Progress on captions for HTML5 video

Paul Rouget this week published another example implementation for using srt with HTML5 video with a javascript library. This is at least the fourth javascript implementation that I know of for attaching srt subtitles to the video element.

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?

Recently, Greg Millam from Google posted a proposal to WHATWG, that shares a lot of elements with the proposal that has been previously discussed between Mozilla, Xiph, and Opera, the current state of which is summarised in the Mozilla wiki. No implementation into a Browser has been made yet, but initial implementations in javascript exist. I think that we will ultimately come out with a harmonised solution between the browser vendors. It just needs implementation work and continuous improvement.

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. 🙂

ANOTHER UPDATE: My post seemed to imply that Firefox 3.5 will have Ogg Kate support. This is not the case. There is a patch for Firefox and liboggplay to provide Ogg Kate support into Firefox and this patch will be the basis of the Summer of Code project. The student will then work mostly on implementing a comprehensive javascript library to display Ogg Kate encoded time-aligned text (read: captions, Karaoke etc) in the Web browser. This is a proof-of-concept and a first step towards standardising the handling of time-aligned text in Web browsers that suppor the HTML5 video tag.

One thought on “Progress on captions for HTML5 video

Leave a Reply

Your email address will not be published. Required fields are marked *