Patent ID: 6477276
Filing Date: 2002-11-05
Classification: G06T,H04N

Abstract:
A digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:band division means for dividing said digital image signal into transform coefficients over a plurality of frequency bands using either a discrete wavelet transform or sub-band division; block division means for dividing the lowest frequency band out of said plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size; quantization means for calculating a mean value M of the transform coefficients for each of said blocks, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q, wherein Q is an integer of not less than one, to calculate a quantization value; signal replacement means for replacing the quantization value, for each of said blocks, and on the basis of said quantization value and the value of said digital information to be embedded which correspond to the block; mean difference addition means for subjecting said replaced quantization value, for each of said blocks, to inverse linear quantization using said quantization step-size Q to calculate a mean value Mâ€², and for adding a difference DM, wherein DM=Mâ€²âˆ’M, between the mean value Mâ€² and said mean value M to all the transform coefficients in each block; mean calculation means for calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of said difference DM; and band synthesis means for reconstructing a digital image signal in which said digital information has been embedded using the lowest frequency band after the addition of said difference DM and the other frequency bands.