<title>Highly efficient entropy coding of multilevel images using a modified arithmetic code</title>

Abstract

ABSTRACT In this paper, firstly we present a modified multiplication-free arithmetic code that can improve theefficiency of the conventional multiplication-free arithmetic code by increasing the numbers of theestimated probability from 2 to 3 in a power unit range. Then, we describe the application of thismodified algorithm to the entropy coding of multi-level images. In our entropy coding scheme, themulti-alphabet symbol string, which is input from the sequence of the zig-zag scanning data obtained by applying the ADCT compression algorithm to the original image, can be directly sent to the encoder,i.e., there is no need to decompose the symbols into a series of binary decisions. Finally, some simulation results will be given to show that good performance can be achieved with our coding scheme. 1 INTRODUCTION Arithmetic codes'112' , developed by Rissanen et ad. about this decade ago, have since then become animportant and efficient entropy coding method. There are two main excellent features of the arithmeticcodes. Firstly, they can be easily used to encode the data strings modeled with both stationary andnonstationary sources even with unknown statistics of the data strings, and secondly, good efficiencycan be achieved by using this code. Moreover, as a method of the arithmetic codes, QM-Coder, hasbeen selected as a source (or entropy) coding method of some international standard schemes of imagecoding, such as JBIG(Joint Bi-level Image Coding Experts Group) and JPEG(Joint PhotographicCoding Experts Group). Therefore it is undoubted that arithmetic codes will become more useful forthe purpose of the image data compression.However, there remains a problem to be solved for the arithmetic codes concerning how to reduce thecomplexity at the minimum sacrifice of the code efficiency. That is also the main objective of thevarious researches done on the arithmetic codes up to now.