[slowfrog]

Metaflac creates tags which look something like this:

REPLAYGAIN_ALBUM_PEAK=0.97946167
REPLAYGAIN_ALBUM_GAIN=+0.81 dB
REPLAYGAIN_TRACK_PEAK=0.54107666
REPLAYGAIN_TRACK_GAIN=+4.79 dB
REPLAYGAIN_REFERENCE_LOUDNESS=89.0 dB

Thanks