IMAGE CODER AND IMAGE DECODER

摘要

PROBLEM TO BE SOLVED: To attain information compression with higher efficiency by allowing an inverse quantization section to use an optional value from a minimum value to a medium in a quantization step for an inverse quantization value so as to suppress a quantization error. SOLUTION: An input image signal is given to a conversion section 101, in which signal conversion such as discrete cosine transformation or sub band division is applied and quantized by a quantization section 102. A coefficient signal quantized is divided into blocks by a block processing section 103 and subject to variable length coding by a variable length coding section 104 in the unit of blocks. The coded code word is given to a variable length decoding section 105, in which the code is variable-length-coded. Then inverse processing of block processing is applied by an inverse block processing section 106 and inverse-quantization is applied by an inverse quantization section 107. Then an inverse transformation section 108 applies inverse transformation to the discrete cosine transformation or the sub band division and the result is outputted as a decoded image signal. Furthermore, an inverse quantization section 107 uses a value in the quantization step closer to 0 from a median for the inverse quantization value to reduce the quantization error.