Patent ID: 9699479
Date: 2017-07-04
CPC Classifications: H04N

Claim:
1. An arithmetic decoding device for decoding coded data of a transform coefficient obtained by performing frequency transform on a target image for each unit domain, the device comprising: a sub-block coefficient presence/absence flag decoding unit configured to decode a sub-block coefficient presence/absence flag indicating whether or not one or more non-zero transform coefficient are included in each of a plurality of sub-blocks into which the unit domain is split; and a context index deriving unit configured to derive a context index corresponding to a transform coefficient presence/absence flag indicating whether or not the target transform coefficient is 0, wherein in a case where the non-zero transform coefficient is included in a sub-block which is adjacent to the right side of the target sub-block, and the non-zero transform coefficient is not included in a sub-block which is the lower to the target sub-block, (i) the context index deriving unit is configured to derive the context index having a first value in a case where a vertical coordinate indicating a position of the transform coefficient is equal to a first threshold value, (ii) the context index deriving unit is configured to derive the context index having a second value in a case where a vertical coordinate indicating a position of the transform coefficient is equal to a second threshold value, and (iii) the context index deriving unit is configured to derive the context index having a third value in a case where a vertical coordinate indicating a position of the transform coefficient is not equal to the second threshold value.