Tag Archives: LCA2009

LCA 2009 talk on video accessibility

During the LCA 2009 Multimedia Miniconf, I gave a talk on video accessibility. Videos have been recorded, but haven’t been published yet. But here are the talk slides:

Lca2009 Video A11y

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I basically gave a very brief summary of my analysis of the state of video accessibility online and what should be done. More information can be found on the Mozilla wiki.

The recommendation is to support the most basic and possibly the most widely online used of all subtitle/captioning formats first: srt. This will help us explore how to relate to out-of-band subtitles for a HTML5 video tag – a proposal of which has been made to the WHATWG and is presented in the slides. It will also help us create Ogg files with embedded subtitles – a means of encapsulation has been proposed in the Xiph wiki.

Once we have experience with these, we should move to a richer format that will also allow the creation of other time-aligned text formats, such as ticker text, annotations, karaoke, or lyrics.

Further, there is non-text accessibility data for videos, e.g. sign language recordings or audio annotations. These can also be multiplexed into Ogg through creating secondary video and audio tracks.

Overall, we aim to handle all such accessibility data in a standard way in the Web browser to achieve a uniform experience with text for video and a uniform approach to automating the handling of text for video. The aim is:

  • to have a default styling of time-aligned text categories,
  • to allow styling override of time-aligned through CSS,
  • to allow the author of a Web page with video to serve a multitude of time-aligned text categories and turn on ones of his/her choice,
  • to automatically use the default language and accessibility settings of a Web browser to request appropriate time-aligned text tracks,
  • to allow the consumer of a Web page with video to manually select time-aligned text tracks of his/her choice, and
  • to do all of this in the same way for out-of-band and in-line time-aligned text.

At the moment, none of this is properly implemented. But we are working on a liboggtext library and are furher discussing how to include out-of-band text with the video in the Webpage – e.g. should it go into the Webpage DOM or in a separate browsing context.

If you feel strongly about video a11y, get involved at http://lists.xiph.org/mailman/listinfo/accessibility.