code: def s2dctmat(nfilt,ncep,freqstep):
      
      melcos = numpy.empty((ncep, nfilt), 'double')
      for i in range(0,ncep):
          freq = numpy.pi * float(i) / nfilt
          melcos[i] = numpy.cos(freq * numpy.arange(0.5, float(nfilt)+0.5, 1.0, 'double'))
      melcos[:,0] = melcos[:,0] * 0.5
      return melcos
docs: Return the 'legacy' not-quite-DCT matrix used by Sphinx