Patent ID: 8762146

Claim:
A system, comprising a processor to define a plurality of opportunities for encoding a watermark into an audio stream, the audio stream having a plurality of sections, each of the sections, when represented in the frequency domain, including a signal of amplitude against frequency, the processor being operative to, for each one of the sections of the audio stream: identify a fundamental frequency, f, of the one section, the fundamental frequency being the frequency with the largest amplitude of the signal in the one section, the fundamental frequency f defining a plurality of harmonic frequencies, each of the harmonic frequencies being at a frequency f/2n or 2fn, n being a positive integer; and define the one section as an opportunity for encoding at least part of the watermark if the amplitude of the signal of the one section is less than a value v for all frequencies in one or more of a plurality of different frequency ranges, each of the different frequency ranges being centered around different ones of the harmonic frequencies.