Patent ID: 7295609

Claim:
An image information decoding method for decoding compressed image information which has been coded via a process including the steps of dividing an input image signal into blocks, performing an orthogonal transform on the blocks on a block-by-block basis, and quantizing resultant orthogonal transform coefficients, said decoding process including the steps of performing dequantization and performing an inverse orthogonal transform, wherein, in the dequantization, weighted dequantization is performed on each luma and chroma components of the quantized coefficients by an addition operation on a quantization parameter, an array B(QP) consisting of elements having values which increase or decrease by β % with increasing of the value of the parameter QP by 1 is used as the sequence of numbers corresponding to the quantization step sizes, the dequantization is performed by multiplying the quantized coefficients by the values of the array B(QP), the ratio β % is 12%, and the values of the elements of the array B(QP) increase by 12% with increasing of the value of the parameter QP by 1.