Implements MP3 320kbps download functionality using ffmpeg.wasm for
industry-standard encoding with libmp3lame.
Features:
- New MP3_320 quality option in download settings UI
- ID3v2.3 metadata writing (title, artist, album, cover art, ISRC, etc.)
- Non-blocking encoding via Web Worker to keep UI responsive
- Proper UTF-16 with BOM text encoding for international characters
- Album artist fallback to track artist (mirrors FLAC/M4A behavior)
- Automatic format detection for downloaded audio
- Year validation to prevent writing NaN to ID3 tags
Implementation:
- mp3-encoder.js: Main encoder module with worker orchestration
- mp3-encoder.worker.js: FFmpeg Web Worker for async encoding
- id3-writer.js: ID3v2.3 tag writer with synchsafe size encoding
- Updates to api.js, metadata.js, utils.js for MP3 support
- Vite config excludes @ffmpeg packages from dep optimization
Technical details:
- Uses @ffmpeg/ffmpeg (libmp3lame 320kbps CBR, 44.1kHz)
- FFmpeg binary lazy-loaded from CDN (~25MB, cached)
- Encoding runs in separate thread (non-blocking UI)
- Proper error handling with distinct encoding vs network errors
- Memory-efficient: transfers ArrayBuffer with zero-copy
Dependencies:
- @ffmpeg/ffmpeg ^0.12.10
- @ffmpeg/util ^0.12.1
- Removed: package-lock.json (project uses bun.lock)
Closes maintainer request to use ffmpeg.wasm instead of lamejs.
