Synchronized Multimedia Integration Language (SMIL)

Synchronized Multimedia Integration Language (SMIL) is an XML language. Although content authors can create their own XML languages for such purposes, SMIL is the recommended language for creating multimedia presentations because it includes accessibility and internationalization features. SMIL is supported by two popular user agents for multimedia, RealPlayer and QuickTime Movie Player.

The W3C (http://www.w3.org/TR/SMIL-access/) points out that:

"Dynamic multimedia presents a number of challenges to people with disabilities and to authors of accessible content:

• Authors must provide alternative equivalent content to audio and video so that users with visual or auditory impairments may make use of the presentation. Text content is most valuable to users with a wide range of disabilities, as it may be rendered on the screen, as speech, or on a refreshable braille display. In addition, search engines may process this text content. While there is cost to producing alternative content, the effort may be reduced by using accessible authoring tools (refer to [WAI-AUTOOLS]).
• Alternatives to video and audio content must be synchronized with video and audio tracks. Alternatives that are improperly synchronized may be so confusing as to be unusable.
• A presentation may occupy multiple sensory channels (eyes, ears, and touch) in parallel. Any content, including alternative content, that is presented to a given sense must be coordinated to ensure that it remains intelligible whenrendered with other content meant for that sense.
• The very nature of synchronized multimedia - content changes without user interaction - poses an orientation challenge to some users with blindness, low vision, or cognitive disabilities. These users may still access a presentation as long as the author has provided adequate alternatives and players allow sufficient control over the presentation."

SMIL, considered elsewhere in the AIMS Accessibility Guidelines, provides a way of working on many of the problems of accessibility. Following is a bit of SMIL code from the W3C site at http://www.w3.org/TR/SMIL-access/

<smil>
<p><par><switch>
<!-- audio -->
</switch></par></p>
<p><par><switch>document with SMIL code on the other side - take care!</switch></par></p>
<par><switch><audio alt="My Favorite Movie, Spanish audio"
src="audio-es.rm"
system-overdub-or-caption="overdub"
system-language="es"/> <audio alt="My Favorite Movie, English audio"
src="audio.rm"/> </switch> <video alt="My Favorite Movie" src="video.rm"/>
<textstream alt="Stock ticker" src="stockticker.rt"/> <switch>
<!-- captions or subtitles -->
<textstream alt="English captions for My Favorite Movie"
src="closed-caps.rt"
system-captions="on"/> <textstream alt="Spanish subtitles for My Favorite Movie"
src="subtitles-es.rt"
system-overdub-or-caption="caption"
system-language="es"/> </switch> </par> </smil>
<!--While subtitles only capture dialog in text, captions include dialog as well as text descriptions of off-screen information (e.g., sounds); authors should provide captions when possible. In the switch element, the three textstream elements are rendered in order of preference for Spanish captions, Spanish subtitles, or the default (English) captions. This design allows authors to reuse the captions as subtitles and to ensure that the textstream is not rendered twice when the player is set to support both. -->

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Last updated: 8 March 2002