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normalize(1) - normalize - adjusts volume levels of audio files - man 1 normalize

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NORMALIZE(1)                                                      NORMALIZE(1)



NAME
       normalize - adjusts volume levels of audio files.

SYNOPSIS
       normalize [ options ]  [ -- ]  file...

DESCRIPTION
       normalize is used to adjust the volume of wav audio files to a standard
       volume level. This is useful for things like creating mp3 mixes,  where
       different  recording levels on different albums can cause the volume to
       vary greatly from song to song.

       normalize operates in(1,8) two phases. In the first phase, it  analyzes  the
       specified  files  as  wav  audio files, and computes the volume of each
       file. In the second phase, it applies a volume adjustment to each  file(1,n)
       to set(7,n,1 builtins) each file(1,n)'s volume to a standard level.

OPTIONS
       -a, --amplitude=AMPLITUDE
              Adjust the RMS volume to the target amplitude AMPLITUDE; must be
              between 0.0 and 1.0. If a number suffixed by "dB" or  "dBFS"  is
              specified,  the amplitude is assumed to be in(1,8) decibels from full
              scale.  The default is -12dBFS.

       -b, --batch
              Enable batch mode: see BATCH MODE, below.

       -c, --compression
              Deprecated. In previous versions, this enabled the limiter,  but
              now the limiter is enabled by default.

       --clipping
              Disable  the  limiter,  and  just  clip any samples that are too
              large.  Same effect as -l 0dBFS.

       --fractions
              Display all values as decimal fractions instead of in(1,8)  decibels.
              By default, volume adjustments are shown in(1,8) decibels, and volume
              levels in(1,8) dBFS, where 0 dBFS is the level of a  square  wave  of
              maximum amplitude.

       -g, --gain=GAIN
              Skip  the  volume  computation  phase:  don't compute the volume
              adjustment from the current volumes of the files. Instead,  just
              apply  the  given gain as a volume adjustment to all files. As a
              plain number this is just a multiplier applied to  all  samples,
              If  a  number  suffixed  by  "dB"  is specified, all volumes are
              adjusted by that many decibels.

       --id3-compat
              Use this option when adjusting MPEG  audio  files  if(3,n)  your  MP3
              player  does  not recognize ID3v2.4 tags. See MPEG AUDIO ADJUST-
              MENT, below, for details.

       --id3-unsync
              Use this option when adjusting MPEG  audio  files  if(3,n)  your  MP3
              player  does  not  recognize  ID3v2 tags and has trouble playing
              some ID3v2 tagged MP3 files. See MPEG AUDIO  ADJUSTMENT,  below,
              for details.

       -l, --limiter=LEVEL
              This  controls the behavior of the limiter. By default, all sam-
              ples above -6dBFS (0.5) are limited, but this  option  sets  the
              limiting  level  to LEVEL. Setting LEVEL to 1 (or 0dBFS) does no
              limiting (clipping is done instead); setting  LEVEL  to  0  does
              limiting on all samples. The default value is recommended unless
              you know what you're doing.

       -m, --mix
              Enable mix mode: see MIX MODE, below.  Batch mode and  mix  mode
              are mutually exclusive.

       -n, --no-adjust
              Compute and output the volume adjustment that would set(7,n,1 builtins) the vol-
              ume to the target, but don't apply it to any of the files  (i.e.
              skip  the second phase). If you use this option, your files will
              not be altered in(1,8) any way.

       --no-progress
              Don't print any progress information.  All  other  messages  are
              printed as normal according to the verbosity level.

       --peak Adjust  using  peak levels instead of RMS levels. Each file(1,n) will
              be adjusted so that its maximum sample is at  full  scale.  This
              just  gives a file(1,n) the maximum volume possible without clipping;
              no normalization is done.

       -q, --quiet
              Don't output  progress  information.  Only  error(8,n)  messages  are
              printed.

       -t, --average-threshold=THRESHOLD
              When  averaging  volume levels for batch mode or mix mode, throw
              out any volumes that are more than THRESHOLD decibels  from  the
              average.  A  high  value  here (say, 50) will make sure that the
              volumes of all files are considered in(1,8) the average.

       -T, --adjust-threshold=THRESHOLD
              If an adjustment to be made to a file(1,n) is smaller than  THRESHOLD
              decibels,  consider the file(1,n) already normalized and don't do the
              adjustment. This is 0.125 by default, or 0 if(3,n) the -g  option  is
              given.

       -v, --verbose
              Increase  verbosity.  This  option can be repeated for more mes-
              sages.

       -w, --output-bitwidth
              Force output files to have samples that are W  bits  wide.  This
              option is ignored when adjusting MP3 files.

       -h, --help
              Display usage information and exit.

       -V, --version
              Print version(1,3,5) information and exit.

       --     Terminate option list.

MIX MODE
       This  mode  is  made especially for making mixed CD's and the like. You
       want every song on the mix to be the same volume, but it doesn't matter
       if(3,n)  they  are  the  same volume as the songs on some other mix you made
       last week. In mix mode, average level of all the files is computed, and
       each file(1,n) is separately normalized to this average volume.

BATCH MODE
       When  operating  on a group of unrelated files, you usually want all of
       them at the same level, and this is the default  behavior.  However,  a
       group  of  music files all from the same album is generally meant to be
       listened to at the relative volumes they were  recorded  at.  In  batch
       mode,  all  the  specified  files are considered to be part of a single
       album and their relative volumes are preserved. This is done by averag-
       ing  the  volumes  of all the files, computing a single adjustment from
       that, and applying the same adjustment to all the files. Some  analysis
       is  also  done so that files with volumes that appear to be statistical
       aberrations are not considered in(1,8) the average. This is  useful  if(3,n)  you
       have  albums  (like  many of the author's) in(1,8) which there is one "quiet
       song" that throws off the average.

MPEG AUDIO ADJUSTMENT
       MP3 files are "adjusted" by setting a relative volume adjustment  frame
       in(1,8)  their ID3 tags. There is a frame for this, called "RVA2", that does
       exactly what we want, and is a native frame in(1,8) ID3v2.4.  Unfortunately,
       many  MP3  players do not support v2.4 tags (including xmms, as of this
       writing), and the RVA2 tag is not native in(1,8) previous ID3  versions.  In
       fact,  adding  an  RVA2  frame to a v2.3 tag confuses some MP3 players.
       Therefore, we are left with two  choices  when  trying  to  add  volume
       adjustment information to an ID3 tag:

       1.     Go  ahead and upgrade the tag to version(1,3,5) 2.4, and use RVA2 tags.
              This is the default behavior, in(1,8) the hope  that  eventually  MP3
              players  will support v2.4 tags and this won't be a problem any-
              more.

       2.     Upgrade the tag to only version(1,3,5) 2.3. Instead  of  RVA2,  use  an
              "XRVA"  tag  with  the  same format as an RVA2 tag. This isn't a
              native frame, but since it starts with an "X",  it's  considered
              experimental and therefore legal, according to the ID3 spec. The
              --id3-compat option turns on this behavior.

       The disadvantage of the first method is that your  MP3  player  may  no
       longer read(2,n,1 builtins) the ID3 tags on your files. Bug the author of your favorite
       MP3 player to support ID3v2.4 tags!

       The disadvantage of the second method is that the XRVA  frame  is  only
       recognized  by  the xmms-rva plugin that is packaged with normalize. On
       the other hand, I don't know of any MP3 players that recognize the RVA2
       frame, either, so it may not make any difference.

       The  other  option related to ID3 tags, --id3-unsync, is only necessary
       for compatibility with old MP3 players that don't recognize ID3v2  tags
       at  all. If your MP3 player complains of garbage at the start of tagged
       files, or is unable to play the files at  all,  turn  this  option  on.
       This option should never hurt, but if(3,n) your MP3 player knows about ID3v2
       tags, you don't need it.

CAVEATS
       Note that your version(1,3,5) of normalize must be compiled with  MAD  library
       support to analyze MP3 file(1,n) volume levels.

AUTHOR
       Chris Vaill <cvaill@cs.columbia.edu>

SEE ALSO
       sox(1)



                                  2001-09-16                      NORMALIZE(1)

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