Hi Larry and Sampo,
So it turns out that I did misunderstand the original paper. Spectral motif was used for two different things and I simply mixed them up. In the paper, H’(w) did refer to the derivative of H(w): if the amplitude of a signal is changing linearly with a factor alpha, ex: x(t) = h(t)(Amplitude + alpha * t), the FFT of x(t) will be: X(w) = Amplitude * H(w) + i * alpha * H’. (This formula is mentioned in the book “Discrete-Time Signal Processing” from Schaefer if you are interested in learning more about it). In case h(t) is real-symmetrical, H(w) is even-symmetrical and H’(w) is real odd-symmetrical. So to calculate X(w), I just need to store the positive frequency, as H(-w) = H(w), H’(-w) = -H’(w) Still really appreciate all your replies. I’ve learnt something new from your answers. Cheers, MF -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
