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

Provided by: normalize-audio_0.7.7-18_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>