The use of Replay Gain is an option in flac and other file formats.
The idea of Replay Gain is to calculate a volume adjustment that players (hardware and software) can use to even out jarring volume differences between songs, when they are playing the encoded files.
- It makes the most sense to use in a mix of singles, where the songs might have widely varying volumes. That's track
replaygain - it's helpful when playing a mix, because the sound levels between tracks pulled from different albums or shows can vary a lot.
- But if you're doing a whole album or show, you very much want to preserve the volume differences between songs - keep the quieter songs quieter. Otherwise, you get weird volume jumps between tracks, and the songs that are supposed to be softer get oddly amplified. So album replaygain will check the whole album / show (all the files) and apply an equal volume adjustment to all. That's album
The volume adjustment is stored as a short hexadecimal number in the tags for the file. So if you see an odd several digit number made up of digits 0-9 and letters A-F, that may be a Replay Gain tag.
It's an ingenious system, because it doesn't actually change the music data - it just calculates a volume adjustment that's stored in the file "header" or tags. The player reads that and applies a volume adjustment to the music when the encoded file is played.
Note that including the ReplayGain
information in the flac file normally does not change the audio data. If you use flac.exe or FlacFrontend
to decode a flac file, it ignores the ReplayGain
information. (However, if you use a wav output plugin for a player (such as WinAmp
), it will probably write out the altered audio data.)
The short answer on whether to use Replay Gain when you are encoding seeds is, it's your call. If you have a fast computer, it doesn't add much processing time. If you do decide to use Replay Gain when you're encoding a show, be sure to use the "Treat input files as one album" option, and encode the whole show at once, to preserve the volume levels of each track relative to others in the show.
If you'd rather, you can safely ignore that option and leave it un-checked. Most people won't benefit from it - it's only used when flacs are played from the flac file, and a quick twist of the volume control does just as well for those listening to a whole show. It's really more use for mixes of single tracks.
Replaygain is described more at the [HydrogenAudio ReplayGain site]