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.

Gatekeeper

Controls the access of H.323 videoconference devices on a network. Administers the zone, access limitation, audio/video bandwidth, and alias etc.

H.221

Frame structure for a 64 to 1920 Kbps channel in audiovisual teleservices.

H.261

Video codec for audiovisual 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.320

A videoconferencing standard for communication between different videoconferencing system.

H.323

This enables communications on the non- QOS (Quality of Service) LAN.

HMLP

See “MLP”.

I-MUX

An abbreviation for Inverse Multiplexer. This protocol allows you to transmit the data at 384 Kbps via 6B-channel.

ISDN

An abbreviation for Integrated Services Digital Network. This is a communication protocol by CCITT on transmission of integrated voice, video, and data. Bandwidths include basic (64 Kbps) and primary rate (1.544 and 2.048 Mbps).

ITU-T

An abbreviation for International

Telecommunication Union,

Telecommunications.

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.

MLP

Data communication is also available during communication of video/audio signals between the videoconferencing systems. The MLP or HMLP is a protocol for data communication such as NetMeeting. Using the HMLP protocol allows faster data transmission.

PBX

An abbreviation for Private Branch exchange.

P in P

An abbreviation for “Picture in Picture.” This is a function which allows you to monitor your own party on a small window on your TV monitor.

QCIF

An abbreviation for Quater CIF. The number of pixels is a quarter than one of CIF format. 176 pixels × 144 lines

Appendix

Glossary 181