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, the Vorbis plugin (in_vorbis) 1.2b22 for WinAmp supports this, and XMMS 1.2.8 will also support it (there is a patch available for earlier versions of XMMS available; however, it does not support the new format of the suggestions this version of VorbisGain implements).
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.)
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.)
The implementation of ReplayGain support in a player is quite easy actually. At http://sjeng.org/ftp/vorbis/ you can find a patch for XMMS 1.2.6 that shows how it can be done. Adding support for the new format (the old format should be supported as well) is left as an excercise for the reader. :)
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>
.