InformationWeek SMB TechEncyclopedia

A real-time video session between two or more users that reside in two or more locations. While videoconferencing supports several end points communicating, the terms "video chat" and "videophone" typically mean one-on-one.

     The very first videoconferencing was done with traditional analog TV and satellites. In the early 1980s, inhouse room systems became popular after Compression Labs pioneered digitized video systems that were highly compressed. Video is delivered in various resolutions and frame rates over digital lines starting at 128 Kbps and going to multi-megabits per second. Major vendors in the field are Polycom (www.polycom.com), TANDBERG (www.tandbergusa.com), RADVISION (www.radvision.com) and VTEL (www.vtel.com).




Room Systems - The Beginning
In the early 1980s, videoconferencing emerged with room systems like this earlier unit from TANDBERG. Today, using flat panels instead of CRTs, similar systems are commonly used for small and large business groups. (Image courtesy of TANDBERG, www.tandbergusa.com)





On the Desktop
Desktop videoconferencing has become more widely used since the universal adoption of IP protocols in the late 1990s. Polycom's PVX software turns a regular PC into a videoconferencing system. (Image courtesy of Polycom, Inc., www.polycom.com)



ISDN and IP
ISDN was the traditional transport for digital videoconferencing because it provided dedicated channels end to end and allowed bandwidth to be dynamically allocated in multiples of 64 Kbps. Although still used, ISDN usage has mostly given way to networks that use the Internet protocol (IP).

     In a private IP network, either deployed by the enterprise itself or by using carriers, the quality can be controlled. Carriers such as International Video Conferencing (www.ivci.com) and Glowpoint, Inc. (www.glowpoint.com) specialize in high-quality backbones for high-speed conferencing traffic.

     Using the Internet as the transport provides reasonable quality without additional cost to users. Although periods of congestion are inevitable on a public network, systems can throttle down to lower frame rates to eliminate jerkiness, and users are willing to accept occasional blips. Using forward error correction, a videoconferencing system may be able to compensate for lost packets, but generally requires the same brand of equipment at both ends.

Multipoint Conferences and Telepresence
A point-to-point conference between two people is straightforward, but a conference with several people requires some moderating. A multipoint control unit (MCU) is used to mix the audio and make the video of the dominant speaker the larger window on screen (see MCU). Multipoint conferences are also achieved by connecting to a carrier's conferencing network service. A more immersive environment for group meetings is achieved with multiple monitors and loudspeakers (see telepresence).

Firewalls
Firewalls often present a problem for videoconferencing over the Internet because they are designed to block packets that have not been requested and thus stop a video caller. There are numerous ways of configuring routers and firewalls to accept videoconferencing data. Another option is to place the video system in the demilitarized zone (DMZ), which sits between the company's private network and the Internet (see DMZ).

Video PBXs
Like a telephony PBX, a video PBX is used to switch calls and provide call forwarding and call transfer, features that are becoming more important as videoconferencing becomes mainstream. Video network management is also required to adjust bandwidth, provide quality of service and log calls for accounting and billing purposes.

Summary
For years, the explosion of videoconferencing has been forecast to be right around the corner, but that corner has been farther down the road than expected. However, it is gaining significant ground within the enterprise, especially due to higher travel costs and the "green" movement. However, once videoconferencing has been established in a company, it has brought about a major benefit: it encourages more collaboration between workers.

     Due to cable and DSL service becoming ubiquitous, one-on-one videoconferencing ("videophoning") has accelerated for the consumer as well (see Metcalfe's Law). See videoconferencing standards and telepresence.