Module: Broadband Applications


Spring Term — 2008

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Brief: “Design a streaming media presentation using SMIL (Synchronized Multimedia Integration Language). The presentation should be between 10 and 15 minutes long. The streaming media must include the following assets: text, audio, video and flash animation. All these media files should be controlled and synchronized well. Your streaming media should be viewable remotely using RealPlayer or a web browser.”

“What is SMIL exactly?”

Good question… SMIL is an xml-compliant mark-up language that allows multimedia authors to create slide-show style presentations for the Internet – to be played in a browser or on supporting media players. SMIL makes it possible to define the position, timing and layering of different types of media.

I decided that the way forward was to take advantage of the native characteristics of the various media types and the rich SMIL language.  Rather than trying to “squeeze” the elements into a pre-conceived area, I have instead attempted to break up the screen space and take advantage of the timing, positioning and transitioning abilities of the SMIL language.

It would be fair to say that SMIL is not well supported when it comes to Internet browsers or media players – its only saving grace when I did this project was from its implementation on RealPlayer.

This is further complicated by the fact that different browsers and media players do not have universal support of all media types. A SMIL file can refer to any media type, but it will be the browser/media players support (or not) that will determine a) whether it is rendered and b) whether the SMIL file will even be launched.

As an example: a SMIL implementation in HTML for Internet Explorer could reference a video file in the format *.wmv  The file will play because IE supports it.  However, this file will not play in RealPlayer as RealPlayer does not support the *.wmv video format (at the time of this writing).  Another example is *.txt files; SMIL supports *.txt but RealPlayer does not. For a RealPlayer implementation you would have to use RealText (*.rt) files.

Video and disclaimer…

Ironically to upload the SMIL presentation to YouTube I had to convert it to a video format. The result is fairly poor quality… maybe it goes some way to make the point… SMIL is not unified video but synchronized media.

Hopefully you’ll take my word for it, when this is played in RealPlayer the text is sharp and the video and image transitions smooth. At least the video gives an idea of what’s possible as far as animation (yellow bars) and synchronization is concerned.

On the plus side SMIL gives authors the ability to manage and “design” for bandwidth usage – this is its real strength. By keeping individual assets separate and scheduling their delivery, higher quality at lower bit rates is possible.

For example a static image used in your SMIL presentation only has to be downloaded once (and not in a continuous video stream), text which can become unclear in low bandwidth or small screen video can be sent as a separate stream of text and rendered in the clients browser or media player, and will be as clear as text in a word processor. You can also schedule high resolution images and video, buffering them before they are needed.

As an example, here is a screen-shot from the presentation being played in RealPlayer – as you can see the text is sharp and the animation “pixel-perfect”.

If bandwidth is simply not an issue SMIL can be used to swap out different assets depending on your user. It would be fairly straightforward, for instance, to swap your default text for text in a different language. SMILs support of player controls also makes it possible for users to interact with a presentation.

SMIL is a powerful authoring language and will seem familiar to anyone that has used xml or HTML.

However, its proprietary implementation across browsers and media players make authoring for a wide audience problematic. This is not the fault of the SMIL language or W3C which made its first recommendation in 1998. If SMIL were to gain the popularity of say xml then everyone would benefit.


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