mp3rgain

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

• Lossless & Reversible: No re-encoding, all changes can be undone
• ReplayGain: Track and album gain analysis with AAC/M4A support
• Zero dependencies: Single static binary (no ffmpeg, no mp3gain)
• Cross-platform: macOS, Linux, Windows (x86_64 and ARM64)
• mp3gain compatible: Drop-in replacement with identical CLI
• GUI Application: Native desktop app for drag-and-drop workflow

Installation

macOS

brew install M-Igashi/tap/mp3rgain

Windows (recommended)

winget install M-Igashi.mp3rgain

Windows (alternative)

scoop bucket add mp3rgain https://github.com/M-Igashi/scoop-bucket
scoop install mp3rgain

Linux

# Arch Linux (AUR)
yay -S mp3rgain

# Nix/NixOS
nix profile install github:M-Igashi/mp3rgain

Cargo

cargo install mp3rgain

Manual Download

Download binaries from GitHub Releases.

Quick Start

# Normalize a single track (ReplayGain)
mp3rgain -r song.mp3

# Normalize an album
mp3rgain -a *.mp3

# Manual gain adjustment (+3.0 dB)
mp3rgain -g 2 song.mp3

# Undo changes
mp3rgain -u song.mp3

# Show file info
mp3rgain song.mp3

GUI Application

A native GUI application (mp3rgui) is available for users who prefer a graphical interface.

Features: Drag-and-drop, track/album analysis, one-click gain application, clipping warnings, progress indicators.

Download: GitHub Releases

• mp3rgui-macos-universal.tar.gz (macOS)
• mp3rgui-linux-x86_64.tar.gz (Linux)
• mp3rgui-windows-x86_64.zip (Windows)

macOS users: If you see "mp3rgui cannot be opened" warning, run:

xattr -cr /path/to/mp3rgui

Command-Line Options

Run mp3rgain -h for the full list of options.

Integration

beets

mp3rgain works as a drop-in replacement for mp3gain in the beets replaygain plugin:

# config.yaml
replaygain:
  backend: command
  command: mp3rgain

Documentation

• Security - Security improvements over original mp3gain (CVE-2021-34085, CVE-2019-18359)
• Compatibility Report - Verification against original mp3gain
• Technical Comparison - Comparison with similar tools

Why mp3rgain?

The original mp3gain has been unmaintained since ~2015. mp3rgain is a modern, memory-safe replacement that works on current systems including Windows 11, macOS, and Linux.

ReplayGain Algorithm

mp3rgain implements the original ReplayGain 1.0 algorithm, the same as the classic mp3gain/aacgain:

• Equal-loudness filter (Yule-Walker + Butterworth high-pass)
• RMS calculation in 50ms windows
• 95th percentile statistical analysis
• 89 dB reference level

This is a deliberate choice to maintain full compatibility with the original mp3gain. Loudness values will differ from tools using EBU R128/LUFS-based analysis (such as foobar2000's ReplayGain scanner, loudgain, or ffmpeg's loudnorm filter), which use a -23 LUFS reference level.

Library Usage

use mp3rgain::{apply_gain, analyze};
use std::path::Path;

let frames = apply_gain(Path::new("song.mp3"), 2)?;  // +3.0 dB
let info = analyze(Path::new("song.mp3"))?;

Contributing

Contributions welcome! See CONTRIBUTING.md.

License

MIT License - see LICENSE.

See Also

• Original mp3gain
• headroom - DJ audio loudness optimizer