Ubuntu Manpage: normalize-audio - adjusts volume levels of WAV or MP3 audio files.

Provided by: normalize-audio_0.7.7-15_amd64

NAME

       normalize-audio - adjusts volume levels of WAV or MP3 audio files.

SYNOPSIS

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

DESCRIPTION

       normalize-audio  is  used  to  adjust  the  volume of WAV or MP3 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 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 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 average. 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 matter 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 computed, 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 averaging 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 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>