audible-util

audible-util is a command-line utility for converting Audible .aaxc audiobook files into standard audio formats (MP3, WAV, FLAC) using a voucher file generated by audible-cli. It leverages ffmpeg and ffprobe for decoding and metadata extraction, providing a robust and extensible tool for audiobook enthusiasts and archivists.

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Features

• Converts Audible .aaxc files to MP3, WAV, or FLAC.
• Uses voucher files from audible-cli for decryption.
• Automatically infers voucher file if not specified.
• Extensible output format system (easy to add new formats).
• Planned support for splitting output into chapters/segments.
• Progress indication and detailed logging.
• Helpful error messages and validation.

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Installation

Prerequisites

• Rust (edition 2021 or later): Install Rust
• ffmpeg and ffprobe: Must be installed and available in your PATH.
  • The tool checks for these dependencies before any processing and will provide a clear error if they are missing.
  • On Ubuntu/Debian:

    sudo apt-get install ffmpeg
    

  • On macOS (Homebrew):

    brew install ffmpeg
    

  • On Windows: Download from ffmpeg.org and add to your PATH.

Build from Source

Clone the repository and build with Cargo:

git clone https://github.com/yourusername/audible-util.git
cd audible-util
cargo build --release

The binary will be in target/release/audible-util.

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Usage

All user-provided arguments and files are validated before any processing begins. The tool will check:

• That the input .aaxc file exists, is readable, and has the correct extension.
• That the voucher file exists and is readable (if provided or inferred).
• That the output directory exists and is writable (if a custom output path is provided).
• That ffmpeg and ffprobe are installed and available in your PATH.

If any of these checks fail, you will receive a clear, actionable error message.

Basic Command

audible-util --aaxc-path /path/to/book.aaxc --voucher-path /path/to/book.voucher

If --voucher-path is omitted, the tool will look for a voucher file named <book>.voucher in the same directory as the .aaxc file.

CLI Options

Option	Short	Type	Required	Description
--aaxc-path	-a	Path	Yes	Path to the input .aaxc file
--voucher-path		Path	No	Path to the voucher file (from audible-cli). Inferred if not provided.
--output-path		Path	No	Output file path. Defaults to <album>.<ext> in current directory.
--split	-s	Flag	No	(Planned) Split output into chapters/segments. Currently not implemented.
--output-type		mp3/wav/flac	No	Output file type. Defaults to mp3.

Example: Convert to FLAC with custom output path

audible-util --aaxc-path book.aaxc --voucher-path book.voucher --output-type flac --output-path mybook.flac

Example: Use default voucher and output

audible-util --aaxc-path book.aaxc

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Voucher File Requirements

• The voucher file must be a JSON file generated by audible-cli.
• The file is validated for required fields and structure.
• If invalid or missing, the tool will display a detailed error message.

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Output Formats

• MP3 (default): --output-type mp3
• WAV: --output-type wav
• FLAC: --output-type flac

The output format system is extensible. To add a new format, implement the OutputFormat trait in src/cli.rs.

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Splitting Functionality

• The --split flag is present but not yet implemented.
• Planned: Split output into chapters or segments using metadata.
• To extend: Implement logic to parse chapter metadata and invoke ffmpeg for each segment, using the OutputFormat trait for extensibility. See code comments in src/main.rs for guidance.

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Troubleshooting & Common Errors

• "Input file does not exist" The path provided to --aaxc-path does not point to a file. Check the file path and try again.

• "Input file does not have a .aaxc extension" The input file must have a .aaxc extension.

• "Input file is not readable" Check file permissions for the input file.

• "Voucher file does not exist" / "Voucher file is not readable" Check the voucher file path and permissions.

• "Output directory does not exist" / "Output directory is not writable" Ensure the output directory exists and is writable, or specify a different output path.

• "Required external tool 'ffmpeg'/'ffprobe' is not installed or not found in your PATH" Install the missing tool and ensure it is available in your system PATH. See Prerequisites above.

• "Could not get file stem from the input file path" Ensure the --aaxc-path points to a valid .aaxc file.

• "Failed to open voucher file" Check that the voucher file exists and is readable.

• "Failed to parse voucher file" The voucher file must be valid JSON generated by audible-cli.

• "Failed to start ffmpeg/ffprobe" Ensure ffmpeg and ffprobe are installed and available in your PATH.

• "ffmpeg/ffprobe failed with error" The input file may be corrupt or not a valid Audible AAXC file.

• For verbose logs, set the RUST_LOG environment variable:

  RUST_LOG=info audible-util --aaxc-path book.aaxc
  

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Contribution Guidelines

Contributions are welcome! To contribute:

1. Fork the repository.
2. Create a new branch for your feature or bugfix.
3. Write clear, well-documented code and update/add tests if applicable.
4. Submit a pull request with a detailed description.

For major changes or questions, please open an issue first to discuss your proposal.

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Contact

For questions, issues, or suggestions, please open an issue on the GitHub repository or contact the maintainer at your.email@example.com.

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License

This project is licensed under the MIT License.