What is a Videoconference

A Videoconference is the transmission of audio and video between two or more parties. Whether we realize it or not we have all witnessed videoconference in action. On any night we turn on the TV to our favorite national news coverage. The news anchor talks to a reporter in the field, the anchor can see and hear the reporter and the reporter can see and here the anchor, fundamentally they are using a videoconference technology. This technology really became popular during the Iraq war. A reporter in Iraq would use videoconference technology to enable live updates during the evening news. Another great example of videoconference technology is the Star Trek view screen. We see the Captain of the enterprise conversing with other ships and other Captains using both video and audio. These are examples of a two-way videoconference; another common use of videoconferencing is a multi-site conference.

What is a Multi-site Videoconference?

A multi-site videoconference requires the use of a bridge. This 'bridge' allows three or more videoconference sites to be connected to one another. The participants can view the bridged videoconference in two ways:

• Voice Switched: When using voice switched technology the video being displayed to participants is that of the current user who is talking. When another user begins to talk (or takes the chair) the video signal being displayed on all the end users systems switches to that person.
• Continuous Presence: This is most often used by smaller bridged videoconferences, 3 to 4 sites. When this option is selected on the bridge the users see all the sites displayed at the same time on one screen in a split screen or picture-in- picture (PIP) configuration.

Why not just use a web cam and a video chat program?

Commonly used desktop videoconference applications that use web cams such as MSN and iChat use a slightly different technology than industry standard videoconference systems. These desktop programs use software that connects to a server run by the distributor of the software. They are intended for person-to-person conferences and rely on commercial Internet connections. As such they are subject to degradation of the Internet connections and lost video or audio signal. While these programs are great for talking to friends and family they do not compare in quality to high-end systems.

An industry standard videoconference system can connect in two ways:

• IP (internet protocol). This is what your home internet connection uses. and;
• ISDN. ISDN connections are dependant on the number if data phone lines conneted to your system the more phone lines the better your connection (often ranging from 2 lines of 64k to 8 lines of 64k).Many larger institutions are connected to research network such as CaNet4, which allows them to run videoconferences ranging from 768kbs to 4Mbs, compare this with desktop videoconference software, which can range from 100kbs to 300kbs.

What does this all mean?

The faster the connection between the videoconference sites the better the quality. Lets compare this to streaming video. A video you would commonly view on the web usually runs around 50kbs - 100kbs. Now a DVD that you play in your desktop machine at home runs between 4Mbs and 7Mbs. This means that a videoconference using a research Network and running at 4Mbs is DVD quality. This means a clear picture and perfect audio.