NORMALIZE-AUDIO(1)														NORMALIZE-AUDIO(1)

NAME

       normalize-audio - adjusts volume levels of audio files.

SYNOPSIS

       normalize-audio [ options ] [ -- ] file ...

DESCRIPTION

       normalize-audio	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-audio operates in 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 to set each file'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 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 decibels.  By default, volume adjustments are shown in  decibels,  and  volume
	      levels in 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 your MP3 player does not recognize ID3v2.4 tags.	See MPEG AUDIO ADJUSTMENT,
	      below, for details.

       --id3-unsync
	      Use this option when adjusting MPEG audio files if 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 samples above -6dBFS (0.5) are limited, but this option sets the limit-
	      ing 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 the volume 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 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 will be adjusted so that its maximum sample is at full scale.	This  just
	      gives a file the maximum volume possible without clipping; no normalization is done.

       -q, --quiet
	      Don't output progress information.  Only error 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 aver-
	      age.  A high value here (say, 50) will make sure that the volumes of all files are considered in the average.

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

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

       -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 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 mat-
       ter if 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  com-
       puted, and each file 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 aver-
       aging the volumes of all the files, computing a single adjustment from that, and applying the same adjustment to all the files.	Some anal-
       ysis  is  also done so that files with volumes that appear to be statistical aberrations are not considered in the average.  This is useful
       if you have albums (like many of the author's) in 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 their ID3 tags.  There is a frame for this, called  "RVA2",  that
       does exactly what we want, and is a native frame in ID3v2.4.  Unfortunately, many MP3 players do not support v2.4 tags, and the RVA2 tag is
       not native in 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 2.4, and use RVA2 tags.  This is the default behavior, in the hope that eventually MP3 players
	  will support v2.4 tags and this won't be a problem anymore.

       2. Upgrade the tag to only version 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 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 your MP3 player knows about ID3v2 tags, you don't need it.

CAVEATS

       Note that your version of normalize-audio must be compiled with MAD library support to analyze MP3 file volume levels.

AUTHOR

       Chris Vaill <chrisvaill@gmail.com>

SEE ALSO

       sox(1)

								 14 September 2005						NORMALIZE-AUDIO(1)