FRE 2672

07/09/2005

Distributed Source Coding of

Still Images

Ç. Dikici,R. Guermazi, K. Idrissi, A.Baskurt

LIRIS, UMR 5205 CNRS

INSA de Lyon, France

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Agenda

Distributed Coding

System Architecture

Encoding and Decoding of Images

Experiments

Conclusion

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Motivation

Coding of multiple sources which can not communicate at the encoder

Ultra-low encoding complexityReduce power consumption

Ex: Image and Video coding, sensor networks

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Theoretical Limits

Encoder XEncoder X

Encoder YEncoder Y

X

Y

Joint EncoderJoint Encoder

R ≥ H(X,Y)

H(X,Y)=H(X)+H(Y)-I(X,Y)

JointDecoder

JointDecoder

X,Y

R(X) ≥H(X|Y)

R(Y) ≥H(Y|X)

R(X)+R(Y) ≥H(X,Y)

R(X) ≥ H(X)

R(Y) ≥ H(Y)

R(X)+R(Y) ≥H(X)+ H(Y)

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Literature and Our ContributionsSlepian&Wolf[1973], Wyner&Ziv[1976]

Video Coding: Ramchandran et al.[99], Girod et al.[99]

Image coding: ?

ContributionA new still image coding based on Distributed Source

Coding using the wavelet domain

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Wyner Ziv Scheme adapted to

Image Coding

Coarse encodingCoarse encoding

Side InformationSide Information

X

Y

JointDecoding

JointDecoding

X

cosets

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Overall System

Quantizer

CosetConstruction

WaveletComposition

I ParameterEstimation

1I

2I

Entropy coding

Entropy coding

Ch

an

ne

l

Entropy decoding

Entropy decoding

Modulo encoding

Coset Boundaries

WaveletDecomposition

SI Update Refinement

I

LL HL

LH HH

HHLH

HL

LL 0

0 0

0 00 0

0 00 0

0 00 0

Only LL is transmitted

Modulo coding DXX ii mod)( 1

Iterative decoding

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Experimental Results

28 DB 34.1DB 35DB

SI SI+Coset SI+Coset (with refinement)

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Conclusion and Future Work

Proposition of DSC based image coding scheme Low-pass wavelet coefficients and modulo binning of the

image are encoded parallel, decoded jointly Edge features of the image recovered

Very first rate&distortion results are not satisfactoryReduction of the computational complexity of the coder

LDPC or Turbo Codes for coset creationDefinition of the side information

A map of ROI Global and local features (color, texture, shape, contour,..)

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Question&Answers