With lossy files, it will insert a tag into the file that tells the ReplayGain supporting player how loud it is, so that the player can adjust it without having any loss of quality in the original file. The drawback is that you have to have a player that supports it. There is one neat thing that mp3 provides, which is scale factor, so you CAN actually adjust the loudness of an mp3 file without re-encoding it. And it will play back properly on any mp3 player without the need for ReplayGain support. Scale factor changes and ReplayGain can also co-exist together just fine, as it happens from the mp3Gain software. I haven't had a chance to try R128Gain yet to see if it supports that "hat trick" but I certainly hope it does.Goat Rodeo Cowboy said:
It's possible to simply change the gain, requantize to the target output bit depth, and save another file, but there is of course always the potential for audible quality loss if you're going to 16bit int.