2003 Conference Proceedings

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Jared Smith and Peter Blair
WebAIM (Web Accessibility In Mind)
6800 Old Main Hill
Logan, UT 84322
Phone: 435-797-7024
Email: jared@cpd2.usu.edu 
Website: http://www.webaim.org 


Captions are text versions of the spoken word. Captions allow web audio and video to be perceivable to those who do not have access to audio and understandable to a wider audience. Though captioning is primarily intended for those who cannot receive the benefit of audio, it has been found to greatly help those that can hear the audio and those who may not be fluent in the language in which the audio is presented or have learning/cognitive impairments.

The Web Content Accessibility Guidelines 1.0 of the World Wide Web Consortium says, "provide equivalent alternatives to auditory and visual content". Section 508 states that, "Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation." According to these guidelines captions should be:

On the Web, synchronized, equivalent captions should be provided any time audio content is presented. This obviously pertains to the use of audio and video that is played through multimedia players such as Quicktime, RealPlayer, or Windows Media Player, but can also pertain to such technologies as Flash, Shockwave, or Java when audio content is a part of the multimedia presentation.


On the Web, there are three primary technologies for presenting multimedia: Microsoft's Windows Media Player, Real Network's RealPlayer, and Apple's Quicktime. A variety of technologies and standards are used for adding captions to these media players.

SMIL (Synchronized Multimedia Integration Language) is a standards-based language used by Quicktime and RealPlayer to control the layout and presentation of visual and audible items. SMIL is used to control the display, positioning, and timing of captions. The captions themselves are stored in a Text Track file if you're using Quicktime or a RealText file if you're using RealPlayer. Techniques for creating these caption files vary.

SAMI (Synchronized Accessible Media Interchange) is Microsoft's technique for adding captions. A SAMI file is a file that contains the text to be displayed within the captions and information that synchronizes individual caption displays to the multimedia presentation.

Of the three major media players, none yet easily allow real-time captioning. However, tools are in development by WebAIM and others to more easily and cost-effectively allow captioning of live audio and video presentations on the web. Macromedia Flash is also being utilized more than ever to present multimedia content on the Web and strategies are being developed to allow captioning of Flash content.


Fortunately, there are many online resources available to help developers gain an understanding of the technologies and standards used for Web captioning. WebAIM has developed extensive tutorials at http://www.webaim.org/howto/captions/. Developers of the media players also have extensive, though somewhat complicated, resources on how to develop captions for their respective players.


Creating captioned Web multimedia does not have to be a difficult or time-intensive endeavor. There are many tools available to help developers in creating caption files, controlling layout and timing of captions, and getting accessible Web multimedia online. A few popular captioning tools include:

WebAIM is also developing a web-based tool to allow the creation, conversion, and editing of captions for Windows Media, RealPlayer, and Quicktime

References and Relevant Links

Flash - http://www.flash.com 

Hi-Caption - http://www.hisoftware.com/hmcc/index.html 

MAGpie - http://ncam.wgbh.org/webaccess/magpie/ 

Quicktime - http://www.apple.com/quicktime/ 

Quicktime Text Track - http://www.apple.com/quicktime/tools_tips/tutorials/ 

RealPlayer - http://www.real.com/ 

RealText - http://service.real.com/help/library/guides/realtext/realtext.htm 

SAMI - http://www.msdn.microsoft.com/library/

SMIL - http://www.w3.org/AudioVideo/ 

WebAIM - http://www.webaim.org/

Windows Media Player - http://www.windowsmedia.com/mg/home.asp 

Web Accessibility In Mind (WebAIM) is administered through a grant provided by the Fund for the Improvement of Postsecondary Education (FIPSE) Learning Anywhere Anytime Partnerships (LAAP) and Office of Special Education and Rehabilitative Services (OSERS). Our goal is to improve accessibility to online learning opportunities for all people; in particular to improve accessibility for individuals with disabilities who currently may have a difficult time getting access to postsecondary and preschool/K-12 online learning opportunities.

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