
INTRODUCTION
------------

When listening to Ogg Vorbis (or MP3) files on your computer, you may have
noticed that some songs are louder than others. To a degree, this can be
what the artist or producer intended, at least when comparing songs from the
same CD. However, when (randomly) listening to songs from different CDs, the
sound level can vary quite much, so much that you need to adjust the volume
every now and then, to get a comfortable sound level. Wouldn't it be nice if
that could be handled automatically?

This is where VorbisGain comes in. It calculates a percieved sound level of
an Ogg Vorbis file using the ReplayGain algorithm. VorbisGain then stores in
the comments (tags) in the file a suggestion on how the volume should be 
changed during playback, to get a uniform sound level. However, this only 
solves half the problem; the player application needs to act on that
suggestion for it to be any useful.

PLAYER SUPPORT
--------------

As VorbisGain only stores suggested volume changes in the files, the player
application need to read these suggestions and act upon them. As of this
writing, Winamp, foobar2000, XMMS and other major players support this.

INSTALLATION
------------

Run './configure' followed by 'make' (use './configure --help' to see
configuration options). Then use 'make install' to install it (or just copy
the vorbisgain executable to a directory of your choice).

For details on usage, please see the man page (or vorbisgain.txt, if you are
on a Windows platform).

ACKNOWLEDGEMENTS
----------------

VorbisGain uses the ReplayGain algorithm, which was created by David
Robinson. The implementation of that algorithm was written by Glen Sawyer
and Frank Klemm. Using some example code from Ogg Vorbis, the first versions
of VorbisGain (then called ReplayGain) was written by Gian-Carlo Pascutto,
who also wrote a patch for XMMS, adding support for the new tags. Better
Windows support and various new features where then added by Magnus
Holmgren, with help from Gian-Carlo Pascutto. Magnus Holmgren also updated
the XMMS patch to include support for the new tags (this patch has been sent
to the XMMS developers, but is otherwise not available).

For more information about ReplayGain, see http://www.replaygain.org/
(However, note that the ReplayGain web site might not be up to date when it
comes to application support for ReplayGain.)
One notable update is that VorbisGain uses a reference level of 89dB, 
and not 83dB.

NOTES
-----

Please note that as of VorbisGain 0.30, the volume change suggestions are
stored in a new format. The following is an example on how it can look:

    REPLAYGAIN_TRACK_GAIN=-7.03 dB
    REPLAYGAIN_TRACK_PEAK=1.21822226
    REPLAYGAIN_ALBUM_GAIN=-6.37 dB
    REPLAYGAIN_ALBUM_PEAK=1.21822226

Earlier versions stored the information like this:

    RG_RADIO=-7.03 dB
    RG_PEAK=1.21822226
    RG_AUDIOPHILE=-6.37 dB

(The lack of an album peak was one reason to change the format; it was also
desirable to make the tag names easier to understand.)

TODO
----

Although a configure script is used, it has not been widely tested. As of
this writing, it is only known to work on (a certain distribution of) Linux.
Corrections to handle other platforms are welcomed. Please send them to
Magnus Holmgren <lear@algonet.se> and/or Gian-Carlo Pascutto
<gcp@sjeng.org>
.
