mp3rgain: A drop-in Rust replacement for mp3gain with full command-line compatibility

[M-Igashi]

Hello!

I wanted to share a project that might be of interest to the mp3gain community.

Introducing mp3rgain

I've created mp3rgain, a drop-in replacement for mp3gain written in Rust. It aims for full command-line compatibility with the original mp3gain, so existing scripts and workflows continue to work without modification.

Command-line Compatibility

mp3rgain uses the same command-line syntax as mp3gain:

# These commands work identically in both tools
mp3gain -g 2 song.mp3       # original mp3gain
mp3rgain -g 2 song.mp3      # mp3rgain (drop-in replacement)

mp3gain -d 4.5 song.mp3     # apply dB
mp3rgain -d 4.5 song.mp3

mp3gain -s c song.mp3       # check/analyze
mp3rgain -s c song.mp3

Supported options: -g, -d, -s c, -p, -c, -q, -v, -h

Why a drop-in replacement?

The original mp3gain has been an invaluable tool for many years, but:

• Development appears to have stalled
• There are reports of compatibility issues with Windows 11
• Building from source can be challenging on modern systems
• Users need a tool that "just works" on modern platforms

Features

• Full CLI compatibility - Same command-line interface as mp3gain
• Lossless - Modifies global_gain field directly, no re-encoding
• Cross-platform binaries - macOS, Linux, Windows (x86_64 and ARM64)
• Zero dependencies - Single static binary, no external tools needed
• Memory safe - Written in Rust

Technical Compatibility

mp3rgain uses the same approach as the original mp3gain:

• Modifies the global_gain field in MP3 frame side information
• Each gain step = 1.5 dB (per MP3 specification)
• Supports MPEG 1/2/2.5 Layer III
• Handles VBR and CBR files
• Preserves ID3v2 tags

Current Status

Implemented:

• -g <i> - Apply gain in steps
• -d <n> - Apply gain in dB
• -s c - Check/analyze files
• -p - Preserve timestamp
• -c - Ignore clipping warnings
• -q - Quiet mode

Not yet implemented (contributions welcome!):

• -r - Track gain (requires ReplayGain analysis)
• -a - Album gain (requires ReplayGain analysis)
• -u - Undo from APEv2 tags

Links

• GitHub: https://github.com/M-Igashi/mp3rgain
• crates.io: https://crates.io/crates/mp3rgain
• Releases: https://github.com/M-Igashi/mp3rgain/releases (binaries for all platforms)

Looking for Contributors

I'm actively looking for contributors, especially those with experience in:

• Windows development and testing (especially Windows 11)
• ReplayGain implementation (-r and -a options)
• APEv2 tag handling (-u option)
• MP3 format internals

If anyone from the mp3gain community would like to contribute, test, or provide feedback, I would greatly appreciate it!

Installation

# Homebrew (macOS)
brew install M-Igashi/tap/mp3rgain

# Cargo (all platforms)
cargo install mp3rgain

# Or download binaries from GitHub Releases

[Sappharad]

Hello,

Thanks for sharing the link to your project. I can consider using it as a replacement someday, but right now this project uses the AACGain fork because users asked for that functionality. I would probably need to include both tools in order to retain that functionality.

While it's true that MP3Gain hasn't been actively developed for a long time, I think some of that just comes down to the fact that it already did what it was designed to do. The only thing they really can do at this point is fix bugs and modernize, which is sort of what you did here with a rewrite. I personally don't even use it anymore; almost all of the music I've purchased in the past 10 years has been mastered correctly with reasonable volume and the only exception that I found was mastered so poorly that I had to fix it destructively with Audacity because just adjusting the gain wasn't enough.

I'll leave this issue open because in the event I make an update I can try to switch over to this version.

Thanks again!