Get up to speed with SMIL 2.0

SMIL 2.0, the Synchronized Multimedia Integration Language, has begun to establish itself as an important new approach for integrating multimedia into Web content. SMIL, which offers XML-based approaches for controlling the timing and presentation of multimedia elements, has begun to attract the support of many large software vendors and toolmakers, making it increasingly accessible for developers. In this article, Anne Zieger provides an overview of SMIL and describes several tools available to make SMIL coding simpler.

For developers outside the multimedia world, the Synchronized Multimedia Integration Language, or SMIL, may be something of an obscure technology. But at least among a few key players, SMIL has begun to establish itself as an important approach to presenting multimedia online.

SMIL support has crept into technologies backed by Adobe, Microsoft, and perhaps most prominently, media delivery leader Real Networks. A wide variety of smaller vendors have begun to provide SMIL authoring tools and players as well.

In days to come, as support for the current 2.0 specification grows, working with SMIL could become a standard strategy for any developer whose work requires some form of multimedia asset control. If the growing roster of tool creators is any indication, building presentations in SMIL should become easier as well.

SMIL history and overview

SMIL has been in development since March 1997, when the World Wide Web Consortium (W3C) established a working group on synchronized multimedia.

SMIL is an XML-based language that allows authors to write interactive multimedia presentations without using multimedia management tools such as Macromedia Director. Authors can describe the timing of multimedia presentations, associate hyperlinks with media objects and define the layout of the presentation onscreen. The SMIL 2.0 spec, for its part, is a series of markup modules defining semantics and XML syntax for certain SMIL functions.

The W3C released the first version of SMIL in November 1997, attracting a moderate level of industry attention, including some support from Real, Adobe, and Microsoft.

With the 2.0 version of SMIL, released in August 2001, these companies remain on board; in addition, more than a dozen independently-crafted SMIL authoring platforms have arrived on the market. According to W3C documents, SMIL 2.0 has two main design goals:

1. To further define an XML-based language that allows authors to write interactive multimedia presentations.
2. To allow re-use of SMIL 2.0 syntax and semantics in other XML-based languages, notably integrating timing into XHTML and Scalable Vector Graphics (SVG). (SVG is a language for describing two-dimensional graphics in XML.)

One example of how the group met the second goal is Microsoft’s XHTML + SMIL profile, which integrates SMIL directly with XHTML and Cascading Style Sheets. While technically not part of W3C’s SMIL 2.0 recommendation, they’re linked; one of the implementations used to validate SMIL 2.0 was based on the XHTML + SMIL profile.

Vendor support

Arguably, the most dedicated and visible vendor in the SMIL arena is Real Networks, whose RealOne player supports playback of SMIL presentations. To support SMIL authoring, Real released its own XML/SMIL authoring tool, SMILGen, in September 2001.

Microsoft added a subset of SMIL support to Internet Explorer starting with version 5.0. The current version of IE, 6.0, has extended its SMIL support. IE 6.0 allows developers to:

• Use SMIL filters and effects (such as fading an image)
• Transition between text or media elements by using wipes
• Apply a graduated color background to an element, controlling the timing for each

Another SMIL-friendly vendor is Adobe, whose visual authoring program for Web designers, GoLive Studio, offers both SMIL and QuickTime editors. GoLive is designed to be a highly comprehensive package; the fact that SMIL is included as a standard feature suggests the extent to which it has become an accepted approach to media production.

The wireless industry, meanwhile, has taken on SMIL as a means of enriching its current text-based messaging technology. Many industry players expect to see the highly popular Short Messaging Service (SMS) evolve into Multimedia Messaging Service (MMS) as wireless networks adopt second- and third-generation technologies. Using SMIL encoding and SMIL-based players, MMS would add text, images, audio, and eventually video to SMS.

Read more of this article at IBM