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Path Diversity for Media Path Diversity for Media Streaming Streaming The Use of Multiple Description Coding The Use of Multiple Description Coding J. Apostolopoulos, M. Trott and W. J. Apostolopoulos, M. Trott and W. Tan Tan Presented by Xiaoyuan GUO Presented by Xiaoyuan GUO

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Page 1: Path Diversity

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

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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

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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

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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