1MP3GAIN(1) General Commands Manual MP3GAIN(1)
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6 mp3gain — lossless mp3 normalizer
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9 mp3gain [options] [infile] [infile 2 ...]
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12 This manual page documents briefly the mp3gain command.
13 This manual page was written for the Debian distribution because the
15 original program does not have a manual page.
16 mp3gain can analyze and adjust mp3 files so that they have the same
19 volume.
20 mp3gain does not just do peak normalization, as many normalizers do.
22 Instead, it does some statistical analysis to determine how loud the
23 file actually sounds to the human ear. Also, the changes mp3gain makes
24 are completely lossless. There is no quality lost in the change because
25 the program adjusts the mp3 file directly, without decoding and re-
26 encoding. Also, this works with all mp3 players, i.e. no support for a
27 special tag or something similar is required.
28 mp3gain actually changes your file's gain only when you use one of the
30 options -r, -a, -g, or -l. If none of these options is given, only a
31 tag denoting the recommended gain change is written to the file. If you
32 only want to print the recommended gain change (and not modify the file
33 at all) you have to use the -s s (skip tag) option.
34 The method mp3gain uses to determine the desired volume is described at
36 www.replaygain.org (link to URL http://www.replaygain.org/) . See also
37 /usr/share/doc/mp3gain-1.4.6/README.method .
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40 -? -h
41 Show summary of options.
42 -g i apply gain i to mp3 without doing any analysis
44 -l 0 i apply gain i to channel 0 (left channel) of mp3 without doing
46 any analysis (ONLY works for STEREO mp3s, not Joint Stereo
47 mp3s)
48 -l 1 i apply gain i to channel 1 (right channel) of mp3 without
50 doing any analysis (ONLY works for STEREO mp3s, not Joint
51 Stereo mp3s)
52 -r apply Track gain automatically (all files set to equal loud‐
54 ness)
55 -k automatically lower Track gain to not clip audio
57 -a apply Album gain automatically (files are all from the same
59 album: a single gain change is applied to all files, so their
60 loudness relative to each other remains unchanged, but the
61 average album loudness is normalized)
62 -m i modify suggested MP3 gain by integer i
64 -d n modify suggested dB gain by floating-point n
66 -c ignore clipping warning when applying gain
68 -o output is a database-friendly tab-delimited list
70 -t mp3gain writes modified mp3 to temp file, then deletes origi‐
72 nal instead of modifying bytes in original file (This is the
73 default in Debian)
74 -T mp3gain modifys bytes in original file instead of writing to
76 temp file.
77 -q Quiet mode: no status messages
79 -p Preserve original file timestamp
81 -x Only find max. amplitude of mp3
83 -f Force mp3gain to assume input file is an MPEG 2 Layer III
85 file (i.e. don't check for mis-named Layer I or Layer II
86 files)
87 -s c only check stored tag info (no other processing)
89 -s d delete stored tag info (no other processing)
91 -s s skip (ignore) stored tag info (do not read or write tags)
93 -s r force re-calculation (do not read tag info)
95 -u undo changes made by mp3gain (based on stored tag info)
97 -w "wrap" gain change if gain+change > 255 or gain+change < 0
99 (see below or use -? wrap switch for a complete explanation)
100 -v Show version of program.
102 If you specify -r and -a, only the second one will work.
104 If you do not specify -c, the program will stop and ask before applying
106 gain change to a file that might clip
107 The WRAP option
109 Here's the problem: The "global gain" field that mp3gain adjusts is an
110 8-bit unsigned integer, so the possible values are 0 to 255.
111 MOST mp3 files (in fact, ALL the mp3 files I've examined so far) don't
114 go over 230. So there's plenty of headroom on top-- you can increase
115 the gain by 37dB (multiplying the amplitude by 76) without a problem.
116 The problem is at the bottom of the range. Some encoders create frames
119 with 0 as the global gain for silent frames. What happens when you
120 _lower_ the global gain by 1? Well, in the past, mp3gain always simply
121 wrapped the result up to 255. That way, if you lowered the gain by any
122 amount and then raised it by the same amount, the mp3 would always be
123 _exactly_ the same.
124 There are a few encoders out there, unfortunately, that create 0-gain
127 frames with other audio data in the frame. As long as the global gain
128 is 0, you'll never hear the data. But if you lower the gain on such a
129 file, the global gain is suddenly _huge_. If you play this modified
130 file, there might be a brief, very loud blip.
131 So now the default behavior of mp3gain is to _not_ wrap gain changes.
134 In other words,
135 1. If the gain change would make a frame's global gain drop below 0,
138 then the global gain is set to 0.
139 2. If the gain change would make a frame's global gain grow above
142 255, then the global gain is set to 255.
143 3.
146 If a frame's global gain field is already 0, it is not changed,
148 even if the gain change is a positive number.
149 To use the original "wrapping" behavior, use the -w switch.
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155 The homepage of mp3gain is located at http://mp3gain.sourceforge.net/
156 (link to URL http://mp3gain.sourceforge.net/) .
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160 This manual page was written by Stefan Fritsch sf@sfritsch.de for the
161 Debian system (but may be used by others). Permission is granted to
162 copy, distribute and/or modify this document under the terms of the GNU
163 Lesser General Public License, Version 2.1 or any later version pub‐
164 lished by the Free Software Foundation.
165 MP3GAIN(1)