Arithmetic decoding device, arithmetic coding device, image decoding apparatus, and image coding apparatus
A coefficient presence/absence flag decoding unit, included in a quantized residual information decoding unit which reduces a processing amount related to coding and decoding of a transform coefficient, splits a target frequency domain or a target pixel domain into sub-blocks, and derives different context indexes with respect to each transform coefficient in a pixel domain, obtained through a transform skip or a transform/quantization bypass, and each transform coefficient which is obtained for each frequency component through frequency transform.
1. An arithmetic decoding device which decodes coded data of each transform coefficient which is obtained by performing frequency transform on a target image for each unit domain and each transform coefficient obtained through a transform skip or a transform/quantization bypass, the device comprising:
a context index deriving circuit that derives a context index of a non-zero transform coefficient presence/absence flag indicating whether or not the transform coefficient is 0 in a unit domain; and
a syntax decoding circuit that arithmetically decodes the non-zero transform coefficient presence/absence flag by referring to the derived context index,
wherein the context index deriving circuit derives a context index common to non-zero coefficient presence/absence flags corresponding to transform coefficients obtained through the transform skip or the transform/quantization bypass.