod: Packet Video 2006 33
  34. 34. P2P Video Multicast: 64 out of 300 Peers CoDiO retransmissions No retransmissions H.264 @ 250 kb/s 2 second playout deadline for all streams B. Girod: Packet Video 2006 34
  35. 35. CoDiO Scheduling for Multicast Trees Child Parent I B P B P B P DI DB DP3 DB DP2 DB DP1 Child Treesize  E D  D  min. [Setton, Noh, Girod, 2006] B. Girod: Packet Video 2006 35
  36. 36. Gain by Multicast CoDiO Foreman Mother & Daughter 30 % 40 % Playout deadline (s) Playout deadline (s) Simulations over ns-2, 300 peers Number of trees: 4 [Setton, Noh, Girod, 2006] Retransmissions enabled B. Girod: Packet Video 2006 36
  37. 37. Average Video Sequence for 75 Peers Sender-driven CoDiO light Without prioritization 33.71 dB 30.17 dB H.264 @ 250 kb/s 0.8 second playout deadline for all streams B. Girod: Packet Video 2006 37
  38. 38. Conclusions • Must avoid congestion for low latency • Video streaming over bottlenecks (IPTV, WLAN . . . ): combine admission control and rate control • R-D-aware rate allocation better than fair sharing • Packet scheduling should consider congestion rather than rate • Low-complexity CoDiO scheduler • P2P video multicast possible with low latency • Retransmissions effective with application-layer multicast • CoDiO extended to packet scheduling for multicast trees Cross-layer paradigm Media-aware transport  superior system performance B. Girod: Packet Video 2006 38
  39. 39. The End http://www.stanford.edu/~bgirod/publications.html

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