Patent ID: 7469008

Claim:
An image decoding apparatus for decoding at least a first coded bit stream into which header information of the H.263 coding scheme and image coded data encoded in the H.263 coding scheme are multiplexed, or for decoding a second coded bit stream into which header information of the MPEG-4 coding scheme and image coded data encoded in the MPEG-4 coding scheme are multiplexed, the image decoding apparatus comprising: a setter for setting a quantization scale to be used for an inverse quantization of a direct current component of an intra-DCT coefficient according to the received first coded bit stream and the received second coded bit stream; and an inverse quantization processor for performing an inverse quantization process for the direct current component of the intra-DCT coefficient using the quantization scale set by the setter, wherein when the first coded bit stream is received, the setter sets the quantization scale to eight, and when the second coded bit stream is received, the setter sets the quantization scale according to a quantization step size determined per macroblock.