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Terminology


Algorithm
A step-by-step problem-solving procedure. Transmission of compressed video over a communications network requires sophisticated compression algorithms. Some videoconferencing systems offer both proprietary and standard compression algorithms.

Analog signals
Audio/video signals currently used in broadcasting where the signal is represented by variable measurable physical quantities (such as voltage). Current TV and radio signals are analog, as are many telephone lines. (Contrast with digital.)

Audio conferencing
Communication between three or more sites that are linked by a voice only telecommunications medium.

Bandwidth
In casual use, the amount of information that can be transmitted in an information channel. High bandwidth Internet access means those web graphics load quickly on Netscape. High bandwidth videoconferencing means that the picture and sound will be clear.

Bridge or multipoint control unit (MCU)
The piece of equipment that facilitates the communication of three or more sites in a videoconference.

BRI — Basic Rate Interface (ISDN)
Three digital signals over a single pair of copper wires: two voice (B) channels and one signal (D) channel. (e.g., voice and fax on a single pair of wires)

Codec (Coder-Decoder)
Videoconferencing hardware that codes the outgoing video and audio signals and decodes the incoming signals. Prior to transmission, the codec converts analog signals to digital signals and compresses the digital signals. Incoming audio and video must be decompressed and converted from digital back to analog.

Compressed video
When the vast amount of information in a normal television transmission is squeezed 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 sacrificed in the process, which may result in diminished picture and sound quality.

Continuous presence
Conference allowing each site to view other sites on a screen. Sites can be viewed in multiple configurations of a split screen.

Desktop videoconferencing
Videoconferencing on a personal computer. Most appropriate for small groups or individuals (compare with room-based videoconferencing). Many desktop videoconferencing systems support document sharing.

Dialing in
Each site initiates the video call by dialing into the bridge.

Document camera
A specialized camera used for taking pictures of still images (pictures, graphics, text pages) to be sent as part of a videoconference.

Document sharing
A feature supported by many desktop videoconferencing systems that allows participants at both ends of a videoconference to view and edit the same computer document.

Frame rate
Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps). Higher frame rates improve the appearance of video motion. Broadcast TV (full motion video) is 30 frames-per-second.

H.320 standard
A widely-used video compression standard that allows a wide variety of videoconferencing systems to communicate.

H.323 standard
A new standard providing a foundation for audio, video, and data communications across IP-based networks, including the internet. By complying to H.323, multimedia products and applications from various vendors can interoperate, allowing users to communicate without concern for compatability.

Multipoint videoconference
Videoconference with more than two sites. The sites must connect via a video bridge or multipoint control unit (MCU). (Compare with point-to-point videoconference.)

Point-to-point videoconferencing
Videoconference between two sites. (Compare with multipoint videoconference.)

Video bridge
Computerized switching system that allows multipoint videoconferencing.

Videoconferencing
Communication across long distances with video and audio contact that may also include graphics and data exchange.

Videostreaming
Streaming is a server/client technology that allows live or pre-recorded data to be broadcast in "real time," opening up the network for traditional multimedia applications such as news, training, entertainment, advertising, and a host of other uses. Streaming enables the internet or company intranet to act as a broadcast medium for audio and video.

Voice-activated videoconference
Refers to a type of videoconference in which the cameras are (1) activated by sound, (2) switch to the site where the sound is originating, (3) display that site on participant monitors.

Gatekeepers
Network management tools that control who gets access to which services and when. Gatekeepers also monitor service usage, network bandwidth and other network administration tasks. They perform the critical control, administration and management functions needed to maintain the integrity of enterprise local and wide area networks.

Multipoint Control Units (MCUs)
A multipoint control unit is designed to support simultaneous conferences between three or more locations. In H.323, the multipoint-session dynamics are very flexible. The standard allows for a variety of ad hoc conferencing scenarios, in addition to the traditional method of scheduled resource usage.

Gateways
Connect IP and circuit-switched networks; voice-only and/or multimedia. Gateways are essential network components for routing voice/video/data between H.323 based conferencing systems on IP networks and H.320-compliant systems over ISDN networks.

Terminals
End user devices that provide real-time, two-way communication; voice-only and/or multimedia


Last Updated: 07-21-2011

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