A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly Bandwidth
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Transcript of A Model for MPEG with Forward Error Correction (FEC) and TCP-Friendly Bandwidth
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
6/3/2003 NOSSDAV 2003 Monterey, California #3
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
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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.
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Outline
IntroductionRelated Knowledge
MPEG Forward Error CorrectionTCP-Friendly
Analytical ModelAnalytical ExperimentsSimulation ExperimentsSummary
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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)
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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)
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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)
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OutlineIntroductionRelated KnowledgeAnalytical Model
Successful Frame Transmission ProbabilityGOP RatePlayable Frame Rate
Analytical ExperimentsSimulation ExperimentsSummary
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Successful Frame Transmission Probability
N
Ki
iNi ppi
NpKNq )1(),,(
),,(
),,(
),,(
pSSSqq
pSSSqq
pSSSqq
BBFBB
PPFPP
IIFII
(3)
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GOP Rate
TCP Friendly Rate
)321()8
33(
32 2pp
pt
pt
sT
RTORTT
GOP Rate (GOP per second)
)()()(
/
BFBBPFPPIFI SSNSSNSS
sTG
6/3/2003 NOSSDAV 2003 Monterey, California #12
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)
6/3/2003 NOSSDAV 2003 Monterey, California #13
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)
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OutlineIntroductionRelated KnowledgeAnalytical ModelAnalytical Experiments
MethodologyImprovement on Playable Frame RateThe Behaviors of FEC
Simulation ExperimentsSummary
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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.
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Improvement of Playable Frame Rate
RTT: 50mss: 1KBp(%):0.5, 1, 2,
3, 4, … 10SI: 25 packetsSP: 8 packetsSB: 3 packets
[KSH95]
GOP: IBBPBBPBBPBBPBB
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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
6/3/2003 NOSSDAV 2003 Monterey, California #18
AFEC’s Advantage
Successful frame transmission Probability
a. Non-FEC b. Adjusting FEC
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Fixed FECs vs. Adjusted FECFixed FECs vs. Adjusted FEC
• Small: (1,1,0); Medium: (4,2,0); Large FEC: (8,4,1)
6/3/2003 NOSSDAV 2003 Monterey, California #20
Outline
IntroductionRelated KnowledgeAnalytical ModelAnalytical ExperimentsSimulation Experiments
Simulation of Dependent Packet LossSimulation of Variable Round Trip Time
Summary
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Simulation of Dependent Packet Loss
Losses are often dependentDependent loss reduce the effect of FECCause a lower playable frame rate
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Simulation of Variable Round Trip Time
a. Distribution of RTT [CCZ03] b. Effect of Variable RTT
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Outline
IntroductionRelated KnowledgeAnalytical ModelAnalytical ExperimentsSimulation ExperimentsSummary
ContributionOngoing Work
6/3/2003 NOSSDAV 2003 Monterey, California #24
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.
6/3/2003 NOSSDAV 2003 Monterey, California #25
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
6/3/2003 NOSSDAV 2003 Monterey, California #27
Benefits from Adjusting FEC and/or GOP
RTT: 50mss: 1KBp(%):0.5, 1, 2,
3, 4, … 10SI: 25 packetsSP: 8 packetsSB: 3 packets