MP3Gain is free software cross-platform audio normalizer software: it analyzes the MP3 and losslessly (reversibly) modifies files so that they have the same perceived volume. It is an implementation of Replay Gain.
MP3Gain can modify files in two ways:
MP3Gain can modify files in two ways:
- write metadata;
- modify MP3 data, writing undo information as metadata.
In both cases, it first computes the desired gain (volume adjustment), either per track or per album, using the Replay Gain algorithm.
In the first instance, it simply writes this as a tag (in APEv2 format), which can be read by other applications that implement Replay Gain.
In the second instance, it modifies the overall volume (scale factor) in each MP3 frame, and writes undo information as a tag. Note that this is completely reversible. By subtracting the modification that was done and removing the tag, it does not introduce any digital generation loss because it does not decode and re-encode the file.
