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Glossary
VTX Video Teleconferencing System - Preliminary
Codec
Coder-decoder. An electronic device that converts analog signals, such as
video and voice signals, into digital form and compresses them to conserve
bandwidth on a transmission path.
Compression
To compress video pixel-related data into compact mathematical
descriptions.
D Channel
Data channel The D channel is usually used for out-of-band signaling.
The two 64-kb/s clear channels are used for subscriber voice and data services. The
D-channel specifications are addressed in the CCITT Recommendation for the
Integrated Services Digital Network (ISDN). The D channel may be 64 kb/s for the
primary rate ISDN service.
Decompression
To decompress the compressed mathematical descriptions back
into pixels for display.
Desktop video teleconferencing
Video teleconferencing on a personal
computer. Most appropriate for small groups or individuals. (Compare with Room-
based video teleconferencing.)
Frame Rate
A measure of video speed, usually defined in number of frames per
second (FPS).
G.711
Standard for audio compression. Utilizes a large amount of bandwidth. Sound
coding protocol. 3.4 kHz (56/64 Kbit/s). Echo cancellation 200 ms.
G.722
Standard for audio compression. Utilizes the medium amount of bandwidth.
Sound coding protocol. 7 kHz (48 or 56 Kbit/s). Echo cancellation 128 ms.
G.728
Standard for audio compression. Utilizes the minimum amount of
bandwidth. Sound coding protocol. 3.4 kHz (16 Kbit/s). Echo cancellation 200 ms
Hardware Codecs
Video codecs that typically require hardware during
decompression.
H.221
H.221 is the frame structure for a 64 to 1920 kb/sec channel in audiovisual
teleservices. It is the protocol definition for carrying the family of protocols under
H.320, across the network. H.221 works without bit-stuffing, other HDLC-type
features, or start and stop bits usually used for framing on a WAN link, but rather
with a framing protocol. H.221 sends fixed sized frames of 80 bytes across the
network
Summary of Contents for VTX
Page 1: ...t a k e c o n t r o l VTX Video Teleconferencing System Instruction Manual PRELIMINARY ...
Page 10: ...6 Introduction VTX Video Teleconferencing System Preliminary ...
Page 14: ...10 Pre Installation VTX Video Teleconferencing System Preliminary ...
Page 54: ...50 Technical Support VTX Video Teleconferencing System Preliminary ...