Software and Hardware Enhancement of Arithmetic Coding

Arithmetic coding utilizes the skewness of character distribution by assigning larger intervals (code ranges) to characters having higher probabilities of occurrence. In this paper, we present a scheme to enhance arithmetic coding by utilizing the locality of character reference, i.e., the tendency of consecutive characters to fall within the same type (e.g., alphabets, digits, trailing blanks, successive zeros). The proposed scheme effectively increases the code ranges of individual characters by splitting the interval assignment into different groups. This will decrease the rate of interval narrowing and hence improve the compression efficiency. The paper is concluded by giving the VLSI design of the modified arithmetic coding scheme. Successful VLSI compression chips would be a significant enhancement to the technology of data encoding and would greatly contribute to reducing the cost of data transmission and data access within statistical database systems.