Patent ID: 8885707

Claim:
An image decoding apparatus which decodes an image coded signal which is generated by dividing an image into one or more blocks and then coding the one or more blocks, said image decoding apparatus comprising: an extraction unit configured to extract, from the image coded signal, intra-prediction mode information that indicates which intra-prediction mode among a plurality of intra-prediction modes is used to intra-code a current block; a reference pixel determination unit configured to determine whether or not the intra-prediction mode information has an error by determining whether or not a reference block necessary for the intra-prediction mode indicated by the intra-prediction mode information exists in one of (i) a picture including the current block and (ii) a slice including the current block; and an intra image decoding substitute unit configured to switch the intra-prediction mode to another intra-prediction mode, and generate a decoded image of the current block using the other intra-prediction mode, when said reference pixel determination unit determines that the necessary reference block does not exist in one of the picture including the current block and the slice including the current block.