code: def dct2(input, K=13):
      
      nframes, N = input.shape
      freqstep = numpy.pi / N
      cosmat = dctmat(N,K,freqstep,False)
      return numpy.dot(input, cosmat) * (2.0 / N)
docs: Convert log-power-spectrum to MFCC using the normalized DCT-II