path diversity
TRANSCRIPT
Path Diversity for Media StreamingPath Diversity for Media Streaming
The Use of Multiple Description CodingThe Use of Multiple Description Coding
J. Apostolopoulos, M. Trott and W. TanJ. Apostolopoulos, M. Trott and W. Tan
Presented by Xiaoyuan GUOPresented by Xiaoyuan GUO
Outline IntroductionIntroduction Path Diversity Multiple Description Coding Systems Design, Analysis and
Operation Applications and Architectures Summary
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Background and Motivation Media Streaming Characteristics
Delay sensitive Loss tolerant
Best-effort packet networks(i.g. Internet) Delay, loss rate and available bandwidth
dynamic and unpredictable The default path is often not the best path many applications(e.g. multicast or
broadcast) lack a back channel or other means for retransmission
Media streaming is quite challenging
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Solution Path diversity + Multiple Description
Coding
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Outline Introduction Path DiversityPath Diversity Multiple Description Coding Systems Design, Analysis and
Operation Applications and Architectures Summary
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Definition and Categories Diversity: frequency, time and spatial A transmission technique that sends
data through two or more paths in a packet-based network
Categories Transmission methods
Use multiple paths at the same time Select best path
Source numbers
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Single Source Path diversity using single source
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Multiple sources Path diversity using multiple sources
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Benefits Benefits of path diversity
Bandwidth aggregation(use all at once) Traffic load balancing Reduce probability of service outage, i.g.
streaming from multiple servers in CDN or from multiple peers in P2P
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Reduce delay and jitter Reduce delay and delay jitter
Queue diversity Network delay due to backlogged queue Benefits of multiple parallel queue
Helpful Time-invariant paths having different but unknown
delay characteristics Applications of end-to-end delay constraint while
maintaining quality
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Reduce loss Reduce losses
Path selection When a single path system is unreliable and with
feedback
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Reduce Uncertainty Reduce uncertainty with averaging loss rate
Time-invariant paths lack feedback Time-varying paths that measurement lags
variation Broadcast or multicast scenarios
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Reduce Loss Decrease the probability of outage
Outage: all communication along a network path is lost for a sizable length of time
Single path p while two paths p^2 Reduce the length of burst losses
Increase the interpacket space on each path
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Outline Introduction Path Diversity Multiple Description CodingMultiple Description Coding Systems Design, Analysis and
Operation Applications and Architectures Summary
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What is it? Descriptions: sets of compressed data The more descriptions available, the
better the quality of the reproduction
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Why Use MD? SD vs. SC vs. MD
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SDSD(single (single description)description)
SCSC(Scalable (Scalable coding)coding)
MDMD(multiple (multiple des.)des.)
No scalableNo scalable
No priorityNo priority
High code High code efficiencyefficiency
ScalableScalable
Priority to base Priority to base layerlayer
Acceptable code Acceptable code efficiencyefficiency
Scalable Scalable
No priorityNo priority
Acceptable Acceptable code efficiencycode efficiency
Why Use MD?(2) Best-effect network
Packets equally to be lost or delayed Path diversity system
Send descriptions over different paths Enhance the benefits of multiple paths
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How Good MD Can Do? Rate-distortion theory
gives theoretical bounds for how much compression can be achieved using lossy compression methods
Rate-distortion function D(R) give the min. achievable average distortion D when source is described using R bits per source symbol
Gaussian source D(R)=2^(-2R)
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R/D for Multiple Description Rate-distortion for multiple description
Single- and multiple-description upper bound can not be achieved simultaneously
Trade-off curve is known only for Gaussian source
Refer to L. Ozarow. “On a Source Coding Problem with Two Channels and Three Receivers,”
No obstacle to practical exploration Growing literatures on practical schemes
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MD Speech and Audio Coding
Sequence of packets and sensitive to loss
Frame even/odd samples coded and sent in separate packets
Path diversity: Independently of the neighboring frame reduce burst loss
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MD Image Coding
Source coding + FEC
MD-FEC Scalable, prioritized nonprioritized
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subsamplingsubsampling
transform transform codingcoding
MD-EFC
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MD-FEC(2) Flexibility
Any number of scalable layers Various amounts of FEC per layers Arbitrary number of descriptions
Refer to R. Puri and K. Ramchandran. “Multiple Description Source Coding Using Forward Error Correction Codes”
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MD Video Coding Consecutive video frames similar Predictive coding
Two design extremes Maintain good quality even when half data is
lost Accomplished independent prediction loops
Maximize coding efficiency Single prediction loop Mismatch with subsequent error propagation
Trade-off between coding efficiency and resilience to full or partial loss of stream
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MD Video Coding(2) Refer to B. Heng, J. G. Apostolopoulos, and J.
S. Lim. “End-to-End Rate-Distortion Optimized MD Mode Selection for Multiple Description Video Coding,”
Small number of description streams Scalable MD coding(i.g. MD-FEC)
Large number of description streams
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Repairable MD Coding Error propagation in predictive coding Repairable MD coding attempt to stop
error propagation repairs one description using
uncorrupted frames from the other description as long as not all the descriptions are simultaneously lost
Complemented with path diversity
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Repairable MD Coding
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Outline Introduction Path Diversity Multiple Description Coding Issues on Systems Design, Analysis Issues on Systems Design, Analysis
and Operationand Operation Applications and Architectures Summary
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Issues on System Design Joint and disjoint paths
Multiple paths maybe independent bottlenecks occur on shard portion impact Identify bottlenecks and avoid them
How many paths to use Specifics of the application
Repairable MD coding, two paths enough Benefits that one is trying to exploit
number of paths increase, aggregated bandwidth increases, probability of outage decrease and delay variability decrease
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Issues on System Analysis Characteristics of the available paths
Select the best paths or best servers Min. distance while max. path diversity
Model path diversity performance Goal
Select the best subset of possible servers Select the best subset of paths Compare path diversity scenarios
One distortion model for MD with two path diversity
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State Transition Pro. Model
00: two descriptions are correctly received01/10: one description is correctly received11:two descriptions are lost simultaneously
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One Path Diversity Model Simplify network topologies
Refer to J. G. Apostolopoulos, W. Tan, S. J. Wee, and G. W. Wornell. “Modeling Path Diversity for Multiple Description Video Communication,”
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Issues on System Operation Streaming and packet scheduling
across asymmetric paths Path measurement
Estimate the characteristics of each path, i.g. time-varying, available bandwidth, etc.
Rate adaption Packet scheduling
More important packet may be sent over the path with lower packet loss rate
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Outline Introduction Path Diversity Multiple Description Coding Systems Design, Analysis and
Operation Applications and ArchitecturesApplications and Architectures Summary
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Low-delay application Low-delay applications(i.g. VoIP)
Choose a low-latency path Skype using nodes in internet to bypass
firewall and NATS
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CDN Using multiple paths simultaneously
Content delivery networks Choose a good/best server by multiple
path selection Multiple servers provide path diversity
with SD and FEC Multiple resources stream packets to client
MD-CDN design and operation Refer to W. Tan et al. “On Multiple Description
Streaming with Content Delivery Networks”
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P2P Peer-to-Peer networks
One essential challenge Provide an uninterrupted flow of data to each
client for the duration of the streaming session
Multiple servers reduce service outages in the face of uncertain peer and network condition
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Wireless network Path diversity over wireless network
Characteristics of wireless network Time-varying and unpredictable behavior
caused by multiple users, interface, propagation effects and mobility
Reduce uncertainty and improve reliabilities
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Architectures Control packet routes
Relay host Direct different streams over different paths
to send each stream to different relay hosts Forward streams to their final destinations
Source routing Specify the set of nodes for each packet to
traverse Specify different source routes for different
subsets of packets
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Outline Introduction Path Diversity Multiple Description Coding Systems Design, Analysis and
Operation Applications and Architectures SummarySummary
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Summary Provide a survey of the benefits,
architecture, system design issues and open problems associated with streaming delivery using path diversity
Path diversity Overcome dynamic and unpredictable
available bandwidth, delay and loss rate Take a step closer to feedback-free video
streaming VoIP, CDN, P2P,WLAN, ad-hoc, etc.
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Summary(2) Multiple description coding
Combined with path diversity to enhance its benefits for media streaming
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References• J. G. Apostolopoulos, W. Tan, S. J. Wee, and G. W. Wornell.
“Modeling Path Diversity for Multiple Description Video Communication,” IEEE ICASSP, May 2002.
• R. Puri and K. Ramchandran. “Multiple Description Source Coding Using Forward Error Correction Codes,” IEEE Asilomar Conference on Signals, Systems, and Computers, October 1999.
• J. G. Apostolopoulos, W. Tan, S. J. Wee, and G. W. Wornell. “Modeling Path Diversity for Multiple Description Video Communication,” IEEE ICASSP, May 2002.
• L. Ozarow. “On a Source Coding Problem with Two Channels and Three Receivers,”Bell Syst. Tech. J., 59:1909–1921, December 1980.
• J. G. Apostolopoulos, T. Wong, W. Tan, and S. J. Wee. “On Multiple Description Streaming with Content Delivery Networks,” IEEE INFOCOM, June 2002.
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Questions and Comments?Questions and Comments?
Thank youThank you