<s>
MP3Gain	B-Language
is	O
an	O
audio	O
normalization	O
software	O
tool	O
.	O
</s>
<s>
The	O
tool	O
is	O
available	O
on	O
multiple	B-Operating_System
platforms	I-Operating_System
and	O
is	O
free	B-Application
software	I-Application
.	O
</s>
<s>
It	O
analyzes	O
the	O
MP3	B-Application
and	O
reversibly	O
changes	O
its	O
volume	O
.	O
</s>
<s>
The	O
volume	O
can	O
be	O
adjusted	O
for	O
single	O
files	O
or	O
as	O
album	O
where	O
all	O
files	O
would	O
have	O
the	O
same	O
perceived	O
loudness	B-Algorithm
.	O
</s>
<s>
MP3Gain	B-Language
first	O
computes	O
the	O
desired	O
gain	O
(	O
volume	O
adjustment	O
)	O
,	O
either	O
per	O
track	O
or	O
per	O
album	O
,	O
using	O
the	O
ReplayGain	O
algorithm	O
.	O
</s>
<s>
It	O
then	O
modifies	O
the	O
overall	O
volume	O
scale	O
factor	O
in	O
each	O
MP3	B-Application
frame	O
,	O
and	O
writes	O
undo	O
information	O
as	O
a	O
tag	O
(	O
in	O
APEv2	O
,	O
or	O
ID3v2	O
format	O
)	O
making	O
this	O
a	O
reversible	O
process	O
.	O
</s>
<s>
MP3Gain	B-Language
does	O
not	O
introduce	O
any	O
digital	O
generation	O
loss	O
because	O
it	O
does	O
not	O
decode	B-Device
and	I-Device
re-encode	I-Device
the	O
file	O
.	O
</s>
<s>
MP3Gain	B-Language
is	O
unable	O
to	O
change	O
the	O
volume	O
on	O
AAC	O
or	O
MP4	O
files	O
.	O
</s>
<s>
A	O
mod	O
called	O
AACGain	O
exists	O
that	O
can	O
be	O
used	O
as	O
super-set	O
drop-in	O
replacement	O
in	O
most	O
front-ends	O
originally	O
created	O
for	O
MP3Gain	B-Language
.	O
</s>
