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Is compressed video ready for school?

Basic rate ISDN proved itself in a distance learning application in California, but the quality of its compressed images may not be good enough for the video sophisticates that now occupy the nation's classrooms.

Those were the conclusions of Terry Curtis, whose Department of Communication Design at California State University at Chico ran a two-week distance learning test last year and another this spring.

Curtis detailed his experiences in a presentation to the spring Broadband ComForum, sponsored by the National Engineering Consortium. He brought an interesting perspective to the table, being far more concerned with educational quality than with how Point A and Point B are connected.

"The issue is not to define the transmission medium, the issue is to define the learning objective," Curtis says.

"You have to know the style, the communication capacity and skills of the instructor. You have to know who the students are, what they already know and their learning styles. You have to know the nature of the message, its information intensiveness, and the learning objective.

"Once you know all those things, then you can figure out what kind of channel you need. Until you know all those things you are going about it the wrong way if you start with the channel and work back.

"We told AT&T and Pacific Bell (the university's test partners) that it was the wrong way around, but it was an interesting project nonetheless and somebody's got to figure out what limits there are on the usefulness of basic rate ISDN."

Cal State Chico and Fairview High School share a Pac Bell central office, so the university was a logical choice for the test. It consisted of the Fairview High science teacher doing four two-hour teaching segments from the university campus.

The teacher wanted full duplex audio so he could hear his students and they could hear him, but interactive video wasn't crucial.

"He didn't see the two-way interactive video as necessary. He wasn't sure what his students looking at him would do for the lesson. He was a little more interested in being able to look at his students, but what he really wanted was the ability to show his students videos and animations prepared ahead of time."

For the test, Curtis and the teacher used off-the-shelf components, among them a 386 workstation with VGA graphics, Compression Labs Rembrandt II codec, Panasonic laser disk player, video camera, scanner, conference microphone and graphics tablet.

There were two basic rate lines--four B channels--involved. Two were dedicated to 128 kb/s video. The teacher could see his students and they could see him.

On the other basic rate line, one B channel was used as an off-line voice channel so the teacher could talk privately to a remote teacher's aide or to individual students.

The fourth B channel was used for graphics stored on hard disks in both sites. It controlled a videodisc player that showed the students video and animation that the teacher and Cal State Chico students had prepared.

"We took all that video and had it mastered into a couple of disks for about $1,000. There were two copies of the same disk at either site so that the full motion video the teacher wanted was being seen simultaneously at both sites, but not being transmitted," explains Curtis.

As far as the ISDN itself goes, "it works, it's flexible, it's reliable," Curtis says. A second, later test involved a prototype ISDN multimedia bridge that connected three elementary schools in a setup that shared a single science teacher.

Curtis says the test demonstrated that compressed video is not adequate for a generation of students who have grown up with broadcast quality images.

"High school students and even college students are very uncomfortable with compressed video. The students in our test were tolerant of the poor quality of video because what they were seeing was their teacher.

"They didn't need to see his expressions. They could guess them from his tone of voice. The information intensity in familiar faces is zip. If, on the other hand, you need to get someone's expression or you have unfamiliar faces, then you have to have better resolution. You can't see that over highly compressed video.

"Two-way full-motion video with low-intensity information is wasteful. But if you have very information-intensive instructional objectives, then anything less than two-way full-motion video is inadequate."

ISDN may still be there to provide this full-motion video, but it will have to be the broadband version to suit educators and students.
COPYRIGHT 1992 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:ISDN Forum; integrated services digital network
Author:Tanzillo, Kevin
Publication:Communications News
Date:Jun 1, 1992
Words:754
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