IMAGE DECODER AND IMAGE DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To obtain an MPEG down-decoder where deterioration in image quality due to an inter-image is eliminated. SOLUTION: A reduced inverse discrete cosine transform device 14 executes 4×4 reduction IDCT to MPEG data when a DCT mode is in a field mode. A reduced inverse discrete cosine transform device 15 executed IDCT to all coefficients of a DCT block when the DCT mode is in a frame mode and an image is an intra-image to separate the block into two pixel blocks corresponding to interlace scanning and executes DCT to the two separated pixel blocks respectively. A reduced inverse discrete cosine transform device 16 a executes 4×4 reduction IDCT to MPEG data when the DCT mode is in a frame mode and an image is an inter-image.