Frequently Asked Questions about videoconferences (FAQ)

Workgroup videoconference Russian version

What is videoconference?

- Videoconference is not only videophone on personal computer. Videoconference is the computer technology, which gives persons the opportunity to hear and to see each other, to exchange data, sharing data and collaboration using usual PC. To take part in videoconference your computer must have videoconferencing board and software. Additionally, you must have IP or ISDN connection with your college.

Why videoconferencing?

- To see your partner once is better then only to hear him 100 times. Most people prefer to watch news by TV, than to hear it by radio. Using videoconferences in management, business, telemedicine, security systems and many other areas is very useful.
Of course, videoconferencing cannot replace personal contacts. But it provides new level of people communication through thousands of kilometers. Special researches show that only 10% of information, translated by phone is accepting. If participant can see gesticulation and mimicry of other party, the percentage becomes 60%. Managers, who is already using videoconferences, believe that videoconferencing systems saves time and money for business trips and makes meetings more productive.

What are the main problems in videoconferencing?

- There are two. The first is that communication channel for transferring audio and video information shoud be wide enough. Usual telephone lines are good for audio but cannon provide quality video. But LAN is very good network for videoconference.
The second problem is processing of video and audio stream: coding and decoding of transferred data. The reason is that videoconferencing includes very high compression ratio algorithms especially for videostreams. If computer power is not sufficient for this algorithms, dropping of videoframes, jamming of audio can arise and so on.

What is necessary for videoconference?

Any videoconferencing terminal must have a few basic components to "get the job done": a camera (to capture local video), a video display (to display remote video), a microphone (to capture local audio), and speakers (to play remote audio). In addition to these more obvious components, a videoconferencing terminal also includes a codec ("COmpressor/DECompressor"), a user interface, a computer system to run on, and a network connection.

Which connections can be used for videoconference?

Videoconferencing is not currently a "plug-and-play" technology. Videoconferencing actually began over a decade ago with the introduction of expensive group conferencing systems designed to send and receive compressed audio and video over network connections that could guarantee a dedicated rate of transmission and predictable service (i.e., point-to-point T1 or fractional T1 communication links, switched connections using ISDN, or ATM). Standards surrounding how the audio and video would be compressed, how the endpoints would communicate with each other (i.e., initiating/terminating calls, negotiating audio/video compatibility, indicating error conditions during a call), and how the video streams would travel over the network eventually evolved but systems were not fully interoperable at the start. Still, evolution persisted and useful videoconferencing did finally emerge. Arguably the most popular and extensible early compressed videoconferencing was enabled via the ITU (International Telecommunications Union) standard called H.320. However, even with H.320, videoconferencing remained largely restricted to a) those who could afford the technology and network connections to establish meeting rooms, and b) those who were able to travel to a videoconference enabled meeting location.
As time has gone on, the above restrictions have lessened. The technology itself for conducting videoconferencing has become less expensive, more flexible, and now includes options for desktop videoconferencing as well as group videoconferencing. More ubiquitous network types, particularly TCP/IP as used on the Internet, are commonly used to provide less expensive and more flexible connections. In conjunction with this, a new ITU standard has emerged for supporting audio/videoconferencing over IP. This new standard, H.323, was first approved by the ITU in 1996 And has evolved through several additional versions since then and been implemented in a wide variety of commercially available products.

What bandwidth is sufficient for videoconference?

The picture quality depends on bandwidth. For CIF image size:
128 Kbit/s: 15 frames per second (standard quality)
256 Kbit/s: 20 frames per second (intermediate quality)
384 Kbit/s: 25 frames per second (high quality).

What to choose: hardware or software solution?

Hardware codecs are generally faster in completing their compression/decompression task, making near real-time communication more likely. Hardware codecs also often carry their own processing power "on-board" such that they do not rely on the resources of the underlying system. For instance, in the case of a desktop system, using a hardware codec may mean that you don't need a "souped-up" PC, or that you will be able to run other applications on your PC while simultaneously participating in a videoconference. On the other hand, software codecs are generally less expensive and easier to install (no special hardware required), but they tend to produce lower quality ("casual") conferencing with very low frame rates. In H.323 desktop videoconferencing systems, the codec typically resides on an interface board or in a software application. In H.323 group conferencing systems, the codec is most likely an interface board itself (you buy the PC) or is part of a turn-key system that is possibly proprietary but most likely PC- based.