A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly Bandwidth Huahui Wu, Mark Claypool & Robert Kinicki Computer Science Department Worcester

A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly Bandwidth

Huahui Wu, Mark Claypool & Robert KinickiComputer Science DepartmentWorcester Polytechnic Institute

Worcester, MA, 01609 USA{flashine,claypool,rek}@cs.wpi.edu

6/3/2003 NOSSDAV 2003 Monterey, California #2

Outline

IntroductionProtocolRepair

Related KnowledgeAnalytical ModelAnalytical ExperimentsSimulation ExperimentsSummary


Transmission Protocol

TCP uses retransmissionNo good for interactive application

UDP have no retransmissionIt doesn’t respond to congestion

TCP-Friendly [FHPW00] [RHE99]

Well behavior protocol

Loss is still an important issue


Repair and Forward Error Correction

Packet loss degrades the qualityFEC adds redundancy and fixes loss

Increase congestion to video stream

Prior Approaches Ad-hocNot TCP-Friendly

Our Approach: Adjusting FEC with TCP-Friendly bandwidth constraint.


Outline

IntroductionRelated Knowledge

MPEG Forward Error CorrectionTCP-Friendly

Analytical ModelAnalytical ExperimentsSimulation ExperimentsSummary


MPEG

Three types of framesI (Intra-coded): Coded independentlyP (Predictive-coded): obtain prediction from preceding I or P frameB (Bidirectional predictive-coded): obtain prediction from the preceding and succeeding I or P frames

Group of Picture (GOP)


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

N

Ki

iNi ppi

NpKNq )1(),,( (2)


TCP-Friendly FlowsUnresponsive 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.

)321()8

33(

32 2pp

pt

pt

sT

RTORTT

[PFTK98]

(1)


OutlineIntroductionRelated KnowledgeAnalytical Model

Successful Frame Transmission ProbabilityGOP RatePlayable Frame Rate

Analytical ExperimentsSimulation ExperimentsSummary


Successful Frame Transmission Probability

N

Ki

iNi ppi

NpKNq )1(),,(

),,(

),,(

),,(

pSSSqq

pSSSqq

pSSSqq

BBFBB

PPFPP

IIFII

(3)


GOP Rate

TCP Friendly Rate

)321()8

33(

32 2pp

pt

pt

sT

RTORTT

GOP Rate (GOP per second)

)()()(

/

BFBBPFPPIFI SSNSSNSS

sTG


Playable Frame Rate Model (1 of 2)

Playable Frame Rate of I, P and B frames

BPB

iPIP

II

qRR

qRR

qGR

iij

i

1

(4)


Playable Frame Rate Model (2 of 2)

))1

(

11(

1

1

,

P

P

P

iji

NPI

P

NPP

BBP

P

NPP

Iji

Bi

PI

qqq

qqqN

q

qqqGRRRR

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.

(5)


OutlineIntroductionRelated KnowledgeAnalytical ModelAnalytical Experiments

MethodologyImprovement on Playable Frame RateThe Behaviors of FEC

Simulation ExperimentsSummary


Methodology

Given a p, compute TCP-Friendly rate T.With a specific GOP and FEC pattern, the playable frame rate R can be computed.Search for the maximum rate Rm with all possible GOP and FEC pattern.Investigate the improvement from adjusting FEC, and the FEC behavior.


Improvement of Playable Frame Rate

RTT: 50mss: 1KBp(%):0.5, 1, 2,

3, 4, … 10SI: 25 packetsSP: 8 packetsSB: 3 packets

[KSH95]

GOP: IBBPBBPBBPBBPBB


Adjusted FEC pattern

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10

SI FSPFSBF

Y-axis: Number of packets, X-axis: Loss percentage


AFEC’s Advantage

Successful frame transmission Probability

a. Non-FEC b. Adjusting FEC


Fixed FECs vs. Adjusted FECFixed FECs vs. Adjusted FEC

• Small: (1,1,0); Medium: (4,2,0); Large FEC: (8,4,1)


Outline

IntroductionRelated KnowledgeAnalytical ModelAnalytical ExperimentsSimulation Experiments

Simulation of Dependent Packet LossSimulation of Variable Round Trip Time

Summary


Simulation of Dependent Packet Loss

Losses are often dependentDependent loss reduce the effect of FECCause a lower playable frame rate


Simulation of Variable Round Trip Time

a. Distribution of RTT [CCZ03] b. Effect of Variable RTT


Outline

IntroductionRelated KnowledgeAnalytical ModelAnalytical ExperimentsSimulation ExperimentsSummary

ContributionOngoing Work


ContributionBuilt a model to estimate the playable frame rate for TCP-Friendly MPEG Streaming.Used the model to study adjusting FEC and GOP behavior

Adjusting FEC provides large benefit. •10 to 50 times improvement in playable frame

rate with moderate to high loss probability.

Adjusting GOP provides little benefit. •More details are in the paper.


Ongoing Work

Model verification with realistic networkTCP-Friendly Video Streaming with other repair techniques.Adjusting FEC combined with Media ScalingBuild into NS-2 SimulatorImplement it in real network

A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly BandwidthHuahui Wu, Mark Claypool & Robert Kinicki

Computer Science DepartmentWorcester Polytechnic Institute

Worcester, MA, 01609 USA{flashine,claypool,rek}@cs.wpi.edu


Benefits from Adjusting FEC and/or GOP

RTT: 50mss: 1KBp(%):0.5, 1, 2,

3, 4, … 10SI: 25 packetsSP: 8 packetsSB: 3 packets

Documents

A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly Bandwidth Huahui Wu, Mark Claypool & Robert Kinicki Computer Science Department Worcester