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Television-like multimedia presentations are coming to the World Wide Web thanks to a new tool developed by the World Wide Web Consortium (W3C) run by MIT's Laboratory for Computer Science (LCS), the National Institute for Research in Computer Science and Control (INRIA) in France and Keio University in Japan.
The Synchronized Multimedia Integration Language (SMIL; pronounced "smile") specification, released as a W3C recommendation on June 15, represents cross-industry agreement on a wide range of features for putting multimedia presentations on the web.
Television programs such as newscasts use many multimedia components. In these programs, the display of image, text and animation elements needs to be synchronized.
The web is already a multimedia environment, but lacks a simple way to express synchronization over time -- for example, "play audio file A in parallel with video file B" or "show image C after audio file A has finished playing." SMIL enables this type of information to be easily expressed, thus allowing TV-like content to be created on the web.
"Synchronized multimedia is becoming increasingly important on the web. The SMIL recommendation will enable much-needed interoperability in this area," said Tim Berners-Lee, W3C director, inventor of the World Wide Web and a principal research scientist at the LCS.
Of course, the web offers far more than just television. For example, a search engine can be used to find a particular SMIL presentation. As the web is inherently interactive, users can use links embedded into a SMIL presentation to obtain background information on a newscast, or to order a product described in a commercial. With SMIL, users can switch from "couch potato" mode into interactive mode with a simple mouse click.
Among its advantages, SMIL is easy to use. Today, few authors write synchronized multimedia presentations for the web because existing approaches require the use of an authoring tool or to learn programming. SMIL removes these roadblocks. It does not require learning a programming language and can be done using a simple text editor.
It also improves bandwidth efficiency. In a typical television news broadcast, large parts of the screen contain text, still images and graphical elements, with full-motion video occupying only a small part of the screen real estate. SMIL reduces the bandwidth of TV-like content, eliminating the need to convert low-bandwidth media types such as text and images into high-bandwidth video.
"SMIL avoids having to swamp the Internet with high-bandwidth video if you want to create interactive multimedia content," said Dr. Berners-Lee.
The advanced multimedia capabilities offered by SMIL give authors full creative control without sacrificing accessibility for web users who have disabilities. In particular, SMIL introduces textual description of multimedia components, provides the capability to support captioning, and supports alternate media types.
"SMIL represents an important breakthrough for accessibility of multimedia," said Judy Brewer, director of W3C's Web Accessibility Initiative International Program Office.
The increasing need for multimedia content and presentation of documents in multiple languages is well met with SMIL. SMIL's internationalization features, including the ability to include multiple audio tracks in a variety of languages, make significant steps towards enabling the proper display of multilingual multimedia documents.
The SMIL 1.0 specification was written and developed by the W3C Synchronized Multimedia (SYMM) Working Group, a mix of experts from four divergent industries: CD-ROM, interactive television, web and audio/video streaming. The W3C SYMM Working Group is comprised of key industry players including Digital, Lucent/Bell Labs, Netscape, Philips, RealNetworks and The Productivity Works, as well as research and government organizations such as the Centre for Mathematics and Computer Science in the Netherlands and the National Institute of Standards and Technology.
A W3C recommendation indicates that a specification is stable, contributes to web interoperability, and has been reviewed by the W3C membership, who favor its adoption by the industry.
A version of this article appeared in MIT Tech Talk on July 15, 1998.