Synchronized Multimedia Integration Language (SMIL, pronounced “smile”) is the Web's answer to SMPTE time code. In the inherently chaotic, nonlinear, non-time-based, low-bandwidth world of the Internet, arranging for the simultaneous display of images with audio has always been a dicey proposition. Numerous plug-in architectures and technologies have been developed by Apple (QuickTime), Macromedia (Flash), and RealNetworks, among others, to accommodate an increasingly multimedia Web, but each involves a closed proprietary format that is completely opaque to inquiry by search engines.
SMIL is the World Wide Web Consortium's (www.w3.org) attempt to standardize multimedia presentation on the Web. SMIL is a subset of Extensible Markup Language (XML), which incorporates meta data into HTML-like tags to encode information into the document itself about its contents and purpose. (For more on XML, see “Web Page” in the March 2001 issue.) A SMIL document looks much like an HTML page in style and structure, but it contains new tags designed to facilitate time-based operations.
For example, the most important tags are and , used to present various media in parallel (such as synchronized audio and video) or in sequence (like a multimedia slide show). The tags can even be nested so that multiple sequential media can be displayed simultaneously. That would let a site show a music video in one window while displaying a sequence of text pages with lyrics and biographical info in another.
There are other tags that perform multimedia functions. The and tags determine placement and style of the various media types in a manner similar to Cascading Style Sheets (a standard format also supported by SMIL). When it is used in conjunction with the tag, the tag can be used to decide which media clip to broadcast, depending on the user's connection speed. For example, high-resolution movies can be streamed automatically to DSL users. Screen size, graphics bit-depth, and other useful information can also be encoded.
The latest version of SMIL was published in June 1998, but implementation of the language into Web browsers has been slow, partly because of competing technologies that already have a large install base. However, Real Networks and Flash support use of SMIL documents in a variety of ways. The system may take on added significance as broadband content becomes more widespread.