2. Nov. 3, 2000 Adaptive Playout Scheduling in Packet Voice Communications

3. Group Meeting TalkYi Liang Outlines QoS concerns and tradeoffs The jitter adaptation scheme as a playout scheduling algorithm Setting the playout schedule Packet scaling and loss concealment Results of listening tests and performance comparison

4. Group Meeting TalkYi Liang QoS Concerns at the Receiver Delay Jitter DelayPacket Loss Obstructs proper reconstruction of voice packets at the receiver Impairs interactivity of conversations Impairs speech quality

5. Group Meeting TalkYi Liang Different Scheduling Algorithms (1)

6. Group Meeting TalkYi Liang QoS Tradeoffs (1) Playout Jitter DelayPacket Loss

7. Group Meeting TalkYi Liang Jitter Absorption vs. Jitter Adaptation Jitter Absorption Jitter Adaptation

8. Group Meeting TalkYi Liang Different Scheduling Algorithms (2) 1.Method which uses fixed playout time throughout the whole session; 2.Method which estimates delay dynamically but only adjusts playout time during silence periods; 3.Method which dynamically estimates and adjusts playout time, and scales packets within talkspurts using time-scale modification.

9. Group Meeting TalkYi Liang QoS Tradeoffs (2) Playout Jitter DelayPacket Loss

10. Group Meeting TalkYi Liang Problems How to set the playout schedule? How to scale the packet? How does playout jitter affect audio quality?

11. Group Meeting TalkYi Liang Setting the Playout Schedule

12. Group Meeting TalkYi Liang Packet Scaling

13. Group Meeting TalkYi Liang The Jitter Adaptation Procedure

14. Group Meeting TalkYi Liang Jitter Adaptation

15. Group Meeting TalkYi Liang Loss Concealment

16. Group Meeting TalkYi Liang QoS Tradeoffs (3) Playout Jitter DelayPacket Loss

17. Group Meeting TalkYi Liang Three Algorithms under Comparison 1.Method which uses fixed playout time throughout the whole session; 2.Method which estimates delay dynamically but only adjusts playout time during silence periods; 3.Method which dynamically estimates and adjusts playout time, and scales packets within talkspurts using time-scale modification.

18. Group Meeting TalkYi Liang Performance Comparison Traces measured between a host at Stanford and hosts in: 1)Chicago 2)Germany 3)MIT 4)China

19. Group Meeting TalkYi Liang Test on the Quality of Scaled Audio (1) Three short network traces with different jitter statistics Six samples are simulated over each trace; Samples are given and evaluated in pairs, in the format of “reference sample – processed sample” to provide higher sensitivity Eighteen people participated the tests Score for each condition is obtained by averaging 6x18 ratings

20. Group Meeting TalkYi Liang Test on the Quality of Scaled Audio (2) 5 Degradation is inaudible 4 Degradation is audible but not annoying 3 Degradation is slightly annoying 2 Degradation is annoying 1 Degradation is very annoying

21. Group Meeting TalkYi Liang Quality of Speech Processed by Different Algorithms (1) Four network traces with different jitter/loss statistics Four samples are simulated over each trace using two different playout scheduling algorithms (4x2 conditions) Score for each condition is obtained by averaging all the ratings

22. Group Meeting TalkYi Liang Quality of Speech Processed by Different Algorithms (2) Quality Score Excellent 5 Good 4 Fair 3 Poor 2 Bad 1 MNRU (dB)10182430Source MOS1.42.73.64.14.4

23. Group Meeting TalkYi Liang Conclusions Small jitter can be traded for lower delay and lower loss rate Infrequent packet scaling does hardly impair sound quality Using adaptive scheduling, both delay and loss rate can be significantly reduced – improved overall performance Being the results of the new tradeoffs …