ABSOLUTE IMAGE QUALITY EVALUATION METHOD USING ELECTRONIC WATERMARK, CODING METHOD FOR IT, AND CODER

摘要

PROBLEM TO BE SOLVED: To provide an absolute image quality evaluation method that can evaluate the image quality of a decoded image by using electronic watermark information even without an original image to be referenced. SOLUTION: A switch section 10 extracts at random a block Bi from an input image signal 1 by the number of DCT coefficients of one block. A DCT section 13 calculates an i-th DCT coefficient FBi[i] and a bit stream processing section 14 converts the DCT coefficient Fbi[i] into a bit stream dk (k=1-11). A watermark imbed section 15 imbeds a low-order 8-bit of the bit stream dk to a high frequency region of a quantization coefficient matrix of an adjacent block as watermark information together with a code bit. A receiver side detects the watermark information by the number of the DCT coefficients of one block, recovers each virtual block on the basis of the detected watermark information and the DCT correction corresponding to the watermark information obtained from a decoded image to estimate the SNR of the decoded image.