libpgs

libpgs-js

This library renders the graphical subtitles format PGS (.sup files) in the browser.

Work in progress

This project is still in progress. It should be able to play 99% of Blu-ray subtitles (Yes, I made that number up). But some rare used PGS features - like cropping - aren't implemented yet.

If you know a movie or show that is using the cropping feature, please let me know!

Requirements

This library requires the following web features:

• Web Worker API
• OffscreenCanvas (optional sine 0.5.0)
  • If available rendering is done inside the web-worker. If transferControlToOffscreen isn't supported a fallback is used where the subtitles are renderer on the main thread.

Usage

Install the package via npm:

npm i --save libpgs

Create with default canvas

The PGS renderer will create a default canvas element next to the video element:

const videoElement = document.getElementById('video-element');
const pgsRenderer = new libpgs.PgsRenderer({
  // Make sure your bundler keeps this file accessible from the web!
  workerUrl: './node_modules/libpgs/dist/libpgs.worker.js', 
  video: videoElement,
  subUrl: './subtitle.sup'
});

The created default canvas element is using a style definition like this:

position: absolute;
left: 0;
top: 0;
right: 0;
bottom: 0;
width: '100%';
height: '100%';
pointer-events: 'none';
object-fit: 'contain';

This only works if the video element is stretched in its parent and if the parent is using the css position property.

<div style="position: relative">
    <video id="video-element" src="./video.mp4"></video>
</div>

Create with custom canvas

It is also possible to provide a custom canvas element and position it manually:

const videoElement = document.getElementById('video-element');
const canvasElement = document.getElementById('canvas-element');
const pgsRenderer = new libpgs.PgsRenderer({
  // Make sure your bundler keeps this file accessible from the web!
  workerUrl: './node_modules/libpgs/dist/libpgs.worker.js',
  video: videoElement,
  canvas: canvasElement,
  subUrl: './subtitle.sup'
});

Time offset

You can also adjust time offset between video and subtitle:

// Rendering the subtitle 3 seconds in advance of the video
pgsRenderer.timeOffset = 3.0;

Destroy

Make sure to dispose the renderer when leaving:

// Releases video events and removes the default canvas element
pgsRenderer.dispose();

Licence

MIT License