flac2mp3-watcher

A lightweight Docker container that watches a directory tree for FLAC files and automatically converts them to MP3 (320k CBR) in-place. The source FLAC file is deleted after a successful conversion.

Built on Alpine Linux with ffmpeg and inotify-tools. Unraid-friendly (runs as UID 99 / GID 100).

Docker Hub: dasaod/flac2mp3

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Features

• Watches recursively via inotify — reacts immediately, no polling
• Converts FLAC → MP3 at 320k CBR, preserving metadata tags
• Deletes the original FLAC after a successful conversion
• Initial scan on startup (converts any existing FLAC files)
• Skips files where an up-to-date MP3 already exists
• Log rotation (configurable size and number of backups)
• Healthcheck: verifies inotifywait is running
• Unraid-friendly: runs as nobody:users (99:100), respects umask

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Quick Start

docker run -d \
  --name flac2mp3-watcher \
  -e ROOT=/media \
  -v /path/to/your/music:/media \
  -v /path/to/appdata/flac2mp3:/config \
  dasaod/flac2mp3:latest

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Environment Variables

Variable	Default	Description
ROOT	/media	Directory to watch (must be mounted)
UMASK_VAL	002	File creation umask
LOGFILE	/config/flac2mp3-watcher.log	Log file path
LOG_MAX_MB	10	Max log size in MB before rotation
LOG_BACKUPS	3	Number of rotated log files to keep

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Volumes

Container path	Purpose
/media	Music directory to watch (mount your FLAC folder here)
/config	Log file storage

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Unraid Template

Repository:   dasaod/flac2mp3:latest
Network:      Bridge

Volumes:
  /path/to/music        → /media   (RW)
  /mnt/user/appdata/flac2mp3 → /config  (RW)

Environment:
  ROOT        = /media
  UMASK_VAL   = 002
  LOGFILE     = /config/flac2mp3-watcher.log
  LOG_MAX_MB  = 10
  LOG_BACKUPS = 3

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Build

# Build locally
docker build -t dasaod/flac2mp3:1.2 -t dasaod/flac2mp3:latest .

# Push to Docker Hub
docker push dasaod/flac2mp3:1.2
docker push dasaod/flac2mp3:latest

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How It Works

1. On startup, an initial scan converts all existing .flac files under ROOT
2. inotifywait then watches for new or updated files (CLOSE_WRITE, CREATE, MOVED_TO)
3. When a .flac file is detected, ffmpeg converts it to .mp3 (320k CBR) in the same directory
4. On success, the original .flac is deleted
5. Log rotation runs automatically when the log exceeds LOG_MAX_MB

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Changelog

1.2

• Fix: log rotation now called on every log entry
• Fix: relative paths from inotify always resolved to absolute
• Improved: case-insensitive FLAC extension matching via nocasematch

1.1

• Added log rotation (LOG_MAX_MB, LOG_BACKUPS)
• Added Dockerfile with embedded watcher.sh (no install on start)
• Added Healthcheck
• Improved path handling

1.0

• Initial release

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Mitwirkende

Dieses Projekt wurde in Zusammenarbeit mit Claude (Sonnet 4.6) von Anthropic entwickelt und iterativ ausgebaut.
Der überwiegende Teil des Codes, der Architektur und der Dokumentation wurde durch KI generiert und gemeinsam verfeinert.

Rolle	Person / Tool
Projektidee, Anforderungen & Tests	DasAoD
Code, Architektur, Dokumentation	Claude (Anthropic)

License

MIT