Patent ID: 8041073

Claim:
A method for decoding watermark data information from a watermarked audio or video signal on which said watermark data information was modulated, using correlation with a pre-determined data sequence, said method performed by a processor, comprising the steps: receiving a section of said watermarked audio or video signal; correlating said section with at least one pseudo-random sequence; deriving from the correlation result or results, respectively, said watermark data information, wherein said correlations are carried out in the frequency domain and wherein bins of the resulting spectrum or spectra for said section are set to zero which do not have an impact on forming a peak at location zero in said correlation result or results, followed by inversely transforming the such processed spectrum or spectra into the time domain, wherein said correlation is performed using a one-dimensional real-symmetric fast Fourier transform in which, to said section representing a first transformed vector and having N values and to said pseudo-random sequence representing a second transformed vector having N values, N−1 zeroes are attached, and wherein one of said transformed vectors is multiplied by the conjugated version of the other transformed vector in order to form said correlation in the frequency domain, and wherein said inverse transform is an inverse one-dimensional real-symmetric fast Fourier transform.