videojs-ads

The videojs-ads plugin provides common functionality needed by video advertisement libraries working with video.js. It takes care of a number of concerns for you, reducing the code you have to write for your ad integration.

Getting Started

In addition to the video.js library, you'll need two files from this project: videojs.ads.js and videojs.ads.css. Both are in the src/ directory.

For development, include the CSS in your HTML's <head> section with a <link> tag:

<link rel="stylesheet" href="videojs.ads.css">

Then, include the JavaScript file after video.js, but before your integration code:

<video id="video" src="movie.mp4" controls></video>
<script src="video.js"></script>
<script src="videojs.ads.js"></script>
<script>
videojs('video', {}, function() {
  var player = this;
  player.ads(); // initialize the ad framework
  // your custom ad integration code
});
</script>

With this basic structure in place, you're ready to develop an ad integration.

Developing an Integration

Once you call player.ads() to initialize the plugin, it provides five interaction points (three events and two methods) which you should use in your integration.

Here are the events that communicate information to your integration from the ads plugin:

contentupdate (EVENT) — Fires when a new content video has been assigned to the player, so your integration can update its ad inventory. NOTE: this does not actually fire due to the contentupdate event not firing issue
readyforpreroll (EVENT) — Fires the when a content video is about to play for the first time, so your integration can indicate that it wants to play a preroll.

And here are the interaction points you use to send information to the ads plugin:

adsready (EVENT) — Trigger this event after to signal that your integration is ready to play ads.
ads.startLinearAdMode() (METHOD) — Call this method to signal that your integration is about to play a linear ad.
ads.endLinearAdMode() (METHOD) — Call this method to signal that your integration is finished playing linear ads, ready for content video to resume.

In addition, video.js provides a number of events and APIs that might be useful to you. For example, the ended event signals that the content video has played to completion.

Single Preroll Example

Here's an outline of what a basic ad integration might look like. It only plays a single preroll ad before each content video, but does demonstrate the interaction points offered by the ads plugin.

This is not actually a runnable example, as it needs more information as specified in the code comments.

videojs('video', {}, function() {
  var player = this;
  player.ads(); // initialize the ad framework
  
  var requestAds = function(){
    // fetch ad inventory asynchronously, then ...
    player.trigger('adsready');
  };
  
  if (player.currentSrc()) {
    requestAds();
  }
  player.on('contentupdate', requestAds);
  
  player.on('readyforpreroll', function() {
    player.ads.startLinearAdMode();
    // play your linear ad content
    player.src('http://url/to/your/ad.content');
    player.one('durationchange', function(){
      player.play();
    });
    // when all your linear ads have finished...
    player.one('ended', function() {
      player.ads.endLinearAdMode();
    });
  });
});

Your actual integration will be significantly more complex. To implement midroll ads, you'd want to listen to timeupdate events to monitor the progress of the content video's playback.

For a more involved example that plays both prerolls and midrolls, see the example directory in this project.

State Diagram

To manage communication between your ad integration and the video.js player, the ads plugin goes through a number of states. Here's a state diagram which shows the states of the ads plugin and how it transitions between them:

The timeline at right shows how the ads plugin (labeled "Ads Framework" on the left) communicates with your integration (labeled "Ads Plugin" on the right).

Plugin Options

The ad framework can be configured with custom settings by providing a settings object at initialization:

player.ads({
  timeout: 3000
});

Two options are currently available: timeout and prerollTimeout.

timeout

Type: number Default Value: 5000

The maximum amount of time to wait for an ad implementation to initialize before playback, in milliseconds. If the viewer has requested playback and the ad implementation does not fire adsready before this timeout expires, the content video will begin playback. It's still possible for an ad implementation to play ads after this waiting period has finished but video playback will already be in progress.

Once the ad plugin starts waiting for the adsready event, one of these things will happen:

integration ready within the timeout — this is the best case, preroll(s) will play without the user seeing any content video first.
integration ready, but after timeout has expired — preroll(s) still play, but the user will see a bit of content video.
integration never becomes ready — content video starts playing after timeout.

This timeout is necessary to ensure a good viewer experience in cases where the ad implementation suffers an unexpected or irreparable error and never fires an adsready event. Without this timeout, the ads plugin would wait forever, and neither the content video nor ads would ever play.

If the ad implementation takes a long time to initialize and this timeout is too short, then the content video will beging playing before the first preroll opportunity. This has the jarring effect that the viewer would see a little content before the preroll cuts in.

During development, we found that five seconds seemed to be long enough to accomodate slow initialization in most cases, but still short enough that failures to initialize didn't look like failures of the player or content video.

prerollTimeout

Type: number Default Value: 100

The maximum amount of time to wait for an ad implementation to initiate a preroll, in milliseconds. If readyforpreroll has been fired and the ad implementation does not call startLinearAdMode() before prerollTimeout expires, the content video will begin playback. prerollTimeout is cumulative with the standard timeout parameter.

Once the ad plugin fires readyforpreroll, one of these things will happen:

startLinearAdMode() called within the timeout — preroll(s) will play without the user seeing any content video first.
startLinearAdMode() is never called — content video plays without preroll(s).
startLinearAdMode() is called, but after the prerollTimeout expried — bad user experience; content video plays a bit, then preroll(s) cut in.

The prerollTimout should be as short as possible so that the viewer does not have to wait unnecessarily if no preroll is scheduled for a video. Make this longer if your ad integration needs a long time to decide whether it has preroll inventory to play or not. Ideally, your ad integration should already know if it wants to play a preroll before the readyforpreroll event.

Building

You can use the videojs.ads.js file as it is in the src/ directory, or you can use a minified version.

The ads plugin is designed to be built with npm and grunt.

If you don't already have npm, then download and install Node.js (which comes with npm). Then you can install the build tool grunt:

$ npm install -g grunt

With grunt ready, you can download the ads plugin's build-time dependencies and then build the ads plugin. Open a terminal to the directory where you've cloned this repository, then:

$ npm install
$ grunt

grunt will run a suite of unit tests and code formatting checks, then create a dist/ directory. Inside you'll find the minified ads plugin file videojs-ads.min.js.

Release History

A short list of features, fixes and changes for each release.

v0.1.0

Initial release.

License

See LICENSE-APACHE2.

GLStephen/videojs-ads