Volume normalization

[mats_a]

Below is some volume-normalization code I wrote, since mplayer's -volnorm can cause distortion. The idea is to ask mplayer to return the average dB volume of the song and subtract that off from a base. Downside: sound daemon volume will need to be set a bit higher. I'll try to port it to Perl when I get around to adding argument support to gbr, but if someone else wants to handle this please go ahead.

#!/usr/bin/python

"""
author: Mats Ahlgren
licensed under whatever Gutenbach wants

% ./get-loudness.sh MUSICFILE.mp3
{'max_volume': ' -1 dB', 'histogram_3db': ' 10607', 'mean_volume': ' -19 dB', 'n_samples': ' 43497216', 'histogram_4db': ' 29967', 'histogram_5db': ' 53578', 'histogram_1db': ' 1', 'histogram_2db': ' 725'}

let $v = 20-mean_volume  <-- necessary because boosting volume above 0 can cause distortion
then do: mplayer -af volume=$v MUSICFILE.mp3
"""

from subprocess import *
import sys

args = sys.argv[1:]
assert len(args)==1

arg = args[0]
command = "mplayer -quiet -ao pcm:fast:file=/dev/null -af stats".split() + [arg]
output = Popen(command, stdout=PIPE, stderr=PIPE).communicate()[0]

stats = dict(line[7:].split(':') for line in output.split('\n') if ('stat' in line))

print stats