#mp3

Working with audio files in Python, advanced use cases (24-bit, 32-bit, cue and loop markers, etc.)

Python comes with the built-in wave module and for most use cases, it's enough to read and write .wav audio files.

But in some cases, you need to be able to work with 24 or 32-bit audio files, to read cue markers, loop markers or other metadata (required for example when designing a sampler software). As I needed this for various projects such as SamplerBox, here are some contributions I made:

1. The Python standard library's wave module doesn't read cue markers and doesn't support 24-bit files. Here is an updated module:

   wave.py (enhanced)

   that adds some little useful things. (See Revision #1 to see diff with the original stdlib code).

   Usage example:

   from wave import open
   f = open('Take1.wav')
   print(f.getmarkers())

   If you're familiar with main Python repositery contributions (I'm not), feel free to include these additions there.

2. The module scipy.io.wavfile is very useful too. So here is an enhanced version:

   wavfile.py (enhanced)

   Among other things, it adds 24-bit and 32-bit IEEE support, cue marker & cue marker labels support, pitch metadata, etc.

   Usage example:

   from wavfile import read, write
   sr, samples, br, cue, cuelabels, cuelist, loops, f0 = read('Take1.wav', readmarkers=True, 
       readmarkerlabels=True, readmarkerslist=True, readpitch=True, readloops=True)
   write('Take2.wav', sr, samples, bitrate=br, markers=cue, loops=loops, pitch=130.82)

   Here is a Github post and pull-request about a hypothetical merge to Scipy.

Here is how loop markers look like in the good old (non open-source but soooo useful) SoundForge:

Lastly, this is how to convert a WAV to MP3 with pydub, for future reference. As usual, do pip install pydub and make sure ffmpeg is in the system path. Then:

from pydub import AudioSegment
song = AudioSegment.from_wav("test.wav")
song.export("test.mp3", format="mp3", bitrate="256k")

will convert a WAV file to MP3.

Interested for future evolutions and other audio programming tools?