Streaming audio

Streaming is a technique that allows you to hear the beginning of some audio or video, while you are still receiving the rest of the information from the Internet, all in one step. This is not quite like 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 it was recorded. If the audio clip was recorded in 42 seconds, then it must be played back in almost exactly 42 seconds, and it must be played at a smooth, constant rate. The technical name for this property of audio is "isochronous," which merely combines the Greek words for "equal" and "time," and is pronounced "i SOCK ron us." Audio and video are the 2 isochronous media. Broadcasting radio or television signals to your home receivers is inherently isochronous, so nobody talks about streaming in those contexts.

The Internet, however, is inherently highly non-isochronous. That is, even if a server places a nice steady stream of audio or video on a nice 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 connection, the information arrives too slowly all of the time, so playing it as it comes in would be unacceptable all of the time.)

Streaming is the technique that waits until some of the information has arrived, and then starts playing what it has received at the correct rate. If everything works out right, you hear the end of the information just after the end of the file arrives. If things go wrong, however, you hear occasional gaps or even repeats, as reception falls behind playing.

If you are interested in playing your audio on the Internet then you should learn how to use RealAudio's streaming audio formats and technologies. (http://www.real.com). The reason is that 85 million people are equipped to play back such audio. Its closest competitor is Apple's QuickTime, which has about 20 million users. Others are Microsoft's Windows Media Technology (WMT), Emblaze Audio, Liquid Audio, and Shockwave Audio. All are available for PowerMac as well as Windows 95, 98, and NT. Note that 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 usually employed to download music for playing later. However, it can also act as a streaming technology for listening to music immediately.

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