AC3 Audio Batch Converter

A standalone, Docker‑based batch converter that recursively scans a directory for media files and converts their audio tracks to AC‑3 while preserving video and subtitle streams. Designed for batch runs, cron jobs, and fully automated workflows. Includes multi‑threading, ETA tracking, persistent state, and detailed logging.

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Features

• Recursive directory scanning — processes all subfolders under a parent directory
• Multi‑threaded ffmpeg — uses all CPU cores by default or a user‑defined thread count
• Hash‑based identity tracking — prevents reprocessing even if files are renamed or moved
• Atomic file replacement — safe overwrite only after successful conversion
• Progress tracking — logs [current/total] for each file
• ETA calculation — estimates remaining time based on average processing speed
• Summary report — converted, skipped, failed, total time
• FORCE_REPROCESS flag — override the hash list and reprocess everything
• Detailed logging — logs written to a host‑mounted directory
• Environment‑variable driven — no command‑line arguments required
• Lightweight Alpine container — minimal footprint, fast startup

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Usage

Basic Run

Mount your media directory and pass it as TARGET_PATH:

docker run --rm \
  -e TARGET_PATH="/data" \
  -v /data:/data \
  ghcr.io/mxhdg/ac3-audio-converter:latest

With Logging

Mount a log directory to persist logs and the persistent hash list:

docker run --rm \
  -e TARGET_PATH="/data" \
  -v /data:/data \
  -v /DATA/AppData/ac3/logs:/logs \
  ghcr.io/mxhdg/ac3-audio-converter:latest

Logs will be written to:

/logs/batch_YYYY-MM-DD_HH-MM-SS.log

A persistent identity file is stored at:

/logs/processed_files.txt

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Environment Variables

Variable	Description	Default
TARGET_PATH	Parent directory to recursively scan	Required
THREADS	Override ffmpeg thread count	Auto‑detect CPU cores
FORCE_REPROCESS	Reprocess all files even if hashes match previous runs	false

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Supported File Types

The converter processes the following extensions:

• .mkv
• .mp4
• .mov
• .avi

You can modify this list in ac3convert.sh.

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How It Works

1. The container starts and reads TARGET_PATH.
2. It recursively finds all supported media files.
3. For each file:
   • Computes an MD5 hash to determine if it was processed in a previous run
   • Skips the file if the hash matches (unless FORCE_REPROCESS=true)
   • Converts audio to AC‑3 at 640k while copying video and subtitles
   • Writes a temporary file and atomically replaces the original
   • Computes a new hash and stores it in processed_files.txt
4. After each file, the script logs:
   • Progress ([current/total])
   • ETA based on average processing time
5. At the end, a summary report is written to the log.

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Example Cron Job

Run the converter nightly:

0 3 * * * docker run --rm \
  -e TARGET_PATH="/data" \
  -v /data:/data \
  -v /DATA/AppData/ac3/logs:/logs \
  ghcr.io/mxhdg/ac3-audio-converter:latest

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Development

Build Locally

docker build -t ac3-audio-converter .

Run Locally

docker run --rm \
  -e TARGET_PATH="/data" \
  -v /data:/data \
  ac3-audio-converter

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GitHub Actions (Tag‑Only Releases)

This project only publishes Docker images when a semantic version tag is pushed:

git tag v1.0.0
git push --tags

The workflow will:

• Build the container
• Tag it with semantic versions
• Push it to GHCR

No builds occur on normal commits.

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License

MIT License. Use freely and modify as needed.