With systems of varying quality costing from $250 to more than $10,000, almost any budget can afford to give videoconferencing technology a try
By Stephen Lawton
After years of hype and false starts, videoconferencing is turning into a viable application. Network speeds are increasing, and bandwidth is becoming more controllable in the WAN. But with prices ranging from $250 to more than $10,000, the differences between high-end and low-end systems, as well as LAN-based and dial-up systems, are becoming more pronounced.
LAN environments offer two locations for videoconferencing. In a conference room, cameras and microphones are used and connected to other sites. At the desktop, each user sits in front of a camera and multimedia PC.
For a system that offers TV-quality voice and video at the desktop, network managers should be prepared to spend $2,000 or more. But a clear picture when the person seen onscreen is stationary does not guarantee TV-quality moving images. Experienced videoconferencing participants will testify that movement is generally not recommended.
Macroblock sampling, popular in many products, uses an averaging approach to displaying colors and objects, and movement could put a portion of the picture out of focus, says Nancy Miracle, CTO of Intelect Visual Communications Corp. in New York. She described the moving video image as "cubist," meaning boxes of blurred color appear until the next video refresh.
Intelect takes a different approach and uses wavelet video technology, which provides for frame-by-frame compression. This technology considers what the human eye can see and compresses data on a sliding scale--more where the eye discerns less, and less toward the edges of visible light. As a result, images appear better focused, even when one of the images in the picture moves, according to Miracle.
But images displayed on a computer screen are sometimes insufficient. When several people participate in a videoconference from a large meeting room, a projector-based system such as the Polycom Inc. ShowStation IP can be deployed. Combine this with telephony systems that include omnidirectional microphones placed throughout the room, and several attendees can participate from a single site. Projector-based systems can cost more than $10,000.
The camera in such environments used to be fixed, so it was difficult to get a clear image of the participants, says Brian Hinman, president and CEO of San Jose, Calif.-based Polycom. But this no longer presents a problem. A camera that detects the speaker and adjusts to focus on that person is now available.
Other solutions for group conferencing include PictureTel Corp.'s Socrates system, a podium-based unit that lets the presenter change images and move cameras with a touchscreen. This gives one member of the conference greater control over its direction.
However, videoconferencing still faces limitations. For instance, no end-to-end Quality of Service exists for video images over Ethernet.
Another problem is IP multicast technology. There is no guarantee of service, and it's impossible to determine when a session begins or stops. These issues are based on videoconferencing's underlying technology: Ethernet and IP.
One differentiator between LAN-based and dial-up videoconferencing is the number of participants that may be seen. Many dial-up products are simply point-to-point. LAN-based products have the capability of accessing multiple phone lines over the Internet with a gateway and IP telephony software or through a PBX.
Dial-up users are limited to a single connection with one phone line. The image is often sent through a small camera connected to a parallel port, and the sound is handled through a built-in or external speaker.
Japan Computer and Communications Inc. (JCI) uses an add-in digital signal processing board along with a consumer-class microphone and video camera and Microsoft NetMeeting and VDOPhone software. But for more flexibility, other dial-up systems add the capability of viewing the image on a TV screen, saving the session to a VCR, and providing other advanced features.
Dial-up videoconferencing systems have significant limitations, Intelect's Miracle says. Standard phone lines are limited to 33.6Kbps; ISDN, the phone line of choice for many videoconferencing systems, is 128Kbps; and uncompressed NTSC (National TV Standards Committee) signals require 81Kbps.
As a result, vendors must compress images or use a different format; JCI, for example, uses the Common Intermediate Format (CIF) that needs just 22Kbps uncompressed, but it delivers a significantly lower quality of image.
The key difference between high and low quality in videoconferencing is the degree of integration. Telecommuter-oriented products tend to have more software components, whereas LAN offerings and systems that produce high-quality images generally have greater amounts of hardware integration.
A range of options is out there, but choosing the right system requires knowing your expectations as well as your budget.
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