Abstract: The invention provides a picture data decompression apparatus which reduces the time required for decompression of picture data and operates at a high speed. The picture data decompression apparatus includes a module switching section for extracting code patterns in units of n bits the compressed picture data, m decoding and dequantization modules, and an inverse orthogonal transform section for inverse orthogonal transforming decoded and dequantized data from the m decoding and dequantization means. Each of the decoding and dequantization modules decodes and dequantizes, from a code pattern in units of n bits extracted by the module switching section, only a predetermined variable length code of a single unique code pattern of n bits from among m different predetermined patterns.

Abstract: In a data-compression of a moving picture employing MPEG system, the quantization step used for quantizing coefficients of frequency components obtained in DCT (discrete cosine transform), is determined on a first frame of the moving picture, and is used for all the frames of the moving picture. A frame is processed by first run of data-compression. Code volume is allotted for each block in accordance with data obtained by the first run of data-compression, and in second run of data-compression, Huffman coding is discontinued when generated code volume of a block becomes larger than the code volume allotted to the block. When generated code volume of a frame is smaller than the target code volume of a frame, the surplus target code volume is added to a target code volume of a succeeding frame.