Differential coding method and apparatus.

摘要

A differential coding apparatus comprises a delay unit (31) for storing an adjacent value (P) to the value (X) to be coded, a transmission value conversion unit (34) for assigning a transmission value (Y) to the value of a difference (D) between the value to be coded (X) and the adjacent value (P) in the ascending order of the absolute value of the difference value (D), and a variable length coding device (35) for assigning a code in the order that the code is increasing in code length as the transmission value (Y) increased 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 centre 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 (D) in the order of the given numbers of transmission values (Y). The corresponding coding method is also described.