On June 15, 1998, the World Wide Web Consortium (WC3) released the Synchronized Multimedia Integration Language Specification 1.0, or SMIL, as a recommendation. SMIL, an XML extension, is intended to allow the easy implementation of sophisticated time-based multimedia content on the Web.
According to the WC3's recommendation, SMIL allows a developer to "describe the temporal behavior of a presentation, describe the layout of the presentation on a screen, and associate hyperlinks with media objects." Because SMIL is a relatively simple declarative language that can be created with a basic text editor, it has the potential for widespread adoption and to have as revolutionary an impact on computer-delivered content creation as HTML. SMIL is supported for Windows in Real Networks' G2 Player, currently in beta release at http://www.real.com, for Windows, UNIX and Macintosh in GriNS from CWI at http://www.cwi.nl/GRiNS/ and for UNIX and Java in HPAS at http://lists.w3.org/. The Website justsmil.com has extensive resources devoted to SMIL.
Capabilities
SMIL allows for the visual layout and synchronization of a variety of media types -- audio, video, graphics and text -- in time-based presentations. SMIL can be used to present a sequence of media files in a timed format like a slide show, or a number of different media types simultaneously for a sophisticated "TV-style" presentation. For example, a .smil file might instruct a player to begin a presentation by playing an audio file, then ten seconds into the audio track, start displaying a timed sequence of JPEG images in the top left corner of the screen. Fifteen seconds later, it could begin rendering a streaming video source while at the same time displaying a series of hyperlinks in the bottom left corner of the screen.
One of the most important features of SMIL is that, like HTML, it allows a presentation such as the example above to be created using distributed media. It is possible for each of the files referenced by a SMIL document to reside on a different server. SMIL does not require a presentation to be "containerized" as proprietary formats such as PowerPoint, Macromedia's Shockwave and Microsoft's Active Streaming Format (ASF) do.
Behind the scenes
The Synchronized Multimedia Working Group of the World Wide Web consortium created the SMIL recommendation. The Working Group is composed of professionals in the hardware, software, digital media and broadcast media industries. The companies represented in the group include Lucent, Apple, Real Networks, Phillips, Bell Labs, DEC, Netscape and CNET among others. According to a paper entitled "Toward Synchronized Multimedia on the Web," published by Philipp Hoschka in the Spring 1997 edition of the World Wide Web Journal, the formation of the Working Group was to combat the "imminent danger that a plethora of non-interoperable solutions for integrating real-time multimedia content into the Web architecture will emerge. These different solutions will most likely not result from a healthy competition advancing technological progress. Instead, they will result from a simple lack of communication between the three very different communities involved, namely the Web community, the CD-ROM community, and the community working on Internet-based audio/video-on-demand."
The earliest efforts of the Working Group revolved around the choice between a declarative format, along the lines of HTML and XML and a scripting format similar to Lingo, JavaScript and HyperCard. Ultimately it was determined that the use of a declarative syntax had many advantages over the use of scripting. Scripting is much harder to maintain and does not lend itself to simple authoring tools.
The advantages of the use of a declarative language becomes apparent during the creation process; sequence changes can be implemented immediately by altering the appropriate descriptor, content changes can be accomplished by replacing a source file with a new one with the same name. In addition, the .smil file can contain meta tags containing keywords and a description of the media contained in the presentation to allow comprehensive indexing by search engines -- something that is not possible with containerized multimedia presentations. The wide variety of tools currently available for converting document processing formats into HTML are a good indication of how easy it will be to create similar tools for SMIL.
The promise of SMIL
SMIL is an important step forward for computer-based multimedia in that it is based on open standards. The world of traditional electronic media -- recording, film and video -- relies on standards to insure that content can be delivered across a broad range of devices and in a wide range of circumstances and conditions. The use of open standards also insures that the content will not become unavailable due to technological obsolescence. It also allows the specification to grow along with technology; new standards can be easily be incorporated as they are introduced. This also insures that legacy content will remain available. The SMIL implementation from Real Networks supports the incorporation of Shockwave, ASF and other containerized content in a SMIL presentation.
In the way that HTML has allowed the traditional methods for creating documents to be extended to a networked environment, SMIL extends the working methods of traditional media to the Internet. At the heart of any film or video presentation is the Edit Decision List, or EDL. Like SMIL, an EDL is a text file in a declarative format that describes the sequence of cuts, transitions, effects and source material used to create the final presentation. EDLs are created in a standard format that can be read by any editing system. This similarity between creating an EDL and creating a SMIL document should make it easy for content creators working in traditional mediums to transfer their knowledge and working methods to the Web. The process of content creation has always been hands-on, and one of the greatest barriers to the Web for traditional content creators -- the need to have knowledge of computer programming or to have access to a programmer -- can be eliminated.
SMIL's ability to create a presentation using distributed media has significant implications for content providers. The first is the ability to reuse media sources. Because SMIL has the ability to display a selected segment of a larger file, multiple presentations can use the same source file. For example, a news site could offer viewers the option to view an entire press conference or just edited highlights using the same streaming video file. The same source file could be used along with simultaneous text or audio translations in a variety of different languages. A provider could syndicate exclusive media content for presentation in a wide variety of customized formats.
The use of distributed media also simplifies bandwidth management. Currently, if versions for multiple bandwidths are required, containerized formats such as Shockwave and ASF require each version to be created from scratch. SMIL, combined with a server enabled for bandwidth detection such as the one from Real Networks, requires only that the source files be encoded at the required data rates; the same SMIL file can be delivered to all viewers. As multi-complexity encoding schemes such as Real Networks' G2 system become widely available, bandwidth management will become even simpler.
The industry-wide involvement and support behind the creation of SMIL bodes well for the standard. The ease of development should open the way for creation of multimedia presentations by those who found the process too difficult or labor intensive up to now. The ability to reuse content and manage bandwidth should prove attractive to sites concerned about the typical overhead involved in delivering multimedia. Development of SMIL implementations is proceeding at a rapid pace. Authoring tools are already available from Real Networks, CWI, Digital Renaissance, and VEON. Additional tools have been announced by a number of other companies.
John Maxwell Hobbs is a musician and has been working with computer multimedia for over fifteen years. He is currently in charge of multimedia development at Ericsson CyberLab New York. His interactive composition "Web Phases" was recently one of the winners of ASCI's Digital '98 competition and is currently on exhibit at the New York Hall of Science. He is also on the board of directors of Vanguard Visions, an organization dedicated to fostering the work of artists experimenting with technology. He is the former Producing Director for The Kitchen. John Maxwell Hobbs can be reached at: john.maxwell.hobbs@ericsson.com.