RATE CONTROL OPTIMIZATION IN EMBEDDED WAVELET CODING

(Version: 1.0: REWIC2.HTML v. 1.0 2002/09/12)

Table of Contents

 

Introduction

    REWIC2 is a software-based implementation of the codec specified in the paper "Rate control optimization in embedded wavelet coding" by J.A Garcia et al..
    In an embedded wavelet scheme for progressive transmission, a tree structure naturally defines the spatial relationship on the hierarchical pyramid. Transform coefficients over each tree correspond to a unique local spatial region of the original image, and they may be coded bit-plane by bit-plane through successive-approximation quantizat-ion. After receiving the approximate value of some coefficients, the decoder can obtain a reconstructed image.
    REWIC2 is a rational system for progressive transmission which, in absence of a priori knowledge about regions of interest, choose at any truncation time among alternative trees for further transmission. It is based on a novel mathematical methodology for rate control by organizing the progressive transmission in accordance with coherence constraints for avoiding forms of behavioral inconsistency. A set of postulates are provided for specifying the ways in which preferences need to be made precise and fit together if illogical forms of behavior are to be avoided.
    The rational choice for transmission at any truncation time is to select bit streams which have the maximum expected increase in utility per coding bit, where ``rational'' must be understood in the sense that it cannot lead the transmission system into forms of behavioral inconsistency.
    Thus each spatial region of the image considers only benefits to itself (the maximum expected increase in utility per coding bit) in making the individual choice of a rational strategy for bit allocation. But, self-regarding region might also agree on an allocation of bits which is to be brought about by a joint strategy determining each region's allocation. The question is here: Under what conditions is their agreement rational?.
REWIC2 characterize the collective rationality by a rational agreement of just distribution reducing the inequality in the distribution of benefits among spatial regions.

Examples

The following examples show images encoded/decoded (without entropy coding) using both SPIHT ( Set Partitioning Hierarchical Trees, by Said and Pearlman http://www.cipr.rpi.edu/research/SPIHT/spiht0.html) and REWIC.The images are decomposed by a 6-level 9-7 tap biorthogonal Daubechies filter.


 

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