Patent attributes
A system and method of retrieving a watermark in a watermarked signal are disclosed. The watermarked signal comprises odd and even overlapped blocks where the watermark is contained in the even blocks. The method comprises, for each k-th even block, subtracting the two adjacent odd blocks from the k-th even block of the watermarked signal to retrieve {overscore (s)}*k(n), transforming {overscore (s)}*k(n) into the frequency domain to generate {overscore (S)}k(f), calculating a phase of {overscore (S)}k(f) as {overscore (φ)}(f) and a phase of Sk(f) as φ(f), calculating the difference Ψ(f) between {overscore (φ)}(f) and φ(f), unwrapping Ψ(f) to obtain the phase modulation {tilde over (Φ)}k(f), and using a Viterbi search to retrieve the watermark embedded in {tilde over (Φ)}k(f).
