About mp3rgain
mp3rgain changes the volume of MP3 and AAC (M4A/MP4 and raw ADTS) files without re-encoding, by rewriting the global_gain field stored in each frame, so audio quality is preserved.
It analyzes track and album loudness with ReplayGain 1.0 by default (mp3gain-identical values), or ReplayGain 2.0 and EBU R128 as options, writes REPLAYGAIN_* tags, and stores an undo tag that -u uses to revert gain changes.
The command-line options, TSV output and undo tag follow mp3gain, so existing scripts keep working.
