specgen.py

def SpecGen(self, filepath):
        """
        Code to generate spectrogram adapted from code posted on https://mail.python.org/pipermail/chicago/2010-December/007314.html by Ken Schutte ([email protected])
        """

        sr, x = scipy.io.wavfile.read(filepath)
    
        ## Parameters
        nstep = int(sr * self.specNStepMod)
        nwin  = int(sr * self.specNWinMod)
        nfft = nwin

        # Get all windows of x with length n as a single array, using strides to avoid data duplication
        #shape = (nfft, len(range(nfft, len(x), nstep)))
        shape = (nfft, ((x.shape[0] - nfft - 1)/nstep)+1)
        strides = (x.itemsize, nstep*x.itemsize)
        x_wins = np.lib.stride_tricks.as_strided(x, shape=shape, strides=strides)
    
        # Apply hamming window
        x_wins_ham = np.hamming(x_wins.shape[0])[..., np.newaxis] * x_wins
    
        # compute fft
        fft_mat = np.fft.fft(x_wins_ham, n=nfft, axis=0)[:(nfft/2), :]
    
        # log magnitude
        fft_mat_lm = np.log(np.abs(fft_mat))
    
        return fft_mat_lm.T