How is it done? Video conferencing used to be something of a black art. Today, easy-to-use and manage technology means that users need know little about how the equipment actually works. What's important is what it can do, not how it does it

Telecom Asia, Dec, 2002

VC systems have evolved into four main types due to the different `types' of conference users actually want to engage in--each is appropriate in different circumstances, or for different types of organization or VC application.

Appliance-like Group Systems

These were introduced in the late 1990s and greatly improved usability over "legacy systems" which usually required a technician to manage the call. Based on the principle of a home appliance, which is designed for a dedicated purpose and is very easy to use, these systems liberated and empowered the user of video conferencing. They are designed to sit on top of a standard TV monitor and run over ISDN or IP networks.

The camera and processing technology are in one `box' which can be remote-controlled through graphical, on-screen menu. Dialling calls, zooming in and out on both the near and far end, and troubleshooting are as simple as pushing a button. And there are additional connectivity options, such as the ability to add extra microphones, a second or third camera and extra TV monitors. There are also PC interfaces for data collaboration (see pages 4-5).

Multimedia Conferencing Systems

When sharing and working on documents is the highest priority for a business team, multimedia conferencing systems are the right choice. Characterized by PC-style interfaces, these systems enable users to easily incorporate collaboration tools into their VC sessions with point-and-click functionality. The systems integrate information from a laptop, a local network, the Web, and other devices like document cameras, projectors, and VCRs, into the videoconference. They allow users to see both the people and the information live at highest resolution all the time, regardless of where the data originates. They also can function as multimedia centres for local, in-room meetings, not involving remote participants (i.e., not a video conference).

Installed Room Systems

Sometimes the room where the video conferencing is to take place, or the application itself, requires that a system be custom designed into the facilities. These are known as installed systems, or custom systems. Executive boardrooms and classrooms are classic examples where such systems may be preferred. The "codec" for the system is separate from the camera and microphones so that it can be built into the cabinets of the room, and cameras and microphones can be placed strategically around the room for maximum impact.

Personal or Desktop Systems

Video conferencing at the desktop has also reached a critical juncture of acceptance. Previously desktop conferencing was available in two extremes:

* Users could mount a small `webcam' on a PC and run a software program, but they suffered poor sound and bad visuals as their applications struggled with a lack of processing power.

* Users could crack open their PCs to install video cards for a fully-integrated system. These offered better quality but were cost-prohibitive for mass deployment throughout an organisation.

Today, a third product category has been introduced which offers professional, conference-room quality video conferencing at the desktop at low cost and great ease-of-use.

Regardless of the structure of the equipment, elements for VC include:

* Cameras: A camera at each site captures the picture to be transferred to the other site(s). Today, cameras range from tiny, basic PC-mounted cameras to highly sophisticated cameras which can pan, tilt, zoom, and even track speakers' voices automatically to make the experience of being in a video conference as lifelike as possible. Cameras can either be built as an integrated part of a VC system or remain stand-alone for customized positioning.

* Screens: Some form of screen or monitor is needed from which participants view the video images of those at the `remote end'. These can be PCs, television sets, plasma screens or other dedicated video screens and projection units.

* VC Systems: The engine of a video conferencing system, or `endpoint', is a codec (COder/DECoder) which codes the analogue signal into a digital signal and then undertakes the all-important task of compressing the video and audio streams. Without digital compression techniques video conferencing would soak up unfeasible amounts of network bandwidth. As described above, codecs can be either the set-top boxes integrated with a camera, or separate rack-mountable boxes which can be hidden away in an A/V cabinet and the camera(s) strategically placed for custom-room fittings.

In addition, to enhance the capabilities of a conference, other components may be required:

* Gateways: are designed to `bridge' different video conferencing systems' coding standards, enabling conferencing to be conducted between different video conferencing types and networks.

* Multipoint control units--MCUs

When more than two sites are involved in a conference, an MCU is required and conference management becomes critical. Some video conferencing systems have built-in MCUs which allow users to dial up to four parties into a call at the click of a button, and now some systems allow you to buy optional internal MCUs that connect up to 12 sites! However, when multiple multi-party, complex videoconferences are the norm for an organisation, an external MCU is often recommended. Robust MCUs will allow numerous conferences, each made up of several sites, to take place at one time, and they will also serve as gateways to facilitate cross-network (e.g. IP to ISDN) conferences. They also carry out "transcoding" which allows sites with different frame rates, connection speeds, audio algorithms, resolutions, and network protocols to transparently connect with one another. In addition, MCUs orchestrate sessions by organising (and allowing users to dictate) the appropriate display for each participating site for maximum viewing effectiveness.