1NORMALIZE(1) NORMALIZE(1)
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6 normalize - adjusts volume levels of audio files.
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9 normalize [ options ] [ -- ] file ...
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13 normalize is used to adjust the volume of wav audio files to a standard
14 volume level. This is useful for things like creating mp3 mixes, where
15 different recording levels on different albums can cause the volume to
16 vary greatly from song to song.
17 normalize operates in two phases. In the first phase, it analyzes the
19 specified files as wav audio files, and computes the volume of each
20 file. In the second phase, it applies a volume adjustment to each file
21 to set each file's volume to a standard level.
22
24 -a, --amplitude=AMPLITUDE
25 Adjust the RMS volume to the target amplitude AMPLITUDE; must be
26 between 0.0 and 1.0. If a number suffixed by "dB" or "dBFS" is
27 specified, the amplitude is assumed to be in decibels from full
28 scale. The default is -12dBFS.
29 -b, --batch
31 Enable batch mode: see BATCH MODE, below.
32 -c, --compression
34 Deprecated. In previous versions, this enabled the limiter, but
35 now the limiter is enabled by default.
36 --clipping
38 Disable the limiter, and just clip any samples that are too
39 large. Same effect as -l 0dBFS.
40 --fractions
42 Display all values as decimal fractions instead of in decibels.
43 By default, volume adjustments are shown in decibels, and volume
44 levels in dBFS, where 0 dBFS is the level of a square wave of
45 maximum amplitude.
46 -g, --gain=GAIN
48 Skip the volume computation phase: don't compute the volume ad‐
49 justment from the current volumes of the files. Instead, just
50 apply the given gain as a volume adjustment to all files. As a
51 plain number this is just a multiplier applied to all samples,
52 If a number suffixed by "dB" is specified, all volumes are ad‐
53 justed by that many decibels.
54 --id3-compat
56 Use this option when adjusting MPEG audio files if your MP3
57 player does not recognize ID3v2.4 tags. See MPEG AUDIO ADJUST‐
58 MENT, below, for details.
59 --id3-unsync
61 Use this option when adjusting MPEG audio files if your MP3
62 player does not recognize ID3v2 tags and has trouble playing
63 some ID3v2 tagged MP3 files. See MPEG AUDIO ADJUSTMENT, below,
64 for details.
65 -l, --limiter=LEVEL
67 This controls the behavior of the limiter. By default, all sam‐
68 ples above -6dBFS (0.5) are limited, but this option sets the
69 limiting level to LEVEL. Setting LEVEL to 1 (or 0dBFS) does no
70 limiting (clipping is done instead); setting LEVEL to 0 does
71 limiting on all samples. The default value is recommended un‐
72 less you know what you're doing.
73 -m, --mix
75 Enable mix mode: see MIX MODE, below. Batch mode and mix mode
76 are mutually exclusive.
77 -n, --no-adjust
79 Compute and output the volume adjustment that would set the vol‐
80 ume to the target, but don't apply it to any of the files (i.e.
81 skip the second phase). If you use this option, your files will
82 not be altered in any way.
83 --no-progress
85 Don't print any progress information. All other messages are
86 printed as normal according to the verbosity level.
87 --peak Adjust using peak levels instead of RMS levels. Each file will
89 be adjusted so that its maximum sample is at full scale. This
90 just gives a file the maximum volume possible without clipping;
91 no normalization is done.
92 -q, --quiet
94 Don't output progress information. Only error messages are
95 printed.
96 -t, --average-threshold=THRESHOLD
98 When averaging volume levels for batch mode or mix mode, throw
99 out any volumes that are more than THRESHOLD decibels from the
100 average. A high value here (say, 50) will make sure that the
101 volumes of all files are considered in the average.
102 -T, --adjust-threshold=THRESHOLD
104 If an adjustment to be made to a file is smaller than THRESHOLD
105 decibels, consider the file already normalized and don't do the
106 adjustment. This is 0.125 by default, or 0 if the -g option is
107 given.
108 -v, --verbose
110 Increase verbosity. This option can be repeated for more mes‐
111 sages.
112 -w, --output-bitwidth
114 Force output files to have samples that are W bits wide. This
115 option is ignored when adjusting MP3 files.
116 -h, --help
118 Display usage information and exit.
119 -V, --version
121 Print version information and exit.
122 -- Terminate option list.
124
126 This mode is made especially for making mixed CD's and the like. You
127 want every song on the mix to be the same volume, but it doesn't matter
128 if they are the same volume as the songs on some other mix you made
129 last week. In mix mode, average level of all the files is computed,
130 and each file is separately normalized to this average volume.
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133 When operating on a group of unrelated files, you usually want all of
134 them at the same level, and this is the default behavior. However, a
135 group of music files all from the same album is generally meant to be
136 listened to at the relative volumes they were recorded at. In batch
137 mode, all the specified files are considered to be part of a single al‐
138 bum and their relative volumes are preserved. This is done by averag‐
139 ing the volumes of all the files, computing a single adjustment from
140 that, and applying the same adjustment to all the files. Some analysis
141 is also done so that files with volumes that appear to be statistical
142 aberrations are not considered in the average. This is useful if you
143 have albums (like many of the author's) in which there is one "quiet
144 song" that throws off the average.
145
147 MP3 files are "adjusted" by setting a relative volume adjustment frame
148 in their ID3 tags. There is a frame for this, called "RVA2", that does
149 exactly what we want, and is a native frame in ID3v2.4. Unfortunately,
150 many MP3 players do not support v2.4 tags, and the RVA2 tag is not na‐
151 tive in previous ID3 versions. In fact, adding an RVA2 frame to a v2.3
152 tag confuses some MP3 players. Therefore, we are left with two choices
153 when trying to add volume adjustment information to an ID3 tag:
154 1. Go ahead and upgrade the tag to version 2.4, and use RVA2 tags.
156 This is the default behavior, in the hope that eventually MP3 play‐
157 ers will support v2.4 tags and this won't be a problem anymore.
158 2. Upgrade the tag to only version 2.3. Instead of RVA2, use an "XRVA"
160 tag with the same format as an RVA2 tag. This isn't a native frame,
161 but since it starts with an "X", it's considered experimental and
162 therefore legal, according to the ID3 spec. The --id3-compat option
163 turns on this behavior. The disadvantage of the first method is
164 that your MP3 player may no longer read the ID3 tags on your files.
165 Bug the author of your favorite MP3 player to support ID3v2.4 tags!
166 The disadvantage of the second method is that the XRVA frame is only
168 recognized by the xmms-rva plugin that is packaged with normalize. On
169 the other hand, I don't know of any MP3 players that recognize the RVA2
170 frame, either, so it may not make any difference.
171 The other option related to ID3 tags, --id3-unsync, is only necessary
173 for compatibility with old MP3 players that don't recognize ID3v2 tags
174 at all. If your MP3 player complains of garbage at the start of tagged
175 files, or is unable to play the files at all, turn this option on.
176 This option should never hurt, but if your MP3 player knows about ID3v2
177 tags, you don't need it.
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180 Note that your version of normalize must be compiled with MAD library
181 support to analyze MP3 file volume levels.
182
184 Chris Vaill <chrisvaill@gmail.com>
185
187 sox(1)
188 14 September 2005 NORMALIZE(1)