As you probably know, HTML5 provides a video tag for rendering a video natively in a web browser (and audio as well). But unfortunately, as of now, HTML5 video isn’t very accessible, yet.
The HTML5 spec has a great plan for captions, timed tracks. It accommodates well for different types of roles (captions, subtitles, descriptions) and multiple languages. The format of the caption text files themselves may be similar to the time stamp format WebSRT (Web Subtitle Resource Tracks). Sadly, there is no support for timed tracks in any browser at this time. The code would go inside the video tag and would look something like this:
About the Codecs/Containers
Not directly related to accessibility, but let’s take a look at the supported video codec/containers of the major browsers. First off, and not surprisingly, Internet Explorer doesn’t support any HTML5 video. And the word is that IE9 will only support WebM if it’s installed on the operating system.
So to cover all major browsers today, you’ll need to encode to an OGG and MP4 file, and then do a Flash video fall-back for IE. Here’s a great table on current support codecs/containers.
It appears WebM will be the codec of the future, but again, it is only partially supported at this time.