Issues with scipy.io wave file processing after applying fourier transforms

Question

I\'m working with some audio files in Python using scipy.fftpack and scipy.io packages. What this implies is I have wave files that I am importing, playing around with them

Answer 1

You need to convert your data after processing to an integer type of appropriate bit depth. Using this file as an example:

>>> import scipy.io.wavfile
>>> rate, data = scipy.io.wavfile.read('Happy Tree Friends.wav')
>>> rate
8000
>>> data
array([ 5, -5,  5, ...,  0, -1,  0], dtype=int16)
>>> data_bis = np.fft.ifft(np.fft.fft(data))
>>> data_bis
array([  5.00000000e+00 -1.55406753e-11j,
        -5.00000000e+00 +1.95349676e-11j,
         5.00000000e+00 +1.41131140e-11j, ...,
         8.06674092e-12 -7.58643463e-13j,
        -1.00000000e+00 -2.21611283e-12j,  -2.04999489e-11 +4.55890751e-12j])
>>> data_bis.dtype
dtype('complex128')

Even though the values in data are really close to the ones in data_bis, they are very different beasts, as the following shows:

>>> scipy.io.wavfile.write('test.wav', rate, data_bis)
>>> scipy.io.wavfile.read('test.wav')
TypeError: data type not understood

But if you simply convert your processed results back to the original dtype, everything works nicely again:

>>> scipy.io.wavfile.write('test.wav', rate, data_bis.astype(data.dtype))
__main__:1: ComplexWarning: Casting complex values to real discards the imaginary part
>>> scipy.io.wavfile.read('test.wav')
(8000, array([ 4, -5,  4, ...,  0, -1,  0], dtype=int16))