Streaming Media

by Tim Dereg

In this article:

The Future

SMIL (Synchronized Multimedia Integration Language) is a new markup language being developed by the World Wide Web Consortium (W3C). Once fully implemented, SMIL will enable Web developers to divide multimedia content into separate files and streams (audio, video, text, and images), send them to a client's computer individually, and then have them displayed together as if they were a single multimedia stream.

The ability to separate out the static text and images should make the multimedia content much smaller so that it doesn't take as long to travel over the Internet. SMIL is based on the eXtensible Markup Language (XML). Rather than defining the actual formats used to represent multimedia data, it defines the commands that specify whether the various multimedia components should be played together or in sequence.

Summary

• Streaming media is a method for delivering multimedia content, where video, audio, graphics, and animation can all play simultaneous roles in the presentation.
• You can start viewing a streaming media presentation almost immediately while the file itself is still being sent from the server; there is no waiting period while the component files are first downloaded to your computer's hard drive.
• Current network architecture cannot process the quantity of real-time data required to render it into a full-screen, television-style presentation on your computer monitor. In addition, any file being streamed to your monitor must be transferred at a rate that your modem can handle. This slow data rate means that the streaming media can be displayed only in a small window if it is to be displayed in anything close to realtime.
• The component files in a multimedia presentation are compressed through the use of codecs (compressor/decompressors), which are basically mathematical formulas, or algorithms, that reduce the amount of data within each frame. The most widely used codecs reduce file sizes by discarding data. This technique is termed lossy compression.
• A video that has only a small amount of change from frame to frame, such as a 'talking head shot' against an unmoving background, can be compressed to a much smaller size than, say, a video of a parade where constant movement fills each frame.
• The most commonly used compression formats are AVI, QuickTime, and the MPEG family of standards.
• Compression types are divided into lossless and lossy.
• When shooting a video that will be streamed, keep movement to a minimum and fill the frame with your subject.
• People are more sensitive to degradation of audio than they are to video; if the audio is harsh and garbled, your users are less likely to be satisfied with your media. If you start with high-quality audio, you can still compress it using some of the more extreme settings and still have acceptable results.
• Low bandwidth (such as a 28.8 Kbps modem) is not suitable for content with a lot of motion in it, such as a sports event. Video interviews with individual sports stars, on the other hand, would give perfectly acceptable quality over a 28.8-Kbps connection.
• For your content to fit within a given amount of bandwidth, you need to balance the following factors: frame size, frame rate, video quality, and the number of colors available for display.

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