MP3Gain first computes the desired gain (volume adjustment), either per track or per album, using the ReplayGain algorithm. It then modifies the overall volume scale factor in each MP3 frame, and writes undo information as a tag (in APEv2, or ID3v2 format) making this a reversible process. The scale factor modification can be reversed using the information in the added tag and the tag may be removed. MP3Gain does not introduce any digital generation loss because it does not decode and re-encode the file.
