Appendix A - Glossary - Polycom RealPresence 800s Getting Started Manual

Glossary
This appendix lists the terms and abbreviations that are related to the RealPresence Collaboration Server
800s/Virtual Edition, and are commonly used in the Collaboration Server documentation.
Abbreviation/Term
AGC
Bandwidth
Bps, Kbps
Carrier
CIF, 4CIF, QCIF
Codec
Conference
CSU
DBA
Polycom®, Inc.
Explanation
Auto Gain Control. A mechanism that regulates noise and audio volume by keeping the
received signal of all participants balanced.
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. For more
information, see Line Rate.
Bits and kilobits per second; a unit of bandwidth, which is the amount of data that can flow
during one second over a communications line (using a transmission medium).
1 Kbps = 1000 Bps
A telephone or other company that provides telecommunication transmission services.
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 256 K bits (where K equals 1024).The CIF video format has
the capacity to transmit video images of 352x288 pixels at 36.45 Mbps and 30 frames per
second. A 4CIF format has four times the capacity of CIF; QCIF has quarter the capacity of
CIF.
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 video conferencing.
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. For more
information, see MCU.
Channel Service Unit. Customer-provided equipment that is used as an interface between
a communication network and the data terminal.
Dynamic Bandwidth Allocation. Used to allocate the bandwidth needed to transmit the
additional packets for LPR.
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