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Rate Adaptations

This document presents adaptive algorithms for video transmission over networks, focusing on the real-time adjustments of sending rates based on network conditions. Using RTP headers, video frames are chopped into packets for UDP transmission, ensuring rates match encoding without excessive bursts. The paper discusses two primary approaches to adapt transmission rates: reducing rates under poor conditions and maintaining or increasing them under favorable conditions. TCP friendliness is considered, with goals for fair bandwidth sharing. Simulation results and technical details are drawn from relevant literature to support findings.

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Rate Adaptations

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  1. Rate Adaptations

  2. You are Here Encoder Decoder Middlebox Receiver Sender Network

  3. Sender’s Algorithm open UDP socket foreach video frame chop into packets add RTP header send to network

  4. Sender’s Algorithm open UDP socket foreach video frame chop into packets add RTP header send to network wait for 1/fps seconds

  5. Sender’s Algorithm open UDP socket foreach video frame chop into packets add RTP header send to network wait for 1/fps seconds • Send frames at equal time distance.

  6. Sender’s Algorithm open UDP socket foreach video frame chop into packets foreach packet add RTP header send to network wait for size/bps seconds • Send data at constant bandwidth.

  7. Rules • Transmission rate should match encoding rate • Transmission should not be too bursty

  8. Just send at a fix rate or “I hope the network can handle it” approach Two Approaches

  9. Effects on TCP: Simulation From Sisalem, Emanuel and Schulzrinne paper on “Direct Adjustment Algorithm.”

  10. Effects on TCP

  11. DAA Parameters • Adaptive RTP flows • Additive increase/multiplicative decrease • 50 kb and factor 0.875 • RTCP: min 5 sec inter-report time • Loss thresholds: 5% and 10% • TCP • Immediate loss notification • Transmission window is halved

  12. DAA Parameters • Adaptive RTP flows • Additive increase/multiplicative decrease • 50 kb and factor 0.875 • RTCP: min 5 sec inter-report time • Loss thresholds: 5% and 10% • TCP • Immediate loss notification • Transmission window is halfed

  13. Just send at a fixed rate or “I hope the network can handle it” approach Adapt transmission/encoding rate to network condition Two Approaches

  14. How to Adapt? if network condition is bad reduce rate else if network condition is so-so do nothing else if network condition is good increase rate

  15. How to .. • Know “network condition is bad”? • Increase/decrease rate?

  16. Adapting Output Rate if network condition is bad else if network condition is so-so do nothing else if network condition is good

  17. Adapting Output Rate Multiplicative decrease if network condition is bad else if network condition is so-so do nothing else if network condition is good Additive increase

  18. Adapting Output Rate ri Additive increase Multiplicative decrease

  19. Question: What should  and  be?

  20. Observation 1 • Should never change your rate more than an equivalent TCP stream.

  21. Observation 2 •  and  should depend on network conditions and current rate.

  22. Goal: Fair Share of Bottleneck • let r : current rateb : bottleneck bandwidth S : current share

  23. Goal: Fair Share of Bottleneck • let r : current rateb : bottleneck bandwidth S : current share

  24. S versus   S 1

  25. S versus   S 1

  26. Value of  (Assuming one receiver)

  27. Limit of  • M : packet size • : round trip time • T : period between evaluation of   Limited to the average rate increase a TCP connection would utilize during periods without losses.

  28. Loss rate versus   1 1 loss rate

  29. Loss rate versus   1 1 loss rate

  30. Value of m where is the loss rate k is a constant (Assuming one receiver)

  31. LDA Algorithm

  32. What is Needed?

  33. What is Needed? We know vi,r, M, T,  But not b

  34. Estimating b : Packet Pair

  35. Estimating b : Packet Pair

  36. Estimating b : Packet Pair

  37. Evaluation

  38. More TCP-Friendly Rate Control

  39. TCP-Equation Window size behavior in TCP/IP with constant loss probability T. Ott, J. Kemperman, and M. Mathis June 1997, HPCS 1997

  40. TCP-Equation Equation-Based Congestion Control for Unicast Applications Sally Floyd, Mark Handley, Jitendra Padhye, and Joerg Widmer.August 2000. SIGCOMM 2000

  41. Rules • Transmission rate should match encoding rate • Transmission should not be too bursty

  42. Rate Control Given a rate, how to encode the video with the given rate?

  43. Reduce Frame Rate • Live Video • Stored Video

  44. Reduce Frame Rate • Live Video • Easy (uncompressed input) • Stored Video • Difficult (frame dependencies)

  45. Reduce Frame Resolution • Live Video • Stored Video

  46. Reduce Frame Resolution • Live Video • Easy • Stored Video • Difficult

  47. Increase Quantization • Live Video • Stored Video

  48. Increase Quantization • Live Video • Easy • Stored Video • Difficult

  49. Drop AC components • Live Video • Stored Video

  50. Drop AC components • Live Video • Easy • Stored Video • Easy

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