Differential coding method and an apparatus therefor

摘要

The differential coding apparatus comprises a delay unit for storing an adjacent value, a transmission value conversion unit for assigning a transmission value to a value of difference between the value to be coded and the adjacent value in the ascending order of the absolute value of the difference value, and a variable-length coding device for assigning a code in the order that the code is increasing in code length as the transmission value increases in number. In the range in which positive and negative difference values exist, positive and negative numbers are alternately given to difference values in the order in which the difference value is increasing in distance from a center difference value of 0. In the range in which either positive or negative difference value exists, serial numbers are successively given to difference values in the order in which the difference value is increasing in distance from the difference value of 0. Then codes are assigned in the order of their increasing in code length to the difference values in the order of the given numbers of transmission values.