Patent ID: 6823074
Filing Date: 2004-11-23
Classification: G06T,H04N

Abstract:
A digital-watermark superposing apparatus for superposing on video data a digital watermark which bears information different from the video data, comprising:a DCT circuit for generating a plurality of DCT coefficients for respective frequency components by subjecting the video data to a two dimensional DCT transform for each pixel block consisting of a predetermined number of pixels; a quantizer for quantizing a value of at least one of the DCT coefficients in accordance with a quantization rule corresponding to the information so as to obtain a quantized DCT coefficient, wherein the quantizer quantizes the DCT coefficient by a step size larger than an original quantization step size; and an inverse DCT circuit for performing a two-dimensional inverse DCT transform with respect to the DCT coefficients in which the at least one DCT coefficient thereof is replaced with the quantized DCT coefficient, so as to obtain digital watermark superposed video data in which the digital watermark corresponding to the information has been superposed on the video data.