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Appendix C: Glossary
Abbreviation/Term Explanation
Bandwidth
Defines the information-carrying capacity of a channel. In
analog systems, it is the difference between the highest
frequency that a channel can carry and the lowest, measured
in hertz. In digital systems, bandwidth is measured in bits per
second. The larger a connection's bandwidth, the more data
can be transmitted in a given amount of time, allowing for
greater video resolution and more sites in a conference.
Bps, Kbps
Bits and kilobits per second--a unit of bandwidth--that is the
amount of data that can flow during one second over a
communications line (using a transmission medium).
1Kbps=1000Bps
CIF, 4CIF, QCIF
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 176 pixels. CIF
can be sent at frame rates of 7.5, 10, 15, or 30 per second.
When operating with CIF, the amount of data to transmit
cannot exceed 256K bits. The CIF video format has the
capacity to transmit video images of 352x288 pixels at
36.45Mbps and 30 frames per second. A 4CIF format has
four times the capacity of CIF; QCIF has quarter the capacity
of CIF.
Codec
Coder-decoder. A device that converts voice and video into
digital code and vice versa. Refers to the endpoint video
camera and video board that are used for videoconferencing.
Conference
Connection between two or more endpoints exchanging
video and audio information. If only two endpoints are
involved, a conference is called point-to-point and no MCU is
required. If more than two endpoints are involved, it is called
a multipoint conference, and an MCU (Multipoint Control
Unit) is required as the management system.
DTMF
Dual Tone Multi-Frequency. A system of coded signals used
by touch-tone telephones in which a specific sound,
frequency, or tone is assigned to each key so that the signal
can be easily recognized by a computer. The codes enable
data input and control of voice-processing systems. DTMF
signals can pass through the entire connection to the
destination device and therefore are used for remote control
after the connection with the MCU is established.