Virtual Conferencing Glossary

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Caller ID - An identification (number, name) of the party being called. This identification is of interest when you transfer or forward a call. For example, when an unanswered call is forwarded to a voice messaging system, the called-ID of the original call is used to locate the mailbox of the called party.

Camera presets - Allows pre-defined camera angles to be programmed into a videoconferencing system.

CAP set - Data passed between an MCS and a conferencing system that identifies the capabilities of the equipment, such as audio coding and transfer rate capabilities.

Carriage - Otherwise known as network protocol, carriage refers to the way in which videoconferencing signals are carried between endpoints. There are two main types of network protocols available. ISDN (integrated Services Digital Network), which takes the form of a dedicated digital phone line, or IP (Internet Protocol), which makes use of the Internet. The use of IP networks is growing momentum in the market place due to its high transmission capacity.

Cascading - Cascading as it relates to video conferencing is a process by which two or more bridges are connected to-gether to increase the number of ports available for a specific video conference. One of the primary benefits of cascading is that it is cost effective for geographically disparate video conferencing users. For instance, a corporation with 10 sites in Asia and another group of 10 sites in California could save money by cascading two bridges; one in Asia and one in California. This would allow multiple sites, in Cali-fornia or Asia, to connect utilizing only one link across the Pacific Ocean.

Chair-control video switching - A video-switching method using the ITU-T Recommendation H.243 standard in which a participant at a con-ference site selects the current broadcaster from the controls provided by the conferencing system. The con-ference must be using voice-activated video switching, and the H.243 Chair Control option must be installed at the site. Contrast with user-selected video switching. See also director-selected video switching; voice-activated video switching.

Channel negotiation - In the ISDN Q.931 protocol, the process by which a stored-program control system enables the equipment at the customer premises to request a channel that is different from the one indicated in the setup message.

CIF - Common Intermediate Format, an optional part of the ITU-T's H.261 and H.263 standards. CIF specifies 288 non-interlaced luminance lines, that contain 352 pixels. CIF is to be sent at frame rates of 7.5, 10, 15, or 30 per second. When operating with CIF, the number of bits that result can not exceed 256 K bits (where K equals 1024)

Circuit switched - An ISDN bearer service that provides a 64 kbps (sometimes 56 kbps) path between two users for the dura-tion of the call.

CODEC - A sophisticated digital signal-processing unit that takes an analogue input and converts it to digital on the sending end. At the receiving end, another codec reverses this by reconverting the digital signal back to ana-logue. Codec is a contraction of code/decode (some experts in the video industry assert it also stands for compress/decompress). A codec takes the form of a set of hardware or software components, or a combina-tion of both.

Collaboration - Collaboration allows for real-time viewing and/or modification of shared documents and files through the Internet. No special software is required for any number of users to view a shared document. Collaboration answers the need for teams in disparate locations to be able to work together simultaneously on a shared document.

Compressed video - By compressing normal TV transmission into a fraction of its former bandwidth by a codec, the resulting compressed video can be transmitted more economically over a smaller carrier. Some information is sacri-ficed in the process, which may result in diminished picture and sound quality. Squeezing the video informa-tion can be accomplished by reducing the quality (sending fewer frames in a second or displaying the infor-mation in a smaller window) or by eliminating redundancy.

Compression - Reducing the representation of the information , but not the information itself. Reducing the bandwidth or number of bits needed to encode information or encode a signal , typically by eliminating long strings of iden-tical bits or bits that do not change in successive sampling intervals (e.g., video frames). Compression saves transmission time or capacity. It also saves storage space on storage devices such as hard disks , tape drives , and floppy disks.

Computer mediated communication - Computer mediated communication (CMC) refers to communication conducted via online tools such as email, web pages, online interaction or conferencing.

Continuous presence - Continuous Presence (CP) is used if you want to see each site at the same time in a split screen mode (4 quadrants).

CPE - Customer Provided Equipment - Equipment not part of the public (ISDN) network, located and owned by the end user. This includes tele-phones, computers, terminals etc.