Using Interleaving to Ameliorate the Effects of Packet Loss in a Video Stream

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Using Interleaving to Ameliorate the Effects of
Packet Loss in a Video Stream

• Mark Claypool and Yali Zhu
• Computer Science Department
• Worcester Polytechnic Institute
• Worcester, MA, USA
• http//www.cs.wpi.edu/claypool/

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Multimedia over the Internet

• Often cannot use TCP
• Interactive retransmissions add delay
• Multicast retransmissions reduce scalability
• Use UDP
• Packet loss deteriorates quality
• Forward Error Correction (FEC) not effective
  under bursty loss
• Single loss propagates with video

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Video Encoding - MPEG

• Frame types
• I-frame (Intra-coded frame)
• P-frame (Predictive-coded frame)
• B-frame (Bi-directionally predictive frames)
• GOP is I-frame to next I-Frame
• How does loss of I- or P-frame effect GOP?

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Loss Propagation in MPEG

• Loss of single frame can result in multiple
  perceived losses
• Loss of P-frame
• Loss of I-frame
• B-frame loss has no propagation

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Outline

• Introduction ?
• Interleaving ?
• Evaluation
• Conclusions

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Video Interleaving
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Benefits of Video Interleaving
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Bandwidth Costs of Interleaving

• Inter-frame encoding based on similarity among
  frames
• Interleaving decreases similarities among
  consecutive frames
• Results in bigger B- and P- frames

• Our studies ? about 15 bandwidth overhead

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Delay Costs of Interleaving

• Must delay for size of GOP frames
• Example
• Typical GOP 9 frames
• At full-motion, about 3 GOPs / second
• 1 GOP every 300 ms
• Interleaving would add 300 ms of delay

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Outline

• Introduction ?
• Interleaving ?
• Evaluation ?
• Conclusions

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User Study on Perceptual Quality

• Simulate loss results
• Loss Rates no loss, 2, 5, 10, 20
• Encode videos
• 24 video clips total
• Variety of television programming
• Ex sports, sit-com, news
• Variety of scene motion
• Watch videos
• About 40 users
• Varied order of lossy clips evaluation
• Evaluate
• Perceived quality on unlabeled scale, 1-100

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Perceptual Quality versus Loss Rate
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Comparison with Other Repair Methods
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Conclusions on Video Interleaving

• Re-ordering of original frames can reduce
  perceived effects of loss
• Loss propagation inherent in video compression
• Bursty loss
• Significantly improves perceptual quality
• Better under bursty loss than FEC
• Costs are bandwidth and delay
• Bandwidth comparable to other approaches
• Delay larger, but may be tolerable

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Future Work

• Combine repair techniques
• FEC Interleaving Retransmissions
• Adaptive system that chooses best repair
• Depends upon task
• Depends upon network conditions
• Combine with audio
• Video-Audio Interleaving