DATA COMPRESSION USING THE LEMPEL-ZIV-WELCH DYNAMIC DICTIONARY SCHEME

Abstract

This report focuses on the development a computer application program for data compression using the Lempel-Ziv-Welch (LZW) Dynamic Dictionary Scheme. The uncompressed media data such as text, audio, graphics, image and video often require high transmission bandwidth and considerable storage capacity. To provide a feasible and cost-effective solution for the current data storage requirement, compressed data are stored. LZW Dynamic Dictionary Scheme exploits the advantage of repetition of strings in the input stream for data compression. Different dictionary sizes of 10, 11, 12, 13, 14, 15, and 16 bits are used for data compression in this research. The American Standard Code for Information Interchange (ASCII) code is used to assign codes for single characters in the dictionaries while the "xor" type hashing function is used to form array addresses for groups of bytes. Compression ratios for different types of input data are computed and the variation in compression ratio with dictionary size is investigated to determine the optimum dictionary for data compression.