Magazine article Technology & Learning

Beyond Videodiscs: Compact Discs in the Multimedia Classroom

Magazine article Technology & Learning

Beyond Videodiscs: Compact Discs in the Multimedia Classroom

Article excerpt

Beyond Videodiscs: Compact Discs in the Multimedia Classroom Interative multimedia is the rage in educational technology these days. Most early examples that brought the benefits of multimedia to educators featured the laser videodisk--a 12-inch platter offering access to thousands of still images, up to an hour of video footage, and two parallel soundtracks. No doubt, interactive videodisk applications, which are making their way into classrooms in increasing numbers, will play an important role in education for years to come. But another medium is competing for the attention of those interested in interactive multimedia: the compact disc.

Compact disc technology, popularized by the audio CD in the mid-1980s, offers an advantage over laser videodisc: While the videodisc stores images and sounds in analog form (as do traditional videotapes and audiocassettes), the compact disc is a digital medium). This means that a CD can store computer programs (compact discs used in this manner are known as CD-ROMs), and that the images and information stored on the CD-ROM can be manipulated by the computer in the same way as other digital input. For example, unlike analog images that are sent unaltered from videodisc to monitor, digital images from a CD-ROM can be resized, modified, or combined with images and text from another source before they are displayed on the computer screen. And because of its digital format, data from CD-ROM can be sent via network or modem to a remote computer.

The second major appeal of the compact disc is its capacity. A CD-ROM can store over 600 megabytes of data--the equivalent of hundreds of floppy disks. The presence of all this information on a single disc opens up possibilities for multimedia applications.

As intriguing as the CD is to multimedia developers, it presents some challenges. In particular, there's motion video and the memory it requires. In a digital environment, one of te most straightforward methods of storing a screen image is to save information about the color of each dot ("pixel") on the screen so that the image can be recreated whenever necessary. However, since even a relatively low-resolution image is made up of close to 250,000 pixels and two bytes of memory are required to approximate the color of each one, a single image requires about 500K of memory. One second of "full-screen, full-motion video" (a full-screen video image changing at the speed of 30 frames per second) would require 30 times as much--nearly 20 megabytes. At that rate, an entire CD could hold little more than half a minute of motion video!

Fortunately, the problem is not insurmountable; a number of companies have demonstrated "compression" schemes that greatly reduce the amount of space required for full-motion video. (See box below.) However, it will be some time before such compression routines are perfected, necessary hardware and software tools completed, and a full range of applications that take advantage of compressed video developed. In the meantime, publishers aren't letting the lack of full motion stop them. Instead, they are plunging ahead with CD-based multimedia titles that incorporate text, music, speech, and still images along with limited-screen animation.

What do these applications offer? And what will the machines they run on look like? That depends in part on which audience is targeted. There is a split between those who see the CD as a storage medium for business users looking to extend the computer's capabilities, and those who expect multimedia CDs to be the next consumer electronics craze. Neither camp sees education as its initial market; but both name educational institutions as the second group to benefit from their success. For this reason, it makes sense to watch carefully as the story unfolds.

CD-ROM:

The Computer World's Approach

CD-ROM (Compact Disc-Read Only Memory) has been used as a storage medium for computers since 1984, two years after its relative, the audio CD, was introduced. …

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