Image decoding apparatus

摘要

Bitstream analyzing unit 111 fetches a coded block pattern and a coded quantized DCT coefficient from each block in a bitstream. Entropy decoding unit 112 decodes the coded block pattern into a block pattern and decodes the coded quantized DCT coefficient into pairs of a run length and an effectiveness factor. Dequantization unit 115 generates orthogonal transformation coefficients from the pairs of a run length and an effectiveness factor. Inverse Discrete Cosine Transform (IDCT) unit 110 generates a difference image from the orthogonal transformation coefficients. Decode controlling unit 110 instructs first selecting unit 118 to select constants "0"output from first constant generating unit 117 when the image is a "skipped" block. Image storage unit 120 stores a plurality of reference frame pictures having been decoded. Image restoring unit 119 restores an original block by adding a decoded difference image to a reference block read from the reference frame pictures stored in the image storage unit 120.