Patent ID: 8081678

Claim:
A decoding method for decoding a coded stream on a block-by block basis, comprising: obtaining, from the coded stream, information indicating whether an inverse orthogonal transformation size of a block on which inverse orthogonal transformation should be performed is a first size or a mixture of the first size and a second size, wherein the first size is smaller than the second size; deriving the inverse orthogonal transformation size of the block on which inverse orthogonal transformation should be performed, based on the information included in the coded stream; variable length decoding coded data included in the coded stream to obtain transform coefficients of each block; inverse quantizing the transform coefficients using a quantization matrix corresponding to the derived inverse orthogonal transformation size; and inverse orthogonal transforming the inverse quantized transform coefficients of each block, based on the derived inverse orthogonal transformation size; wherein, in the case where the size information indicates that the inverse orthogonal transformation size of the block on which inverse orthogonal transformation should be performed is a mixture of the first size and the second size and said deriving further includes deriving the inverse orthogonal transformation size based on a motion compensation block size, which is used to perform motion compensation on the block on which inverse orthogonal transformation should be performed, is smaller than the second size, a subsequent inverse orthogonal transforming is performed using only the first size as the inverse orthogonal transformation size.