1. A method of storing fingerprints identifying audio-visual media signals in a database, the method comprising, for each audio-visual signal, the steps of: dividing said audio-visual media signal into a sequence of frames; sub-sampling said sequence of frames by a factor M to obtain a sub-sampled sequence of frames; extracting, for each frame of said sub-sampled sequence of frames, a hash word representing a perceptually essential property of the signal within said frame, to obtain a respective sub-sampled sequence of hash words; storing said sub-sampled sequence of hash words as fingerprint in said database.