Patent ID: 6920176

Claim:
An image decoding device, which decodes in target macro block units, coded image signals that are coded by DCT, quantization, and variable-length coding, comprising: a target macro block setting means for setting a target macro block to be decoded currently from among an entire image to identify a target macro block; a target macro block extraction means for performing a variable length decoding process and a zigzag scan on said coded image signal and extracts data of said target macro block to produce an extracted target macro block data, a prediction means for performing a DC/AC prediction process on said extracted target macro block data, an inverse quantization means for performing inverse quantization on said target macro block data that have been subject to said prediction process, and an inverse DCT means for performing inverse DCT on said target macro block data that have been subject to inverse quantization and outputs an image of said target macro block; said prediction means includes a reference value storage means; said reference value storage means including means for holding reference values that are necessary for said prediction process performed on said target macro block; a prediction computation means for performing prediction computation based on reference values of said reference value storage means; a predicted value storage means for holding results of said prediction computation; a prediction control means for controlling said reference value storage means, said prediction computation means, and said predicted value storage means; and a total storage volume of said reference value storage means and said predicted value storage means is smaller than a storage volume of predicted values for an entire image size, and said prediction control means includes means for copying data, necessary for said prediction computation of a next target macro block, from said predicted value storage means to said reference value storage means.