Patent ID: 7131007
Filing Date: 2006-10-31
Classification: G10L

Abstract:
1. A computer-implemented method of retrieving a watermark in a watermarked signal, the watermarked signal comprising odd and even overlapped blocks where the watermark is contained in even blocks, the method comprising, for each k-th block: subtracting odd blocks from a k-th block of the watermarked signal to generate {overscore (s)}* applying an FFT to {overscore (s)}* calculating a phase of {overscore (S)} calculating the difference Ψ(f) between {overscore (φ)}(f) and φ(f); and using a Viterbi search to retrieve the watermark embedded in Ψ(f), wherein if during a phase-modulation stage of generating the watermarked signal, the result of adding a phase-modulation to the phase of the original signal has an absolute value greater than π, then the method further comprises: unwrapping Ψ(f) to obtain a correct phase modulation {tilde over (Φ)} using the Viterbi search to retrieve the watermark embedded in {tilde over (Φ)}