Provided by: mp3gain_1.5.2-r2-6_amd64 bug


       mp3gain — lossless mp3 normalizer


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


       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-

       mp3gain optionally writes gain adjustments directly into the encoded data. In  this  case,
       the  adjustment works with all mp3 players, i.e. no support for a special tag is required.
       This mode is activated by any of the options -r, -a, -g, or -l.

       If none of the above options are given, the recommended gain change is instead written  to
       a  special  tag  in the mp3 file. In this case, the adjustment only works with mp3 players
       that support this tag.  Some mp3 players refer to this as ReplayGain.  The tag is  written
       either  in  APEv2  format  (default)  or in ID3v2 format (with -s i).  If you only want to
       print the recommended gain change (and not modify the file at all) you may use  the  -s  s
       (skip tag) option.

       The method mp3gain uses to determine the desired volume is described at
       (link to URL .  See also  /usr/share/doc/mp3gain/README.method


       -?           -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 modifies 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 i      use  ID3v2  tag  for  gain information; if the file contained gain data in APEv2
                 format, it is upgraded to ID3v2

       -s a      use APEv2 tag for gain information (default)

       -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.


             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.


       The  homepage  of  mp3gain  is  located  at  (link to URL  .


       This manual page was written by Stefan Fritsch 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.