SMIL in interactive audiovisual presentations
The Synchronized Multimedia Integration Language (SMIL, pronounced “smile”) enables simple authoring of interactive audiovisual presentations. SMIL is typically used for multimedia presentations that can integrate streaming audio and video with images, text or any other media type.
SMIL presentations are described by text files. You can create or edit a SMIL presentation using a text editor, and you can automatically generate a SMIL document using any script language that creates text files. A SMIL document specifies what media elements to present and where and when to present them.
Media elements in a SMIL document are specified by URLs. Media elements can be files such as text files, JPEG images, QuickTime movies or live streams. The URLs that specify the media elements can use any of the common protocols: HTTP, FTP, RTSP, file access and so on.
Your SMIL presentation can use any media elements that QuickTime can play, including still images, audio, text, QuickTime movies, sprite animations, live streams, VR panoramas and VR object movies.
Because SMIL documents are text files, SMIL also gives you a way to automatically generate customized QuickTime movies using a script, such as an AppleScript, PERL or CGI script - anything that can generate text output can create a SMIL document. If you have a script that inserts banner ads into your web pages, for example, you could use the same script to insert the ads into a SMIL document along with a streaming QuickTime movie.
Like the tracks in a QuickTime movie, the media elements in a SMIL presentation can be sequenced, overlapped or offset in time and space.
SMIL Structure
SMIL is based on XML, so it is more rigidly structured that HTML, but it uses the same familiar <tag> and </tag> syntax.
SMIL is different from HTML in that all the tags are case sensitive (always lowercase) and all tags have to be explicitly ended either there are a pair of tags that enclose other elements (<tag> elements </tag>) or a tag is self contained and ends with ” />” (<tag parameters />).
SMIL also differs from HTML because HTML routinely mixes structure and content together in the same document, whereas SMIL normally does not. Where an HTML document contains text to be displayed, a SMIL document would contain the URL of a text file instead.
Like HTML, a SMIL document has a head and a body. The structure of a SMIL file is shown below.
<smil>
<head>
<layout>
<!– layout tags –>
</layout>
</head>
<body>
<!– body tags –>
</body>
</smil>
source : http://www.apple.com/quicktime/technologies/interactivity/smil.html
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