What is ASF?

A file format is going to spark a revolution? How? Why?

Those questions are answered in "How will ASF spark the multimedia revolution?" To understand the answers, some preliminary groundwork is needed. Let's start by looking closely at ASF.

"ASF" stands for "Advanced Streaming Format." Perhaps the best way to explain ASF is to look at its constituent terms. The term "format" refers to a file format. A file format is a set of rules for arranging, or organizing data. A file format is like the rules for organizing books on a rack of bookstore shelves. Oversize books are stored on the bottom shelf, duplicate copies are stored on the top shelf and laid out horizontally, and the rest of the books are stored in the middle shelves, laid out vertically and ordered by author name. Usually, file formats are thought of in the context of laying data out to disk. But in the "live" Internet world, data can fly around the ether and pop up on your screen without ever touching a disk. This makes no difference to the file format, however. The organization of the data remains the same, whether on disk, in memory, or in network pipes.

The term "streaming" refers to a particular method of "playing" data received over a network. In a network environment, data sitting on a server is sent by the server across the network to a client machine, which then plays the data. The opposite of "streaming" is "downloading." Streaming is to downloading what drinking milk straight out of the carton is to first pouring yourself a glass, and then drinking. Notwithstanding your mom getting a little miffed about it, you knew that drinking from the carton was much more efficient. You didn't have to wait. You could drink more than a glass without missing a beat. There were no dishes to wash. With downloading, the entire data file is received by the client before the client begins to play the data. In the case of data that is a video clip, the entire clip would be downloaded before played. With streaming, the clip is played while it is being received. In other words, as the video clip is being sent across the network and received by the client one piece at a time, the client, on the fly, takes those pieces of the clip and plays them immediately. Streaming is far superior to downloading in that the client does not have to wait for the download to complete in order to begin playing the clip, and the clip does not consume disk space. This opens the door for unlimited-length media, such as live video broadcasts. Even your mom would be happy with you streaming.

The term "advanced" refers to the dynamic nature of the multimedia presentations made possible by ASF. With ASF, a multimedia presentation consisting of video synchronized with PowerPoint® slides that flip at just the right moment, and with ActiveXTM controls that are launched at the right time, can be streamed across a network and played by clients. Actually, ASF allows for the intelligent combination of any and all types of multimedia content, including text, graphics, animation, MIDI, video, and audio, to name a few.

In sum, ASF is a set of rules for describing how multimedia data is organized and laid out on disk. These rules are optimized for streaming the data over a network, and for playing back the data at the client end. Although ASF was developed with an eye toward network streaming, ASF is perfectly suitable for local storage and playback, in light of its optimization for playback. The data stored in the ASF format can represent dynamic, advanced multimedia presentations.

To understand why these ASF rules will spark the digital multimedia revolution, it is first necessary to understand the role that ASF plays in the multimedia world.

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