An MCU enables multi-location video conferencing by providing a sort of “central processing center” for all of the locations through which all the information flows. The MCU receives all information from the various locations and then sends it out to each location. In some cases the MCU is located on a particular PC, and in other cases it is located on a remote server (the most common structure, particularly for more powerful MCU networks).

Audio is usually sent and received simultaneously in all locations with an MCU with no problem because of the relatively small bandwidth needed for transmittal. It is broadcast in what is called “full duplex” mode, meaning everyone can talk and hear at the same time with no cutting off when one person or another speaks.

Video transmission, however, can be broadcast in a number of ways with an MCU depending upon the quality of the software and the complexity of the system. Some common types of video transmission for video conferencing include:

• Continuous Presence video conferencing, which allows up to four conference sites to be seen simultaneously on split screens. This is usually used if you have a small group or individuals in separate locations and will primarily be seeing close-up shots.
• Universal Control video conferencing is controlled by the initiating conference site. The primary site determines who sees what at all other sites.
• Voice Activated video conferencing is by far the most common type used today. The image with these systems shifts to the site that is currently activating the microphone so that you can always see whoever is speaking. However, if there is a good deal of background noise participants should mute their microphones when they aren’t talking in order to avoid the image jumping about needlessly.

Overcoming the language barrier

Obviously, communicating through video conferencing can’t be achieved unless both ends of the conference are “speaking the same language.” That is, whatever is being transmitted electronically will need to be reassembled properly and heard and seen clearly at the other end. The Codec system (Coder-Decoder) is useless if both ends aren’t using the same virtual language to interpret the signals.

The International Telecommunications Union (ITU) developed a set of standards in 1996 dubbed H.323 to outline specific guidelines for Video Conferencing standards and protocols so that compliance and support across networks would be easier to achieve and maintain. Since then, many manufacturers and developers of video conferencing tools have adopted the H.323 guidelines as their own.

Web conferencing solutions such as Click to Meet, Lotus’s SameTime, and WebEx also offer corporate solutions that are based on Internet video conferencing. These systems have shared protocols that can be downloaded and used anywhere at any location for subscribers through the Internet. These are becoming more popular with companies who like the convenience and user-friendliness. They will no doubt become more and more refined over time, vying with and perhaps surpassing the H.323 standards.