It is great to see such a huge need for this. At the same time I am also worried about the amount of incompatible implementations of this feature. It will inhibit search engines from realising which text relates to and describes a particular video. It will also inhibit accessibility technology such as screen readers or braille devices from realising there is text that would be necessary to be rendered.
A standard means of associating srt (or other format) subtitle files with the video tag is really necessary. So, where are we at with this?
At the same time, in-band captions that come multiplexed within the Ogg file are also being progressed. At Xiph we are now focusing on using Ogg Kate for these purposes – it really don’t make much sense to invent another codec when Ogg Kate is already so close to solving most problems. So, between the developer of Ogg Kate and myself, we are preparing a Google Summer of Code project that should see a implementation for Firefox 3.1 that is capable of extracting the text from an Ogg file that has a Kate track and displaying that track as though it was a srt file. If you are interested, shoot me an email!
UPDATE: Firefox 3.1 is apparently now called Firefox 3.5 – sorry guys. 🙂