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Glossary
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Glossary
CIF
An abbreviation for Common Intermediate Format. This
format allows communication between different color
systems (NTSC and PAL).
352 pixels × 288 lines
Codec
An abbreviation for Coder-Decoder. An integrated device
of a coder that converts an analog audio/video signal to a
digital data stream and compresses it, and a decoder for
expanding to restore the original analog signal.
DHCP
An abbreviation for Dynamic Host Configuration
Protocol. Manages IP addresses in the network.
DNS
An abbreviation for Domain Name System. Defines the
domain name system server.
Echo Canceller
Device to eliminate echo that occurs when transmitting
audio.
Frame rate
The number of frames which can be encoded/decoded in
one second.
G.711
Audio encoding/decoding format recommended by the
ITU-T. A phone bandwidth audio signal is converted to a
digital signal with a data rate of 64 kbps. It can be
transmitted with a data rate of 56 kbps.
G.722
Audio encoding/decoding format recommended by the
ITU-T. A 7-kHz bandwidth audio signal is converted to a
digital signal with a data rate of 48 kbps, 56 kbps or 64
kbps.
G.728
Audio encoding/decoding format recommended by the
ITU-T. A phone bandwidth audio signal is converted to a
digital signal with a data rate of 16 kbps.
G.729
Audio encoding/decoding format recommended by the
ITU-T. A phone bandwidth audio signal is converted to a
digital signal with the data rate of 8 kbps.
Gatekeeper
Controls the access of H.323 videoconference devices on
a network. Administers the zone, access limitation, audio/
video bandwidth, and alias etc.
H.225.0
Frame structure for a 64 to 1920 kbps channel in
audiovisual teleservices.
H.239
ITU-T standard for sharing data and presentations with
video. This supports dual streaming, enabling endpoints to
receive and transmit video and presentation data
simultaneously.
H.261
Video codec for audio/visual services as p × 64 kbps.
Videoconferencing standard that defines a video coding
algorithm, picture format and error correcting technology
for communication between different manufacturers’
video codecs.
H.263
A video coding algorithm based on the H.261 standard.
This format enables communication via a lower bit rate.
H.263+
Video encoding/decoding format based on the H.263
standard, added by the Annex I to T (I, J, K …… T), that
allows enhanced picture quality and error resistance.
Normally, this format is a profile used with a combination
of some of the Annex for H.263/H.263+.
H.264
A video coding algorithm standardized by the ITU-T in
May 2003. This format realizes high-quality picture via a
lower bit rate. It provides an equal picture quality via half
as low bit rate as the H.263 format. The H.264 format is
also called as MPEG4 Advanced Video Coding (AVC).
H.323
This enables communications on the non-QOS (Quality of
Service) LAN.
HMLP
See “MLP”.
Lip synchronization
A function that synchronizes sound with motion. Sound
processing is much faster than motion processing, thus
sound and motion sometimes get out of step with each
other.
MCU
An abbreviation for Multipoint Control Unit. When
connecting a MCU, a multipoint videoconference can be
held.
