media-overlays-js

EPUB Media Overlays javascript implementation

This is a partial implementation of EPUB Media Overlays.

See the API for more details

Status:

• jump-to-position doesn't work reliably if you are already beyond the target point
• highlights don't get unhighlighted
• audio sync won't work perfectly when the Chrome tab is in the background. Read more about audio.
• not yet implemented: see future additions

Run test

(first time) Get Ruby 1.9.x, install it, and run:

$ gem install bundler
$ bundle install

Then (every time), start the local server in the source code directory with

$ rake server

Navigate to http://localhost:4000/mo-player.html and press "play"

Future additions

• Skippability
• Escapability
• Audio playback optimization

Approach to SMIL playback

See smil-player.js

Parse a single SMIL file and annotate the XML DOM as follows:

(All nodes) Node.render = function to render that node

(All nodes) Node.notifyChildDone = function called when the node's child is done rendering

(Body and Seq nodes only) Node.playbackIndex = index of the currently-playing child node

The SMIL tree plays itself, calling

root->render

which in turn renders its children.

Media nodes are hooked up to renderers for text display and audio clip playback.

Time container nodes (e.g. seq, par, body) are hooked up to internal renderers to manage playback of their child nodes. For example, seq and body nodes render their children in sequence (often a sequence of pars) whereas par nodes render their children in parallel (e.g. this text with this audio).

When a node is done playing, it must notify its parent via the Node.notifyChildDone method. This method is also used to communicate from the audio clip player to the audio node that owns that clip.