Patent ID: 7263204

Claim:
A method for inserting watermark information B(b 0 ,b 1 , . . . ,b w−1 ,b w ∈ {0,1}, 0≦w≦W−1) for each input vector x t (0≦t≦T−1) of a vector-quantized source image using codeword grouping, the method comprising: a step 1 - 1 of generating three groups G −1 , G 0 and G 1 that satisfy relationships C=G −1 ∪G 0 ∪G 1 and G −1 ∩G 0 =G 0 ∩G 1 =G −1 ∩G 1 =φ and a condition that a codeword c j corresponding to a codeword c i belonging to the group G 0 or G 1 , must belong to the group G 1 or G 0 , for the whole set C of codewords constructing a codebook; a step 1 - 2 of initializing variables t and w to be processed; a step 1 - 3 of selecting one bit b w of the watermark information B; a step 1 - 4 of selecting a codeword c t ; that is the closest to x t from the codebook; a step 1 - 5 of judging a group G p including the selected c i , incrementing t by 1 when P is −1, and returning to the step 1 - 4 ; a step 1 - 6 of allocating the codeword c i without any change when the integer value of the current watermark bit b w is identical to P and allocating the codeword c j corresponding to c i when it is not identical to P, in the case where P is judged to be 0 or 1 from the judgment of the group G p including the selected c i ; and a step 1 - 7 of finishing processing of the watermark when the watermark information B has been completely processed, and respectively incrementing the variables w and t by 1 when it has not been completely processed and then returning to the step 1 - 3 .