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Adjusting Forward Error Correction for TCP- Friendly Streaming MPEG

Adjusting Forward Error Correction for TCP- Friendly Streaming MPEG. Huahui Wu, Mark Claypool & Robert Kinicki Computer Science Department Worcester Polytechnic Institute Worcester, MA, 01609 USA {flashine,claypool,rek}@cs.wpi.edu. TCP-Friendly Flows.

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Adjusting Forward Error Correction for TCP- Friendly Streaming MPEG

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  1. Adjusting Forward Error Correction for TCP- Friendly Streaming MPEG Huahui Wu, Mark Claypool & Robert Kinicki Computer Science Department Worcester Polytechnic Institute Worcester, MA, 01609 USA {flashine,claypool,rek}@cs.wpi.edu

  2. TCP-Friendly Flows • Unresponsive flows get unfair share of network bandwidth and AQM techniques will punish them. • Streaming flows need to be TCP-Friendly. • A TCP-Friendly flow’s bandwidth is no more than a conformant TCP flow running under comparable network conditions. [PFTK98]

  3. Forward Error Correction (FEC) • Packet loss degrades video quality. • FEC adds redundancy to recover from losses. • With an MPEG frame made up of K ordinary packets, FEC adds N-K redundant packets to frame. • If K or more of the N packets are received, the original frame can be successfully reconstructed. • The successful frame transmission probability is

  4. MPEG with FEC • Prior Approaches • were ad-hoc and did not consider TCP-Friendliness. • Our Approach: Adjusting FEC and GOP • Forces TCP-Friendly bandwidth constraint. • Develops an analytic model to compute playable frame rate for given FEC and GOP pattern. • Exhaustively searches for FEC and GOP pattern that optimizes playable frame rate.

  5. Playable Frame Rate Model (1 of 2) • GOP rate (Group of Pictures per second): • Playable Frame Rate of I, P and B frames

  6. Playable Frame Rate Model (2 of 2) • Given values of loss rate and frame size, the total playable frame rate can be estimated with the FEC and GOP pattern. • The best playable frame rate can be obtained by searching the FEC and GOP space.

  7. Benefits from Adjusting FEC and/or GOP RTT: 50ms s: 1KB p(%):0.5, 1, 2, 3, 4, … 10 SI: 25 packets SP: 8 packets SB: 3 packets

  8. Adjusted GOP and FEC pattern Adjusted GOP pattern Y-axis: Number of frames X-axis: Loss percentage Adjusted FEC pattern Y-axis: Number of packets X-axis: Loss percentage

  9. Contribution Summary • Contribution • Built a model to estimate the playable frame rate with GOP and FEC pattern for MPEG. • Used the model to study adjusting FEC and GOP • Adjusting FEC provides large benefit. • Adjusting GOP contributes little improvement. • Ongoing Work • Model verification with realistic network • Adjustable FEC combined with Media Scaling.

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