M-Igashi.mp3rgain 1.4.0

Lossless MP3 volume adjustment - a modern mp3gain replacement written in Rust

mp3rgain adjusts MP3 volume without re-encoding by modifying the global_gain field in each frame's side information. This preserves audio quality while achieving permanent volume changes. Features include ReplayGain analysis, AAC/M4A support, and full mp3gain command-line compatibility.