sumonst21 / javascriptsubtitlesoctopus

Displays subtitles in .ass format via JavaScript. Supports all SSA/ASS features, easily integrates with HTML5 videos.

SubtitlesOctopus displays subtitles in .ass format and easily integrates with HTML5 videos. It supports all SSA/ASS features and fully compatible with libass.

ONLINE DEMO / other examples with demo

Features

• Supports all SSA/ASS features
• Supports any fonts
• Works fast (because uses WebAssembly with fallback to asm.js if it's not available)
• Uses Web Workers thus video and interface doesn't lag even on "heavy" subtitles (working in background)
• Doesn't use DOM manipulations and render subtitles on single canvas
• Fully compatible with libass
• Easy to use - just connect it to video element

Included Libraries

• expat
• fontconfig
• freetype
• fribidi
• harfbuzz

Usage

To start using SubtitlesOctopus you only need to instantiate a new instance of SubtitlesOctopus and specify its Options.

var options = {
    video: document.getElementById('video'), // HTML5 video element
    subUrl: '/test/test.ass', // Link to subtitles
    fonts: ['/test/font-1.ttf', '/test/font-2.ttf'], // Links to fonts (not required, default font already included in build)
    workerUrl: '/libassjs-worker.js' // Link to file "libassjs-worker.js"
};
var instance = new SubtitlesOctopus(options);

After that SubtitlesOctopus automatically "connects" to your video and it starts to display subtitles. You can use it with any HTML5 player.

See other examples.

Using only with canvas

You're also able to use it without any video. However, that requires you to set the time the subtitles should render at yourself:

var options = {
    canvas: document.getElementById('canvas'), // canvas element
    subUrl: '/test/test.ass', // Link to subtitles
    fonts: ['/test/font-1.ttf', '/test/font-2.ttf'], // Links to fonts (not required, default font already included in build)
    workerUrl: '/libassjs-worker.js' // Link to file "libassjs-worker.js"
};
var instance = new SubtitlesOctopus(options);
// And then...
instance.setCurrentTime(15); // Render subtitles at 00:15 on your canvas

Changing subtitles

You're not limited to only display the subtitle file you referenced in your options. You're able to dynamically change subtitles on the fly. There's three methods that you can use for this specifically:

• setTrackByUrl(url): works the same as the subUrl option. It will set the subtitle to display by its URL.
• setTrack(content): works the same as the subContent option. It will set the subtitle to dispaly by its content.
• freeTrack(): this simply removes the subtitles. You can use the two methods above to set a new subtitle file to be displayed.

var instance = new SubtitlesOctopus(options);

// ... we want to change the subtitles to the Railgun OP
instance.setTrackByUrl('/test/railgun_op.ass');

Cleaning up the object

After you're finished with rendering the subtitles. You need to call the instance.dispose() method to correctly dispose of the object.

var instance = new SubtitlesOctopus(options);

// After you've finished using it...

instance.dispose();

Options

When creating an instance of SubtitleOctopus, you can set the following options:

• video: The video element to attach listeners to. (Optional)
• canvas: The canvas to render the subtitles to. If none is given it will create a new canvas and insert it as a sibling of the video element (only if the video element exists). (Optional)
• subUrl: The URL of the subtitle file to play. (Require either subUrl or subContent to be specified)
• subContent: The content of the subtitle file to play. (Require either subContent or subUrl to be specified)
• workerUrl: The URL of the worker. (Default: libassjs-worker.js)
• fonts: An array of links to the fonts used in the subtitle. (Optional)
• availableFonts: Object with all available fonts - Key is font name in lower case, value is link: {"arial": "/font1.ttf"} (Optional)
• timeOffset: The amount of time the subtitles should be offset from the video. (Default: 0)
• onReady: Function that's called when SubtitlesOctopus is ready. (Optional)
• onError: Function called in case of critical error meaning the subtitles wouldn't be shown and you should use an alternative method (for instance it occurs if browser doesn't support web workers). (Optional)
• debug: Whether performance info is printed in the console. (Default: false)

How to build?

Dependencies

• git
• emscripten (Configure the enviroment)
• llvm
• clang
• ragel
• make
• autoconf
• python2
• pkgconfig
• patch
• libtool
• itstool
• automake
• python2-lxml
• python2-pip
• python2-html5lib
• python2-chardet
• gperf

Get the Source

Run git clone --recursive https://github.com/Dador/JavascriptSubtitlesOctopus.git

Build

1. Install Dependencies, see above
2. cd JavascriptSubtitlesOctopus
3. make
4. Artifacts are in /dist

Build with Docker

1. Install Docker
2. docker build -t dador/javascriptsubtitlesoctopus .
3. docker run --rm -v ${PWD}:/code dador/javascriptsubtitlesoctopus:latest
4. Artifacts are in /dist

Why "Octopus"?

How am I an Octopus? Ba da ba da ba!