Ogg has struggled for the last few years to recommend the best format to provide caption and subtitle support for Ogg Theora. The OGM fork had a firm focus on using subtitles in SRT, SSA or VobSub format. However, in Ogg we have always found these too simplistic and wanted a more comprehensive solution. The main aim was to have timed text included into the video stream in a time-aligned fashion. Writ, CMML, and now Kate all do this. And yet, we have still not defined which is the one format that we want everybody to support as the caption/subtitle format.
With Ogg Theora having been chosen by Mozilla as the baseline video codec for Firefox and the HTML5 <video> tag, Mozilla is looking to solve this problem in a community fashion: the solution needs to be acceptable to Xiph, supported by Opera who are also experimenting with Ogg Theora, and ultimately provide a proposal to the W3C and WHATWG that can sensibly be included into HTML5.
As a first step in this direction, Mozilla have contracted me to analyse the situation and propose a way forward.
The contract goes beyond simple captions and subtitles though: it analyses all accessibility requirements for video, which includes audio annotations for the blind, sign language video tracks, and also transcripts, karaoke, and metadata tracks as more generic timed text example tracks. The analysis will thus be about how to enable a framework for creating a timed text track in Ogg and which concrete formats should be supported for each of the required functionalities.
While I can do much of the analysis myself, a decision on how to move forward can only be made with lots of community input. The whole process of this analysis will therefore be an open one with information being collected on the Mozilla Wiki, see https://wiki.mozilla.org/Accessibility/Video_Accessibility .
An open mailing list is also set up at Xiph to create a discussion forum for video accessibility: email@example.com. Join there if you’d like to provide input. I am particularly keen for people with disabilities to join because we need to get it right for them!
I am very excited about this project and feel honoured for being supported to help solve accessibility issues for Ogg and Firefox! Let’s get it right!