Extended audio description via video swap

This demo uses a separate video to deliver audio description. If Description is toggled on, the user gets the described version; otherwise they get the non-described version. Unlike Audio Description Demo #3, the described version uses extended audio description (i.e., the video is paused during description). This results in a described version and non-described version that have different durations. Therefore, any track elements (in this case, captions and chapters) that are intended for the described version must include the data-desc attribute.

For this example:

• The non-described version has English captions and chapters, plus Spanish subtitles.
• The described version only has English captions and chapters, not Spanish subtitles.