MP4 Box Explorer

MP4 Box Explorer is a readonly VS Code custom editor for inspecting MP4, M4S, and fragmented MP4 files. It parses ISO Base Media File Format box structure with mp4box and displays the result as a searchable, expandable tree inside VS Code.

Use it when you need to quickly inspect media file structure, offsets, sizes, nested boxes, and parsed field values without leaving your editor.

Features

• Opens .mp4 and .m4s files in an MP4 Box Preview custom editor.
• Shows box type, box name, size, byte offset, parsed fields, and nested child boxes.
• Filters boxes by type, name, property name, property value, or parsed binary value.
• Expands and collapses the full box tree for faster navigation.
• Summarizes binary fields as hex, ASCII, integer values, and FourCC guesses where useful.
• Copies parsed property values or raw hex values from the preview.
• Uses VS Code theme colors so the preview follows your active editor theme.

Supported Files

• .mp4
• .m4s

The extension is intended for MP4-family files that can be parsed by mp4box, including fragmented MP4 content.

Installation

Install MP4 Box Explorer from the Visual Studio Code Marketplace, then open an .mp4 or .m4s file in VS Code.

If you are installing a local .vsix build instead:

code --install-extension mp4-box-explorer-<version>.vsix

Usage

1. Open an .mp4 or .m4s file in VS Code.
2. If VS Code prompts for an editor, choose MP4 Box Preview.
3. Use Expand all, Collapse all, and the filter field to navigate the parsed box tree.
4. Use field-level Copy actions to copy displayed values or raw hex values.

Privacy

MP4 Box Explorer reads the selected media file from your local workspace so it can parse and render the box tree. It does not send file contents, file names, paths, telemetry, or usage data to any external service.

Known Limitations

• The preview is readonly; it does not edit, repair, rewrite, or export media files.
• Parsing runs in the extension host and reads the selected file into memory, so very large files may be slow or memory-intensive.
• Parser coverage and box field names come from mp4box.
• Invalid or partially supported files may only show boxes parsed before a parse warning occurred.

Development

Requirements:

• Node.js compatible with the dependencies in package-lock.json.
• VS Code 1.100.0 or newer.

Common commands:

npm install
npm run check
npm run compile
npm run watch
npm run package

To publish the extension, make sure you are authenticated for the REDspace publisher and run:

npm run publish

Debugging:

1. Open this folder in VS Code.
2. Run npm install.
3. Start the Run Extension debug configuration.
4. In the Extension Development Host window, open an .mp4 or .m4s file.

Contributing

Contributions are welcome. See CONTRIBUTING.md for development setup, verification steps, and pull request guidelines.

License

MIT. See LICENSE.