QUANTIZED WIDTH ADJUSTING CIRCUIT UTILIZING DCT CONVERSION AC COEFFICIENT

摘要

PURPOSE: To improve the S/N ratio by classifying an image into numerous blocks, applying DCT(discrete cosine transformation) processing to each block, using an AC value so as to make a quantization width variable depending on a degree of complicatedness of an image. CONSTITUTION: A DCT 10 receiving data subject to block formatting provides outputs of DC and AC coefficients. The absolute AC coefficient is given to an accumulator 30 and the accumulated coefficient is given to a scaling factor decision section 40, in which complicatedness of an image of each block is decided. The scaling factor depending on the complicatedness of the image being an output of an encoder 44 is applied to a quantization width decision section 50, in which the quantization width is decided. Furthermore, data processed by the DCT 10 are given sequentially to a shift register 70 and a linear quantization section 80 receiving shifted data quantizes the data by the quantization width decided by the decision section 50. Thus, the S/N ratio is improved and the hardware is simplified.