A method of generating a compressed representation of a source data string.

摘要

An improved method is disclosed for generating a compressed representation of a source data string each symbol of which is taken from a finite set of m + 1 symbols, a0 to am . 'The method is based on an arithmetic coding procedure wherein the compressed representation is recursively generated as successive sub-intervals within a predetermined interval. The width of each sub-interval is theoretically equal to the width of the previous sub-interval multiplied by the probability of the current symbol. The improvement is achieved by approximating the width of the previous sub-interval so that the approximation can be obtained by a single shift and add operation using a suitable shift register.