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