YouTube, Vimeo and DailyMotion video sites have recently started rolling out implementations of HTML5 Video. Noting that they do not have captions, I was asked to write a little about what is going on.
Synopsis: HTML5 is not a standard, it is still experimental, and as such, all standards have not been agreed upon. Captions can be done, of course, but since no standard is determined yet for displaying video, there are no finalized standards for captions. YouTube, Vimeo, and DailyMotion are websites that are testing the tags and taking sides, and Google, Safari, Mozilla, and Opera are the browsers taking on the tags, and choosing sides. (Microsoft is late to the party. <cite>http://news.cnet.com/8301-1001_3-10305822-92.html</cite>).
Okay, now you know the basis, if you are curious about more, read on.
Most everybody has heard of HTML (Hyper Text Transfer Protocol), but most don’t really understand what HTML is. I like the way <cite>http://www.yourhtmlsource.com/starthere/whatishtml.html</cite> describes it:
<blockquote>
The definition of HTML is HyperText Markup Language.
- HyperText is the method by which you move around on the web — by clicking on special text called hyperlinks which bring you to the next page. The fact that it ishyper just means it is not linear — i.e. you can go to any place on the Internet whenever you want by clicking on links — there is no set order to do things in.
- Markup is what HTML tags do to the text inside them. They mark it as a certain type of text (italicised text, for example).
- HTML is a Language, as it has code-words and syntax like any other language.
</blockquote>
There are many versions of it, you can read about them <cite>http://www.yourhtmlsource.com/starthere/historyofhtml.html</cite>, but the main point is that the versions currently in use (4.01, xhtml 1.0) were developed in 1997 and 2000, respectively. HTML5 is a standard that is still in draft form <cite>http://www.whatwg.org/specs/web-apps/current-work/multipage/</cite>.
Video is one of the things that is still being argued and decided on, the intent being to make video work on the browser instead of with “plug-ins” (added software to the browser). There is currently not an agreed upon standard for displaying this format, but web browsers and websites are starting to implement this standard before the standard is complete. <cite>http://shaver.off.net/diary/2010/01/23/html5-video-and-codecs/</cite>. In short, Mozilla wants to use an open standard, with no licensing fee, and Google wants to use h264, with license fees and heavy patent enforcement.
Since the standard for how to display the video is not defined, it is natural that how to display captions is not defined. There is a standard format, DFXP (Distribution Format Exchange Profile)<cite>http://www.w3.org/TR/ttaf1-dfxp/</cite> that is in progress, hoping to include a full range of capabilities <cite>https://wiki.mozilla.org/Accessibility/Video_a11y_Study08</cite>.
There are several examples of how captions *can* be implemented with javascript, but not standard format. <cite>http://blog.gingertech.net/2008/12/12/attaching-subtitles-to-html5-video/</cite>, and my favorite implementation so far (Firefox 3.1+/ogg) – http://www.mozbox.org/pub/srt/index2.xhtml
This is where my understanding is at, let me know if you have any questions.
billcreswell.words 
Note that while I do believe this is experimental, Google will probably change to use the On2 technology, and the Google will probably be adding those features back in, it doesn’t hurt to remind them of the importance of the captions and audio track features!
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