Patent ID: 8281137

Claim:
A method for determining whether or not a reference pattern is present in a possibly watermarked signal which was received using a microphone, wherein at least one candidate reference pattern possibly matching said reference pattern is correlated with said received watermarked signal and corresponding correlation result amplitude peaks are checked, said method comprising: calculating for a current section of said received signal the correlations with each one of said reference patterns; finding within the correlation result amplitude values groups of values in which the absolute value of a current correlation result amplitude value—denoted main peak—is greater than a first threshold and that absolute value of said main peak is also greater than the absolute value of its left neighbor correlation result amplitude value and is also greater than the absolute value of its right neighbor correlation result amplitude value; finding, within a predetermined vicinity of each one of said main peaks, further peaks for each of which the absolute value of a current correlation result amplitude value is greater than a second threshold smaller than said first threshold and for each of which further peaks its absolute value is also greater than the absolute value of its left neighbor correlation result amplitude value and is also greater than the absolute value of its right neighbor correlation result amplitude value; combining, for each one of said groups of values, the absolute values of said main peak and said further peaks, thereby forming a sum value per group; for each one of said reference patterns, determining the maximum one of said group sum values wherein, when the largest one of these maximum values exceed a predetermined or variable threshold, deciding that a corresponding reference pattern is assumed to be present in the received signal.