What Is Streaming Audio?

Streaming audio is similar to traditional radio broadcasting except that the Internet is used to send and receive audio instead of using the airwaves. Just like turning on the radio, streaming audio is listened to in real time. This is much more convenient than the two-step process of listening to an audio file after a (frequently time-consuming) download is complete.

Several components are involved in listening to streaming audio. It starts with a connection to the Internet (via dial-up modem, DSL/ISDN, LAN, and so on) and a Web browser such as Netscape or Internet Explorer. Using the browser on a home computer, the user visits a Web site that offers audio of some kind or another. It may be music, or spoken word...anything that makes noise. When clicking on a link to that content, a player application starts playing automatically.

What really happens here is that the player application connects to a streaming server and requests the chosen streaming audio content. The streaming server takes the streaming audio from either a static preprocessed file or a continuous live feed (such as an ongoing Internet "radio" station) and begins sending the audio over the Internet connection to the user. After a brief buffering process, the audio is played through the user's speakers as it is received. (Buffering is performed to avoid excessive dropouts, and is similar to the feature on most portable CD players that prevents dropouts from jarring vibrations.)

As shown in Figure 1.1, streaming audio is delivered to the user's computer over an Internet connection, typically a telephone or cable line. The technology that makes streaming audio work is primarily about squeezing the original audio file down to as small a size as possible and still reach the user in some semblance of sonic legibility. Standard dialup telephone modems can only handle a limited amount of information that's why streaming audio, to the ears of careful listeners, is often defined by its limitations. Most streaming audio does not sound like the original audio file. It has been compressed (squashed) and had portions of its original frequency spectrum removed. But remember: We're not talking about audiophile-quality sound here. We're talking about usefulness. Streaming audio is an extremely useful technology. By the time you are finished with this book, you should be able to see that for yourself.

Figure 1.1. Audio pathway from live-encoding station through the Internet, to server through the Internet, and to home PC and player/speakers.

What Is the Difference Between Download and Streaming?

Unlike downloaded audio, streaming audio is heard as it is delivered to the user. When downloading audio content from the Internet at slower modem speeds, it's often necessary to wait as long as 30 minutes or more to hear one three-minute song. The familiar analogy for streaming audio is that it's like turning on your radio: You hear it immediately, in real-time. On the other hand, downloadable audio is like going to a store, buying a CD, and listening to it only after you have returned home.

A (Very) Brief History

Streaming audio is still a very young technology. Consider that the home computer has only been around a few years longer than the CD format. In terms of what the next few years has in store, you wouldn't be too far-out to consider the current state of streaming audio as the technical equivalent of vacuum tubes. A brief chronology follows:

• Prior to 1991 The Sun-AU format (also called Ulaw) is the downloadable audio standard. It's small (8 bit), available in mono only, and sounds like a really bad telephone connection. A handful of people have excruciatingly slow dial-up connections (2400 baud).

• 1993 AIFF and WAV formats become commonly used for downloadable audio. The formats can sound great when not super-compressed, but files are too large and take too long to download. The average home dial-up rate increases to 14.4k baud and the World Wide Web arrives in our collective consciousness.

• 1994 A digital media compression scheme called MPEG (for Motion Picture Experts Group) piggybacks the Web's dramatic increase in use. The scalable audio portion of MPEG technology offers much smaller files, which enables much faster download times and better sound quality. Individuals and corporations make players and encoders to support online audio's growing popularity.

• 1995 Streaming audio enters the scene. High profile companies such as Progressive Networks (later to be renamed RealNetworks) with their RealAudio product and Xing Technologies' Streamworks product make the streaming audio easily available to all, although still at poor quality. Web users no longer have to wait for an audio file to download before listening.

• 1996 RealNetworks and Xing begin to continually trot out new versions of their software. Macromedia's Shockwave Audio is released, allowing MPEG 1, Layer III (MP3) technology to be embedded into Web pages. The big players, including Microsoft and Apple, recognize the value of this rapidly expanding market. Everyone works feverishly to stay ahead of the pack, hoping to become the one standard for streaming audio. Smaller companies are buried or gobbled up in the increasingly aggressive fight for market share. Within months, millions of people are online. Launched later in the year, Liquid Audio, a distribution system, includes superior quality audio based on Dolby Labs AC3 technology. The hype about Internet audio peaks, and major corporations throw big money into securing market share.

• 1997 RealNetworks expands its focus to include video. Microsoft launches NetShow (soon to become Windows Media).

• 1998 The popular use of the MP3 format shakes the roots of the music business. Users begin to have access to fast connectivity via DSL and cable-modems, allowing for streaming of ever-higher quality audio. Internet radio arrives.

• 1999 MP3's popularity and low price make it the most popular downloadable audio format. MP3 also offers some competition in the streaming audio arena. Portable MP3 players, such as the Rio, become available. Streaming audio formats that survive the first five years RealMedia, Windows Media, and QuickTime launch more aggressive marketing campaigns. Nullsoft, creators of the popular Windows-based MP3 player, Winamp, launches SHOUTcast, a simple and stable MP3-based streaming audio system.

• 2000 2001 Web sites such as www.live365.com offer to handle individuals' streaming for free and large streaming service providers Akamai, Digital Island, and Speedera expand their services for corporate clients. The Internet hype bubble bursts but, thankfully, innovation continues.

Streaming Audio Uses

Streaming audio has become commonplace for a variety of commercial and non-commercial uses. From traditional (streaming a terrestrial FM radio station) to esoteric (streaming audio files of the sound of gamma rays hitting Earth's atmosphere), the technology has inspired millions of people to make their own online audio statement. A quick list of uses includes the examples mentioned previously, as well as private family Web sites, music or band promotion, public sector information, corporate marketing, emergency services dispatch, language and pronunciation tutorials, and live concerts. You can even listen to conversations with Tibetan llamas recorded in stone huts at high altitude. There's no limit to what the fertile mind can do.