code: def spectral_flux(d0, d1):
      
      # compute the spectral flux as the sum of square distances:
      d0 = np.mean(d0, axis=1)
      d1 = np.mean(d1, axis=1)
      nFFT = min(len(d0) // 2, len(d1) // 2)
      X = FFT(d0, nFFT)
      Xprev = FFT(d1, nFFT)
  
      # L = min(len(X), len(Xprev))
  
      sumX = np.sum(X + EPSILON)
      sumPrevX = np.sum(Xprev + EPSILON)
      return np.sum((X / sumX - Xprev / sumPrevX) ** 2)
docs: Computes the spectral flux feature of the current frame