The methods of improving the compression ratio of LZ77 family data compression algorithms

In a multimedia system, one is required to handle, store and transmit a lot of data. We consider lossless data compression proposed by Lempel and Ziv (1977). We review the various methods and techniques of improving the compression ratio of the LZ77 scheme, and write a compression program to get a 3.14 times compression for various file styles by using these methods. In English text, the LZ77 optimal algorithms of LZ77 can achieve a compression efficiency of about 2.5 bits per character, however the entropy of English text is about 1.3 bits per character, so we can compress the data further. Another way of improving compression ratio is by arithmetic coding.