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Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

What is webcasting? To see a real working example, point your Web browser at eWeek's webcast site ( You can choose from a list of news items and hear streaming audio and video presentations. A player is required, either RealPlayer from RealNetworks or Microsoft's Windows Media Player. Depending on the bandwidth available, you may see an actual moving image, rather than a series of changing still images. The audio is usually pretty good, though, and certainly beats reading text on the screen, and live interviews give you the emotion of the person speaking.

The technology behind webcasting is streaming audio and video. That means RTP (Real-time Transport Protocol) over UDP (User Datagram Protocol) in most cases. These technologies are outlined under "Multimedia" along with related technologies.

Webcasting is also called "netcasting," "Internet broadcasting," or "data broadcasting," although webcasting is more associated with streaming video and audio. Data broadcasting is more about sending news, stock quotes, and related information to subscribers using "push" techniques. Push is the opposite of "pull," which is what you do when you access Web site. With push, Web sites automatically send you information. E-mail is a push techniques that people use to send other people information, sometimes without the recipient asking for it. Think of push in terms of low-bandwidth data broadcasting (stocks, news, sports headlines). Think of webcasting as full multimedia broadcasting.

The ultimate webcasting technology is multicasting, which is based on special Internet protocols that deliver content along efficient paths from the sender to multiple receivers. The idea is to send packets only along paths that lead to subscribers of the multicast information, thus cutting down on traffic. See "Multicasting."

The webcasting community even has its own organization called the International Webcasting Association. Its Web site is listed on the related entries page. The IWA serves companies that are active in the delivery of multimedia (audio and video) services to consumers or business customers via the Net and other networks. Another association is DiMA (Digital Media Association).

One thing to keep in mind is the U.S. government's Digital Millennium Copyright Act. Special provisions were added for webcasting in 1998 that cover licensing of Internet radio stations, which is essentially audio webcasting. A good source for legal information on this type of webcasting is a set of articles by Sean Flinn at ZDNet Music. The Web site is listed on the related entries page.

Microsoft has done a lot of work to integrate webcasting into its Windows product line. It defines webcasting as a generic term that refers to any automated delivery of personalized and up-to-date information. Webcasting is made possible through the Windows Active Desktop and Active Channels. The Active Desktop provides a common and customizable user interface for organizing webcast sites and information. A typical Active Desktop might contain a weather chart that is updated constantly. Users subscribe to sites that support Active Desktop. Subscription and updates may be handled by CDF (Channel Definition Format), which provides a format that publishers can use to define elements such as media channels, types of information, schedules, and so on. This information helps users subscribe to and manage content.

Webcasting Sites and Services

One of the best examples of webcasting is Yahoo! Broadcast. Yahoo! purchased to acquire the webcasting technology. The site can be accessed at It is described as a place where businesses and content providers can deliver corporate communications messages via audio and video streaming. Applications include product launches, press conferences, e-learning, seminars, keynote addresses, annual shareholder meetings, quarterly earnings calls and corporate TV channels. Services include the following:

  • Webcasting services such as live and on-demand audio and video broadcasting, pay-per-view broadcasting, secured broadcasting, and multicasting services

  • A/V production services, such as live webcast engineering, audio/video production, and satellite connections

  • Web and multimedia development, such as synchronized multimedia and front-end interface development (registration, polling, surveying, testing)

NetTalk Live is another webcasting company that combines webcasts with live events on television or radio. It refers to this simultaneous broadcasting as triplecast. Viewers watch programs on TV while using their Web browser to interact with the program.

Still another webcasting provider is CNET Networks' (simply type in your Web browser). The CNET site provides previews and cuts from movie and television shows, as well as its own webcasts.

Content distribution providers such as Akamai, Inktomi and Digital Island provide streaming services that enable Internet content providers and enterprises to host webcasts on their distributed caching networks worldwide. Akamai's network consists of caching servers located at service providers sites around the world. These sites host content "close" to users, which avoids running lengthy multimedia presentations over multiple hops on the Internet.

Microsoft is one of the best sources of information about webcasting technologies. Go to to view extensive information about media content creation tools, editing tools, and services. Another good source of information is For additional information about streaming multimedia, see "Multimedia."

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
All rights reserved under Pan American and International copyright conventions.