Patent ID: 6915000

Claim:
A system for inserting an electronic watermark data comprising: DCT converter for extracting a block of k×k pixels from an original image, subjecting said block to DCT (discrete cosine transform), and then outputting data after the DCT conversion; quantizer for quantizing DCT coefficients output from said DCT converter; movement decision means for deciding the magnitude of a movement based on a generation amount from said DCT converter; picture-type decision means for deciding a picture type; an electronic watermark data table for storing first to j-th electronic watermark data, each of said first to j-th electronic watermark data having two values depending on the magnitude of a movement, one value corresponding to low movement and the other corresponding to high movement, when the movement value is compared with a threshold value and said movement is based on a generation amount from said DCT converter, for each picture type; electronic watermark data selector for selecting said electronic watermark data of one type according to said picture type and said movement; and electronic watermark data inserter means for inserting said selected electronic watermark data into data after said DCT conversion; whereby the magnitude of a movement is decided by obtaining a difference between a DCT coefficient of a front frame and a DCT coefficient of a rear frame and electronic watermark data with a suitable strength is inserted according to the magnitude of said movement.