NAME

       mp3gain — lossless mp3 normalizer

SYNOPSIS

       mp3gain [options]  [infile]  [infile 2 ...]

DESCRIPTION

       This manual page documents briefly the mp3gain       command.

       This  manual  page  was written for the Debian distribution because the
       original program does not have a manual page.

       mp3gain can analyze and adjust mp3 files so that  they  have  the  same
       volume.

       mp3gain  does  not  just do peak normalization, as many normalizers do.
       Instead, it does some statistical analysis to determine  how  loud  the
       file  actually sounds to the human ear. Also, the changes mp3gain makes
       are completely lossless. There is no quality lost in the change because
       the  program  adjusts  the  mp3 file directly, without decoding and re-
       encoding. Also, this works with all mp3 players, i.e. no support for  a
       special tag or something similar is required.

       mp3gain  actually changes your file’s gain only when you use one of the
       options -r,  -a, -g, or -l. If none of these options is given,  only  a
       tag denoting the recommended gain change is written to the file. If you
       only want to print the recommended gain change (and not modify the file
       at all) you have to use the -s s (skip tag) option.

       The method mp3gain uses to determine the desired volume is described at
       www.replaygain.org (link to URL http://www.replaygain.org/) .  See also
       /usr/share/doc/README.method .

OPTIONS

       -?           -h
                 Show summary of options.

       -g i      apply gain i to mp3 without doing any analysis

       -l 0 i    apply gain i to channel 0 (left channel) of mp3 without doing
                 any analysis (ONLY works for STEREO mp3s,  not  Joint  Stereo
                 mp3s)

       -l 1 i    apply  gain  i  to  channel  1 (right channel) of mp3 without
                 doing any analysis (ONLY works for  STEREO  mp3s,  not  Joint
                 Stereo mp3s)

       -r        apply  Track  gain  automatically  (all  files  set  to equal
                 loudness)

       -k        automatically lower Track gain to not clip audio

       -a        apply Album gain automatically (files are all from  the  same
                 album: a single gain change is applied to all files, so their
                 loudness relative to each other remains  unchanged,  but  the
                 average album loudness is normalized)

       -m i      modify suggested MP3 gain by integer i

       -d n      modify suggested dB gain by floating-point n

       -c        ignore clipping warning when applying gain

       -o        output is a database-friendly tab-delimited list

       -t        mp3gain  writes  modified  mp3  to  temp  file,  then deletes
                 original instead of modifying bytes in original file (This is
                 the default in Debian)

       -T        mp3gain  modifys bytes in original file instead of writing to
                 temp file.

       -q        Quiet mode: no status messages

       -p        Preserve original file timestamp

       -x        Only find max. amplitude of mp3

       -f        Force mp3gain to assume input file is an  MPEG  2  Layer  III
                 file  (i.e.  don’t  check  for  mis-named Layer I or Layer II
                 files)

       -s c      only check stored tag info (no other processing)

       -s d      delete stored tag info (no other processing)

       -s s      skip (ignore) stored tag info (do not read or write tags)

       -s r      force re-calculation (do not read tag info)

       -u        undo changes made by mp3gain (based on stored tag info)

       -w        "wrap" gain change if gain+change > 255 or  gain+change  <  0
                 (see below or use -? wrap switch for a complete explanation)

       -v        Show version of program.

       If you specify -r and -a, only the second one will work.

       If you do not specify -c, the program will stop and ask before applying
       gain change to a file that might clip

   The WRAP option
       Here’s the problem: The "global gain" field that mp3gain adjusts is  an
       8-bit unsigned integer, so the possible values are 0 to 255.

       MOST  mp3 files (in fact, ALL the mp3 files I’ve examined so far) don’t
       go over 230. So there’s plenty of headroom on top--  you  can  increase
       the gain by 37dB (multiplying the amplitude by 76) without a problem.

       The  problem is at the bottom of the range. Some encoders create frames
       with 0 as the global gain for silent frames.   What  happens  when  you
       _lower_ the global gain by 1?  Well, in the past, mp3gain always simply
       wrapped the result up to 255.  That way, if you lowered the gain by any
       amount  and  then raised it by the same amount, the mp3 would always be
       _exactly_ the same.

       There are a few encoders out there, unfortunately, that  create  0-gain
       frames  with other audio data in the frame.  As long as the global gain
       is 0, you’ll never hear the data.  But if you lower the gain on such  a
       file,  the  global  gain is suddenly _huge_.  If you play this modified
       file, there might be a brief, very loud blip.

       So now the default behavior of mp3gain is to _not_ wrap  gain  changes.
       In other words,

          1. If the gain change would make a frame’s global gain drop below 0,
             then the global gain is set to 0.

          2. If the gain change would make a frame’s global  gain  grow  above
             255, then the global gain is set to 255.

          3.   If a frame’s global gain field is already 0, it is not changed,
             even if the gain change is a positive number.

       To use the original "wrapping" behavior, use the -w switch.

SEE ALSO

       The homepage of mp3gain is located  at  http://mp3gain.sourceforge.net/
       (link to URL http://mp3gain.sourceforge.net/)  .

AUTHOR

       This  manual  page was written by Stefan Fritsch sf@sfritsch.de for the
       Debian system (but may be used by others).  Permission  is  granted  to
       copy, distribute and/or modify this document under the terms of the GNU
       Lesser General  Public  License,  Version  2.1  or  any  later  version
       published by the Free Software Foundation.

       On  Debian  systems, the complete text of the GNU Lesser General Public
       License can be found in /usr/share/common-licenses/LGPL.

                                                                    MP3GAIN(1)