Replay Gain - A Proposed Standard


The Problem

Not all CDs sound equally loud. The perceived loudness of mp3s is even more variable. Whilst different musical moods require that some tracks should sound louder than others, the loudness of a given CD has more to do with the year of issue or the whim of the producer than the intended emotional effect. If we add to this chaos the inconsistent quality of mp3 encoding, it's no wonder that a random play through your music collection can have you leaping for the volume control every other track.

The solution

There is a remarkably simple solution to this annoyance, and that is to store the required replay gain for each track within the track. This concept is called "MetaData" data about data. It's already possible to store the title, artist, and CD track number within an mp3 file using the ID3 standard. The later ID3v2 standard also incorporates the ability to store a track relative volume adjustment, which can be used to "fix" quiet or loud sounding mp3s.

However, there is no consistent standard by which to define the appropriate replay gain which mp3 encoders and players agree on, and no automatic way to set the volume adjustment for each track until now.

The Replay Gain proposal sets out a simple way of calculating and representing the ideal replay gain for every track and album. Read on to find out more, or see what's new.


This proposal was published on July 10th 2001. Help with player and file format support is needed.

The work that still needs to be done is discussed in the Technical Outline. Current progress is reported under Updates.

Comments or questions (I welcome both) may be directed to the author: Areas where I specifically need help to get this proposal off the ground are mentioned under "Suggestions and further work" at the bottom of each page.

Any Discussions that arise will probably be held in the HydrogenAudio forum, in the General section.