Accessibility/Video a11y Aug09

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Video Accessibility Status Aug 2009 & Nov 2009 & Feb 2010 update

by Silvia Pfeiffer

This is a status report on the progress of video accessibility. I thought I'd publish this snapshot since it is a nice collection of resources around where video accessibility stands right now.

Update Feb 10: The new W3C HTML5 Accessibility Task Force has been founded in Dec 09 and activities for specification improvements and trial implementations are now happening there.

Test File Collection

A collection of time-aligned text files for testing is starting to emerge.

Text files for video/audio in different formats are available from: and

These include:

  • 34 srt files for captions/subtitles in 34 different languages for “Elephants Dream” Blender Foundation movie – these are good for tests of srt support and different charactersets (i18n)
  • 1 srt file and audio recording of audio description in English for “Elephants Dream” – these are good to test audio descriptions for the blind in two different formats
  • 1 srt file for chapter markers for “Elephants Dream” – this tests sectioning and direct access to chapters
  • 1 lrc and 1 qttext file for lyrics for “Chocolate Rain” video and music file CC-licensed by Tay Zonday – this tests different file formats for text annotations and support of accessibility for audio

Further accessibility-related files have been added (Nov 09):

Further accessibility-related files have been added (Feb '10):

Specifications: associating external text

Specifications for how to associate out-of-band time-aligned text with a HTML5 video (and audio) tag as well as how to parse multitrack media files and expose the same attributes, DOM API and JavaScript API are in the making.

Update Nov09:

Update Feb10:

Specifications: JavaScript API for multitrack media

Update Feb10:

Demo implementations using javascript

A collection of JavaScript implementations for associating time-aligned text with audio/video is starting to emerge.

There are demos at - their open source code is available from

The demos consist of the following:

  • "Elephants Dream" with subtitles and captions, chapter markers, and textual audio annotations for screen readers
  • "Elephants Dream" with a different video player skin to test video player controls accessibility
  • "Chocolate Rain" as video with subtitles and as audio with lyrics
  • "Elephants Dream" with a demonstration of how to directly jump to time offsets in videos through URL changes

Update Nov09:

Related open bugs in Mozilla

The following bugs relate to video and audio accessibility at Mozilla:

Related open bugs in W3C HTML WG


Silvia posted the following blog posts relating to video accessibility:

  • “First experiments with itext”

  • “The different aspects of video accessibility”

  • “ARIA – A Brief Introduction”

  • “Updated video accessibility demo”

  • “Open Standards for Sign Languages”

  • “HTML5 audio element accessibility”

New in Nov09:

  • "New proposal for captions and other timed text for HTML5"

  • "Dealing with multi-track video (and audio)"

  • "The model of a time-linear media resource for HTML5"

  • "Manifests for exposing the structure of a Composite Media Resource"

Also the following relate to media fragment addressing, which will enable a deeper interaction with audio and video and thus improve accessibility as well:

  • “Jumping to time offsets in HTML5 video”

  • “Media Fragment addressing into a live stream”

  • “Demo of deep hyperlinking into HTML5 video”

  • “URI fragments vs URI queries for media fragment addressing”

Talks given at:

  • "WebJam 2009 talk on video accessibility"

  • "Web Directions South 2009 talk on HTML5 video"

  • "HTML5 Video element discussions at TPAC meetings"