#!/usr/bin/perl

unless (@ARGV) {
    die "usage: $0 mp3file [ mp3file ... ]\n";
}

@quotedfiles = map { qq("$_") } @ARGV;

$listout = `mp3gain -o @quotedfiles`;

($albumgain) = ($listout =~ /^"Album"\s+(\S+)/m);

print "Will attempt to apply MP3 gain of $albumgain\n";

for $file (@quotedfiles) {
    $stdout = `mp3gain -g $albumgain $file`;  
}

However, the problem is that if the recommended album gain clips, it won't be detected by mp3gain -g. I can't seem to find a switch that will test to see if a gain clips before applying. If one exists, the gain could back down until the highest non-clipping gain is found.

Could we just use the /k switch at the same time?  Would this effectively override the value specified by /g  - or maybe even be processed following the /g value is applied?

Or, would the value obtained from /o take this into consideration anyway?  Perhaps it strives for 89dB, but will go lower if required.

#!/usr/bin/perl

unless (@ARGV) {
    die "usage: $0 mp3file [ mp3file ... ]\n";
}

$clipped = 0;

@quotedfiles = map { qq("$_") } @ARGV;

$listout = `mp3gain -o @quotedfiles`;

($albumgain) = ($listout =~ /^"Album"\s+(\S+)/m);
@maxsample = ($listout =~ /^.+?\t-*\d+\s+\S+\s+(\d+\.\d+)/mg);

print "Will attempt to apply MP3 gain of $albumgain\n";

if ($albumgain > 0) {
    for (0 .. $#maxsample) {
        while ($maxsample[$_] * (2**($albumgain/4)) > 32767) {
            $clipped = 1;
            $albumgain--;
        }
    }
}

if ($clipped) {
    print "Clipping detected - reducing MP3 gain to $albumgain\n";
}

if ($albumgain != 0) {
    for $file (@quotedfiles) {
        $stdout = `mp3gain -g $albumgain $file`;
    }
} else {
    print "No processing required for MP3 gain 0\n";
}

• Run -a -k to apply max no-clip value
• Run -o to get Album gain
• If gain is still negative value run -g

I'm on OS X and would also like to know the command line options (especially increasing to 92 over default 89). Haven't found anything on the web more than generic "-r -p -t -k", etc. Any help or links would be greatly appreciated.

If I wanted to set volume to 92 dB, I'd try altering the volume to 89 dB first, then running /g 2. (A 3-dB difference means two steps.)

Question in general about mp3gain. If i run this script against several directories of mp3s at once, each dir a single album, will it compute the album gain for each individual album or for the entire set of files?

# -*- coding: utf-8 -*-          
#/usr/bin/python                 

import sys
import os 
import subprocess

def dirEntries(dir_name, subdir, *args):
    fileList = []                       
    for file in os.listdir(dir_name):
        dirfile = os.path.join(dir_name, file)
        if os.path.isfile(dirfile):
            if not args:
                fileList.append(dirfile)
            else:
                if os.path.splitext(dirfile)[1][1:] in args:
                    fileList.append(dirfile)
        # recursively access file names in subdirectories
        elif os.path.isdir(dirfile) and subdir:
            fileList.extend(dirEntries(dirfile, subdir, *args))
    return fileList

def dirNamesWithFiles(dir_name, subdir, *args):
    folderList = []
    for file in os.listdir(dir_name):
        dirfile = os.path.join(dir_name, file)
        if os.path.isfile(dirfile):
            if not args:
                folderList.append(os.path.dirname(dirfile))
            else:
                if os.path.splitext(dirfile)[1][1:] in args:
                    folderList.append(os.path.dirname(dirfile))
        # recursively access file names in subdirectories
        elif os.path.isdir(dirfile) and subdir:
            folderList.extend(dirNamesWithFiles(dirfile, subdir, *args))
    return folderList

perlPath='/home/n/applyMp3Gain.pl'
mp3Path='/home/n/Mp3-Files'

folders = set(dirNamesWithFiles(mp3Path, 1, 'mp3'))
for i in folders:
        subprocess.call(["/usr/bin/perl", perlPath] + dirEntries(i, 0, 'mp3'))

If I wanted to set volume to 92 dB, I'd try altering the volume to 89 dB first, then running /g 2. (A 3-dB difference means two steps.)