An Improvement in the Pointer Coding of LZ77 Data Compression Method.

There are essentially two approaches in the Ziv- Lempel code to be used in the data compression. They have already been proposed also as the improvements of the Ziv-Lempel code, which can be considered as combinations of the two methods. This paper shows that by executing the combination, not only are advantages produced, but also the structure of the Ziv-Lempel code is derived which realizes a more efficient coding. A precise data compression method is proposed based on the derived structure. The proposed method corresponds to an improvement of the LZ77 method. As the pointer information for the substrings for the coding the parameter corresponding to the length of the substring is encoded first, in contrast to most of the past methods. Then, utilizing the result the coding method for the position of the reference substring is adjusted selectively. The proposed method is one method with the highest compression ability among the modifications of the Ziv- Lempel code. [ABSTRACT FROM AUTHOR]