Kontainer

A media file format generator/parser that exposes a React-like API.

Kontainer aims to fully support the MP4 (ISO Base Media file format: ISO/IEC 14496-12) and WebM file format. The library can be used on Node.js and in the browser.

Install

Overview

API

A media file like MP4 and WebM is composed of nested objects. In Kontainer, each object, e.g. MP4 Box, is represented as a KontainerElement which is similar to the ReactElement.

The actual media data (audio and video chunks) and the metadata are represented as a props object and passed to the KontainerElement as its attributes.

import Kontainer from 'kontainer-js';

export default class MP4 {

  constructor(width, height) {
    Kontainer.use('mp4'); // format (mp4|webm) needs to be set before any API call
    this.width = width;
    this.height = height;
  }

  render() {
    return (
    <file>
      <ftyp majorBrand="isom" />
      <moov>
        <mvhd creationTime={new Date()} modificationTime={new Date()} timeScale={1} nextTrackId={4} />
        <trak>
          <tkhd creationTime={new Date()} modificationTime={new Date()} trackId={1} width={this.width} height={this.height} />
          <mdia>
            ...
          </mdia>
        </trak>
      </moov>
    </file>
    );
  }
}

The above code can be transpiled into the calls to createElement() using babel and a dedicated plugin.

    // Kontainer.createElement()
    //   Accepts: type, props, children...
    //   Returns: KontainerElement
    return Kontainer.createElement('file', null,
      Kontainer.createElement('ftyp', {majorBrand: 'isom'}),
      Kontainer.createElement('moov', null,
        Kontainer.createElement('mvhd', {creationTime: new Date(0), modificationTime: new Date(), timeScale: 1, nextTrackId: 4}),
        Kontainer.createElement('trak', null,
          Kontainer.createElement('tkhd', {creationTime: new Date(0), modificationTime: new Date(), trackId: 1, width: 640, height: 480}),
          Kontainer.createElement('mdia', null,
            ...
            // KontainerElement can be a child of other elements to compose a large nested tree.
          )
        )
      )
    );

Once an element is obtained, it can be serialized into a byte stream using render().

    // Kontainer.render()
    //   Accepts: KontainerElement
    //   Returns: Buffer (in node) or ArrayBuffer (in browser) that contains a media stream
    buffer = Kontainer.render(element);

On the other hand, you can create a KontainerElement from a byte stream.

    // Kontainer.createElementFromBuffer()
    //   Accepts: Buffer (in node) or ArrayBuffer (in browser) that contains a media stream [, offset=0]
    //   Returns: KontainerElement.
    element = Kontainer.createElementFromBuffer(buffer, offset);

You can also create your hook and process a byte stream progressively. (This works only for Node.js)

  const input = fs.createReadStream('./test.mp4');
  const transform = Kontainer.transform((type, props, children) => {
    if (type === 'tkhd') {
      // Change video dimensions
      props.width /= 2;
      props.height /= 2;
    }
  });
  input.pipe(transform).pipe(process.stdout);

JSX

To transpile JSX into createElement() calls together with your ES.next code, you need to install babel and its plugins.

$ npm install babel-cli
$ npm install babel-preset-es2015
$ npm install babel-plugin-transform-kontainer-js

Put a .babelrc file in the source directories that contain JSX.

{
  "presets": ["es2015"],
  "plugins": ["transform-kontainer-js"]
}

Then use the babel command to transpile the code.

$ babel src/ -d dist/

See the plugin code for the details.

CLI

A simple parser for displaying the structure of a media file.

Usage:
    kontainer filePath [options]

Example:
    kontainer /path/to/file
    cat /path/to/file | kontainer

Options:
  -h, --help    Print help
  -v, --version Print version

Development

// Install
$ git clone git@github.com:kuu/Kontainer.git
$ cd Kontainer
$ npm install

// Test
$ npm test

// Build client libs
$ npm run build
// --> ./lib/kontainer.deb.js (uncompressed with debug messages)
// --> ./lib/kontainer.js (uncompressed)
// --> ./lib/kontainer.min.js (compressed)
// --> ./lib/kontainer.map.js (source map)