[FIXED] Error passing wav file to IPython.display

Issue

I am new to Python but I am studying it as programming language for DSP. I recorded a wav file, and have been trying to play it back using IPython.display.Audio:

import IPython.display
from scipy.io import wavfile

rate, s = wavfile.read('h.wav')
IPython.display.Audio(s, rate=rate)

But this gives the following error:

struct.error: ushort format requires 0 <= number <= 0xffff

I tried installing FFmpeg but it hasn't helped.

Solution

That's not a very useful error message, it took a bit of debugging to figure out what was going on! It is caused by the "shape" of the matrix returned from wavfile being the wrong way around.

The docs for IPython.display.Audio say it expects a:

Numpy 2d array containing waveforms for each channel. Shape=(NCHAN, NSAMPLES).

If I read a (stereo) wav file I have lying around:

rate, samples = wavfile.read(path)
print(samples.shape)

I get (141120, 2) showing this is of shape (NSAMPLES, NCHAN). Passing this array directly to Audio I get a similar error as you do. Transposing the array will flip these around, causing the array to be compatible with this method. The transpose of a matrix in Numpy is accessed via the .T attribute, e.g.:

IPython.display.Audio(samples.T, rate=rate)

works for me.

Answered By - Sam Mason