ARITHMETIC DECODER, IMAGE DECODER, ARITHMETIC ENCODER, AND IMAGE ENCODER

摘要

PROBLEM TO BE SOLVED: To reduce a processing amount for encoding and decoding a transformation coefficient.SOLUTION: A peripheral reference context deriving unit 124c provided in a coefficient presence/absence flag decoding unit 124 derives a context index to assign to each transformation coefficient presence/absence flag belonging to a target sub-block, on the basis of the number of decoded non-zero transformation coefficients included in a reference area selected on the basis of a scan index indicating the scanning direction of a transformation coefficient.