Better OPM/L Text Compression |
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Authors: | Bell T |
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Affiliation: | University of Canterbury, New Zealand; |
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Abstract: | An OPM/L data compression scheme suggested by Ziv and Lempel, LZ77, is applied to text compression. A slightly modified version suggested by Storer and Szymanski, LZSS, is found to achieve compression ratios as good as most existing schemes for a wide range of texts. LZSS decoding is very fast, and comparatively little memory is required for encoding and decoding. Although the time complexity of LZ77 and LZSS encoding isO(M)for a text ofMcharacters, straightforward implementations are very slow. The time consuming step of these algorithms is a search for the longest string match. Here a binary search tree is used to find the longest string match, and experiments show that this results in a dramatic increase in encoding speed. The binary tree algorithm can be used to speed up other OPM/L schemes, and other applications where a longest string match is required. Although the LZSS scheme imposes a limit on the length of a match, the binary tree algorithm will work without any limit. |
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