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Wavelet-based Entropy Measure for Rate-Distortion Optimization in Image Coding

Garcia-Alvarez J., Führ H., Castellanos-Dominguez G.

International Journal of Electronics and Telecommunications

2010

Vol. 56, No. 1

25-31

A novel method for calculation of the entropy measure in wavelet space is proposed. This perceived-based entropy measure uses a Second Order Model entropy estimator, in which the occurrence of neighbors is considered in formulation. It has the intention to allow the implementation of a more suitable measure in coding processes and a relationship between the metric and the description of perceptual features. This method is used for the Rate-Distortion optimization in order to improve the bit-allocation coding algorithm, demonstrating that the wavelet-based entropy estimates a truncation step close to the target rate. The hypothesis is founded in the effect of distortion on the coefficient allocation. Because entropy measure is a close approximation of the conditional probability of image in multiresolution space, it provides an adequate representation for the information of a Detail feature. A definition of Detail-based homogeneity variance criteria is used for the information quantity - wavelet representation space, in order to find the image that fits a given Quality Level criteria. Experimental results are obtained for artificial and natural databases.

Experimental rate distortion analysis of image coder with contourlet transform and SPIHT algorithm

Głomb P., Nowak S., Nowak S.

Theoretical and Applied Informatics

2008

Vol. 20, No. 3

215-225

We analyze the results of a series of experiments to investigate the empirical rate distortion performance of a contourlet image coder. We use a contourlet transform with different number of directional decomposition levels, with wavelet transform as a reference; coefficients are coded with the SPIHT algorithm. The experimental setting uses popular test images (‘Lena’, ‘Peppers’ etc) and broad spectrum of quality measures (MSE, PSNR, measures dedicated to quantization degradation and structural similarity). We conclude that within the range of analyzed parameters contourlet transform outperforms wavelets in terms of quality, but because of high computational cost, the gains may not easily translate into overall increased performance.

W artykule badana jest wydajność, wyrażona jako liczba bitów na współczynnik (bpc - bits per coefficient) dekompozycji obrazów metodą konturkową. Eksperymenty prowadzone były dla różnych poziomów kierunkowych dekompozycji. Wyniki porównywane są z wynikami uzyskanymi dla transformaty falkowej. Współczynniki uzyskane w wyniku dekompozycji kodowane są za pomocą algorytmu SPIHT. Przyjęta miara (bpc) pozwala na bezpośrednie porównanie tych dwóch metod dekompozycji.