how to convert wav file to float amplitude

Question

so I asked everything in the title:

I have a wav file (written by PyAudio from an input audio) and I want to convert it in float data corresponding of the sound level (amplitude) to do some fourier transformation etc...

Anyone have an idea to convert WAV data to float?

Answer 1

I have identified two decent ways of doing this.

Method 1: using the wavefile module

Use this method if you don't mind installing some extra libraries which involved a bit of messing around on my Mac but which was easy on my Ubuntu server.

https://github.com/vokimon/python-wavefile

import wavefile

# returns the contents of the wav file as a double precision float array
def wav_to_floats(filename = 'file1.wav'):
    w = wavefile.load(filename)
    return w[1][0]

signal = wav_to_floats(sys.argv[1])
print "read "+str(len(signal))+" frames"
print  "in the range "+str(min(signal))+" to "+str(min(signal))

Method 2: using the wave module

Use this method if you want less module install hassles.

Reads a wav file from the filesystem and converts it into floats in the range -1 to 1. It works with 16 bit files and if they are > 1 channel, will interleave the samples in the same way they are found in the file. For other bit depths, change the 'h' in the argument to struct.unpack according to the table at the bottom of this page:

https://docs.python.org/2/library/struct.html

It will not work for 24 bit files as there is no data type that is 24 bit, so there is no way to tell struct.unpack what to do.

import wave
import struct
import sys

def wav_to_floats(wave_file):
    w = wave.open(wave_file)
    astr = w.readframes(w.getnframes())
    # convert binary chunks to short 
    a = struct.unpack("%ih" % (w.getnframes()* w.getnchannels()), astr)
    a = [float(val) / pow(2, 15) for val in a]
    return a

# read the wav file specified as first command line arg
signal = wav_to_floats(sys.argv[1])
print "read "+str(len(signal))+" frames"
print  "in the range "+str(min(signal))+" to "+str(min(signal))