how to save a wav file that plays two tracks at the same time? at different volumes

Question

I'm coding in python and using the "wave" library. I've managed to save new wave files with this library, but not with two sound files overlapping - they will be played one after another when saved. if anyone could help with how to save a file where two tracks play at the same time at different volumes would be great. thanks.

Possible duplicate of [Mixing two audio files together with python](http://stackoverflow.com/questions/4039158/mixing-two-audio-files-together-with-python) — litepresence, Apr 01 '17 at 18:50

score 2 · Accepted Answer · answered Apr 02 '17 at 13:08

You can use the pydub library (a light wrapper I wrote around the python wave module in the std lib) to do it pretty simply:

from pydub import AudioSegment

sound1 = AudioSegment.from_file("/path/to/my_sound.wav")
sound2 = AudioSegment.from_file("/path/to/another_sound.wav")

combined = sound1.overlay(sound2)

combined.export("/path/to/combined.wav", format='wav')

but if you really want to do it using wave:

this is very dependent of the format these are in. Here's an example of how to do it assuming 2 byte wide, little-endian samples:

import wave

w1 = wave.open("/path/to/wav/1")
w2 = wave.open("/path/to/wav/2")

#get samples formatted as a string.
samples1 = w1.readframes(w1.getnframes())
samples2 = w2.readframes(w2.getnframes())

#takes every 2 bytes and groups them together as 1 sample. ("123456" -> ["12", "34", "56"])
samples1 = [samples1[i:i+2] for i in xrange(0, len(samples1), 2)]
samples2 = [samples2[i:i+2] for i in xrange(0, len(samples2), 2)]

#convert samples from strings to ints
def bin_to_int(bin):
    as_int = 0
    for char in bin[::-1]: #iterate over each char in reverse (because little-endian)
        #get the integer value of char and assign to the lowest byte of as_int, shifting the rest up
        as_int <<= 8
        as_int += ord(char) 
    return as_int

samples1 = [bin_to_int(s) for s in samples1] #['\x04\x08'] -> [0x0804]
samples2 = [bin_to_int(s) for s in samples2]

#average the samples:
samples_avg = [(s1+s2)/2 for (s1, s2) in zip(samples1, samples2)]

And now all that's left to do is convert samples_avg back to a binary string and write that to a file using wave.writeframes. That's just the inverse of what we just did, so it shouldn't be too hard to figure out. For your int_to_bin function, you'll probably what to make use of the function chr(code), which returns the character with the character code of code (opposite of ord)

thanks for all the help- pydub is what i need. but when i tried to import AudioSegment in python it doesn't recognize it. (i pip installed pydub and tried doing the same for AudioSegment). How can i fix that problem? — Sh0z, Apr 02 '17 at 14:16
wanted to add that i tried searching online and also found nothing — Sh0z, Apr 02 '17 at 14:25

how to save a wav file that plays two tracks at the same time? at different volumes

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