ENCODER, DECODER, DEVICE FOR ENCODING AND DECODING, ENCODING METHOD AND DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To reduce a total code length and a code output time by allowing an encoder to ignore one of partial areas obtained by equally dividing an effective area indicated by a carry detector to a high order and a low order so as to update the effective area. SOLUTION: An arithmetic encoder 13C executes encoding arithmetic by means of a C register 30A and an A register 31 from the inputs of an LSZ value 9 and a binary symbol 14, measures the code outputting timing of a byte unit by a CT counter 50 and judges the presence/absence of a carry boundary in an area from a T register 61 and an R0 register 63 synchronizing to the time of outputting a code. Then, when the carry boundary exists, the encoder 13C forcedly defines the presence/absence of carry by correcting the C register 30A and the A register 31 by applying a 1/2 area ignoring system, executes carry propagation until a maximum BUFFER 51 to execute defined encoding output, and outputs a code 4C. Thus, one of partial areas obtained by equally dividing an effective area indicated by a carry detector to a high order and a low order like this is ignored to update the effective area.