roadmap.md

mp3rgain Roadmap

Current Status: v2.0.0 (Production Ready)

All core functionality complete:

• MP3 frame parsing (MPEG 1/2/2.5 Layer III)
• Global gain modification (MP3 and AAC)
• ID3v2 tag preservation
• VBR/CBR support
• CLI interface (apply/info/undo commands)
• ReplayGain analysis (track and album gain)
• AAC/M4A lossless bitstream gain adjustment and undo
• Full mp3gain command-line compatibility
• Cross-platform support (Windows, macOS, Linux)
• Stabilized library API with custom error types, builder pattern, submodules

Completed Milestones

v0.2.0 - Windows & Stability

• Windows 11 compatibility verification
• Windows ARM64 support
• Comprehensive test suite with real MP3 files
• Error handling improvements
• Homebrew tap formula

v0.3.0 - mp3gain Feature Parity

• ReplayGain analysis (track gain calculation)
• Album gain support
• -r (apply Track gain) flag compatibility
• -a (apply Album gain) flag compatibility
• -c (ignore clipping) flag
• -p (preserve original timestamp) flag

v0.4.0 - Extended Features

• Batch processing with recursive directory support
• Progress bar for large files
• JSON output format
• Dry-run mode
• TSV output format

v1.0.0 - AAC/M4A Support

• AAC/M4A ReplayGain analysis
• iTunes freeform tag writing
• Multi-track audio support (-i option)
• Production-ready release

v1.1.0 - Package Manager Expansion

• Scoop package (Windows)
• winget package (Windows Package Manager)
• AUR package (Arch Linux)
• Nix package
• Debian/Ubuntu package (.deb)

v1.2.0 - GUI Application & Bug Fixes

• Native GUI application (mp3rgui) for macOS, Linux, Windows
• Fix ReplayGain filter coefficients (v1.2.6)
• Improved Debian package build

v1.3.0 - Code Quality & Stability

• Code refactoring for better maintainability
• Documentation updates

v1.4.0 - Bug Fixes & mp3gain Compatibility

• Improved max amplitude detection (#51)
• Fixed global_gain range handling (#52)
• Handle last frame before APE/ID3 tags (#54)
• Fixed M4A info display (#55)
• Improved ReplayGain analysis accuracy (#48)
• Corrected ReplayGain calculation ~90dB offset (#50)

v1.5.0 - Debian Packaging

• Man page (docs/man/mp3rgain.1)
• cargo-deb configuration
• .deb package build in release workflow
• .deb package test workflow (Debian 12/13, Ubuntu 22.04/24.04)

v1.6.0 - MP4/M4A Hardening & GUI Fixes

• Hardened MP4/M4A metadata handling and file detection (#67)
• Atomic write (temp file + rename) for M4A tag updates
• ALAC file detection and proper rejection
• DRM-protected M4P file rejection
• Compatible brands list checking in ftyp box
• Improved ilst box management (empty container cleanup, NeedsIlst)
• Fixed chunk offset (stco/co64) updates with threshold-based adjustment
• Fixed GUI volume display to use 89 dB ReplayGain reference (#62)
• Code quality improvements (clippy, iterator patterns, helper extraction)

v1.7.0 - Library API Stabilization & AAC Parser (Issues #68, #64)

• Add #[non_exhaustive] to all public enums and structs
• Add missing standard trait implementations (PartialEq, Eq, Hash)
• Add Display trait implementations to all public types
• Add Serialize / Deserialize behind a serde feature flag
• Add ApeTag::iter() and ApeTag::len() methods
• Make MpegVersion / ChannelMode enums public with typed accessors on Mp3Analysis
• Add MaxAmplitudeResult struct and find_max_amplitude_detailed() function
• Add Channel::other() convenience method
• Remove unnecessary pub from filter_coeffs internal constants
• AAC bitstream parser for locating global_gain fields (Issue #64 Phase 1)
• AUR package for mp3rgui (GUI application)
• Automated AUR package publishing in release workflow

v2.0.0 - AAC Lossless Gain & Breaking API Changes (Issues #64, #68)

• AAC lossless bitstream gain adjustment (global_gain modification)
• AAC undo support (iTunes freeform metadata tags)
• HE-AAC/SBR support (base layer gain adjustment)
• Multi-track detection and warnings
• Custom error types (thiserror) replacing anyhow::Result
• MpegVersion / ChannelMode changed from String to enum
• Private struct fields with accessor methods
• GainOptions builder pattern
• Submodule organization (analysis, gain, ape, frame)

Upcoming Goals

Future Enhancements

• EBU R128 loudness analysis (--r128 option, ITU-R BS.1770 / LUFS-based)
• ReplayGain 2.0 support (--rg2 option, R128-based with -18 LUFS reference)
• Official Debian repository (ITP submission)
• Homebrew core inclusion (currently in tap)
• Fedora/RPM package
• Flatpak package
• FLAC support
• Ogg Vorbis support
• Integration with music players/taggers

Community Goals

• Reach 100 GitHub stars
• 5+ contributors
• Grow Windows user base
• Package availability in major package managers

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How to Contribute

See CONTRIBUTING.md for details on how to get involved.