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Getting Ready for Audio on the Web

© Anne Kellerman

We are starting to see more and more audio as part of multimedia Web pages.Where are some a state-of-the-art tools to create streaming audio. To start learning about audio to position yourself to use these tools, you should make sure you can use your operating system's sound recording accessory (or something fancier) to record and play back a simple .wav file (or the Mac equivalent). This is digital audio, but it is not streaming audio.

To play a .wav file that is associated with a Web page on the Internet, you need to first download the entire file. This may take quite a while, particularly if the file is large and the net is slow. Moreover, the wait is unpleasant because you have nothing to listen to until the download to complete. Then you play the file that you downloaded.

Streaming is a technique that allows you to hear audio or video while you are receiving the information from the Internet, all in one step. This is not quite as trivial as listening to a radio or TV broadcast as you receive the signal from the station that sends it, for a rather important technical reason. An audio clip must be played back in a time that is equal to the time in which the was recorded. The technical name for this property of audio is "isochronous," which merely combines the Greek words for "equal" and "time." Video is the other isochronous medium. Broadcasting of radio or television signals to your home receivers is inherently isochronous, so nobody talks about streaming in those contexts. However, the Internet is inherently non-isochronous. That is, even if a server places a nice steady stream of audio or video on a fast Internet connection, what you get off the Internet is likely to come too fast for a while, then too slow, then too fast again, and so on. Listening to the information as it comes from the network would be unacceptable most of the time. (Of course, if you are receiving video or high quality audio over a slow network, the information arrives too slowly all of the time, so playing it would be unacceptable all of the time.) Streaming is the technique that waits until some of the information has arrived, and then starts playing at exactly the desired rate, based on timing information that the server added to the audio or video information.

There are several streaming audio formats and technologies. They go by names such as Emblaze Audio, Liquid Audio, QuickTime, Shockwave Audio, and Real Audio. All are available for PowerMac as well as Windows 95, 98, and NT. We will show you how use RealAudio because it is the one that the largest number of people are equipped to receive in streaming mode. Even more people have the ability to receive QuickTime, for example, but only in non-streaming mode. Similarly, the Internet audio format that is now getting most notoriety in the popular press, known as MPEG-1 Level-3, or MP3 to its friends, is not a streaming technology.