mp3rgain

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

mp3rgain adjusts MP3 and AAC volume without re-encoding by modifying the global_gain field in each frame. This preserves audio quality while achieving permanent volume changes.

Features

• Lossless & Reversible: No re-encoding, all changes can be undone (MP3 and AAC)
• ReplayGain: Track and album gain analysis for MP3 and AAC/M4A
• 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

CLI (mp3rgain)

Platform	Command
macOS	brew install M-Igashi/tap/mp3rgain
Windows	winget install M-Igashi.mp3rgain
Arch Linux (AUR)	yay -S mp3rgain-bin
Debian/Ubuntu	sudo apt install ./mp3rgain_*_amd64.deb (download)
Nix/NixOS	nix profile install github:M-Igashi/mp3rgain
Cargo	cargo install mp3rgain

GUI (mp3rgui)

Platform	Command
macOS	brew install --cask M-Igashi/tap/mp3rgui
Windows	winget install M-Igashi.mp3rgui
Arch Linux (AUR)	yay -S mp3rgui

Binaries for all platforms are also available 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.

Install: See Installation above for Homebrew, Winget, and AUR options. Binaries are also available from GitHub Releases:

• mp3rgui-*-macos-universal.dmg (macOS)
• mp3rgui-*-linux-x86_64.tar.gz (Linux)
• mp3rgui-*-windows-x86_64.zip / mp3rgui-*-windows-arm64.zip (Windows)

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

xattr -cr /path/to/mp3rgui.app

This is not needed when installing via Homebrew.

Command-Line Options

Option	Description
-r	Apply Track gain (ReplayGain)
-a	Apply Album gain (ReplayGain)
-g <i>	Apply gain of i steps (1 step = 1.5 dB)
-d <n>	Modify target dB level (use with analysis)
-u	Undo gain changes
-k	Prevent clipping
-R	Process directories recursively
-n	Dry-run mode
-o [fmt]	Output format: text, json, tsv (default: tsv if no argument)

Run mp3rgain -h for the full list of options.

Documentation

• Roadmap - Development plans and upcoming features
• Security - Memory safety and CVE analysis
• Compatibility Report - Verification against original mp3gain
• Technical Comparison - Comparison with similar tools
• Use Cases - Integration examples (beets, headroom, etc.)

Why mp3rgain?

The original mp3gain has been unmaintained upstream since ~2015 (though distribution maintainers continue to apply security patches). mp3rgain is a modern, memory-safe replacement written in Rust.

mp3rgain implements the ReplayGain 1.0 algorithm (89 dB reference level) for full compatibility with the original mp3gain. Loudness values will differ from EBU R128/LUFS-based tools (foobar2000, loudgain, ffmpeg loudnorm).

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