Video Conferencing Terms
- A set of specifications that define methods and procedures for transmitting
audio, video, and data.
- A means of connecting dissimilar codecs. Incoming digital signal from one type
of codec is decoded by a similar codec and converted to analog. The Analog
signal is then passed to the dissimilar codec, coded, and decoded at the far
end. Analog gateways achieved interoperability in a nonstandard environment, but
have the disadvantages of degrading video and audio quality and often reducing
An addendum to the H.320 videoconferencing protocol used for still image
transfer between dissimilar videoconferencing systems.
- Asynchronous Transfer Mode. An emerging networking method that can be used for
carrying voice, video and data simultaneously over low speed (T1 - 1.5 Mbps) or
very high speed (622 Mbps) networks.
- Amount of transmission capacity.
Interface (BRI) - An ISDN access or subscriber line, consisting of two 64Kbps B
("bearer") channels and one 16Kbps D channel used for both data and
- One-way video, usually from a single transmitting site to many receiving
sites. In some cases, the receiving sites can communicate to the transmitting
site on an audio-only basis.
- International Telephone and Telegraph Consultative Committee. Now known as ITU-T.
An international body that sets worldwide telecommunications standards, such as
the Px64 standard for videoconferencing.
- Used to divide a T1 access facility into 24 digital or analog circuits.
Unit (CSU) - A type of customer premise equipment that terminates a T1 access
facility to a channel bank, PBX or other equipment capable of supporting a T1
- Coder-Decoder: a device that encodes an incoming analog signal into a digital
signal for transmission to another codec. The digital signal is decoded into
analog format. In videoconferencing, codec typically code an decode video and
- Reduction of the amount of information to accommodate cost-effective digital
transmission to another codec. For example, sub-T1 video codecs compress analog
signals (roughly equivalent to 90,000 kilobits per second) to digital rates
varying from 56 to 1,544 kilobits per second.
Ratio - A
compression ratio, usually expressed as 5:1, refers to the size of the original
data versus the size after compression. If data has been reduced to one-fifth
the original size, the compression ratio is 5:1.
- A permanently assigned path connecting geographically dispersed sites on a
long distance network. Synonym: private line: leased line.
- Refers to the slight delay that sometimes occurs when transferring video, data
and audio signals.
- Digital Encryption Standard, an encryption method defined by the National
Bureau of Standards.
- Information contained in the form of 0s and 1s for transmission on digital
media, including fiber, microwave, and satellite. Digital information may
include video, audio, graphics, and data.
Unit (DSU) - A type of customer premises equipment that terminates a single DSO or
- Digital Signal level zero. One 56Kbps (or 64Kbps) line or circuit.
- Digital Signal level one. One 1.544Mbps digital signal comprised of 24 lines
or channels, each with 64 Kbps capacity (see T1).
- A means of supporting multiway conferencing using the signals in their digital
format without converting them to analog. Digital switches permit multiple users
with similar codecs to conference generally with voice-activated switching.
- Combination of two 56Kbps lines for a 112Kbps video transmission capacity.
Dual 56 typically allows direct dialing of a videoconference call.
- High speed 2.048Mbps digital line with 32 channels, each operating at 64 Kbps.
E1 is only available outside the U.S.A.
- Alteration of transmitting information to protect it from unauthorized
FCIF or (CIF)
- Full Common Intermediate Format. A video resolution of 352 pixels horizontally
and 288 pixels vertically. It is used primarily in higher bit rate (128Kbps and
higher) video conferencing.
- Memory which occupies little space and does not need continuous power to be
- Frame Relay Access Device: F.R.A.D. takes the information streams and
multiplexes them on public or private frame relay networks.
- A packet switched networking technology used for low speed (T1 - 1.5Mbps and
lower) WAN connections. Primarily used to connect a company's routers on their
- Frequency with which video frames appear on a monitor. Broadcast-quality video
generally consists of 30 frames per second. Full-motion videoconferencing
typically offers video in the range of 10 - 15 frames per second. At very low
bandwidths, such as 56 or 112 Kbps, the frame rate may be lower.
that allows local and remote conference participants to speak simultaneously
with out losing audio contact. Full-duplex audio may be provided in a
point-to-point or multipoint conference.
- In compressed video, picture quality that is generally acceptable to users
although not of broadcast quality. Typically full-motion compressed video
provides anywhere from 10 - 30 frames per second depending on the bandwidth
- Transmission of still images, usually from a video source, but in some cases
- 3KHz audio-coding at 64Kbps.
- 7KHz audio-coding at 64Kbps.
- 3KHz audio compression at 16Kbps (wideband audio).
Audio that permits only one site to speak at a time.
- The ITU-T standard relating to communications protocol for videoconferencing.
- The ITU-T standard that defines call control and indication.
- Multipoint for linking three or more H.320 codecs.
- Call set-up and disconnect of two point videoconferencing.
- Defines call control procedures between H.231 MCU and H.320 codecs.
- The ITU-T Px64 standard relating to the video compression algorithm.
-Umbrella standard for videoconferencing.
- Video over LAN/WAN.
- Video over POTS.
- Transmission taking place within allocated bandwidth. For example, a video
call with total of 384Kbps may allocate 64 Kbps for audio, leaving 320Kbps for
Presentation System - Presentations such as those created in Microsoft® PowerPoint®, can
be displayed and presented to the far site while simultaneously being presented
to remote users connected via the Internet/Intranet.
- Communication in which all participating sites have equal capability.
Interactive videoconferencing permits all sites to see and hear one another.
- Communication between dissimilar codecs. The ITU-T Px64 standard is designed
to permit interoperability.
Multiplexer (Imux) - A device that creates a single higher-speed transmission by combining
and synchronizing two or more channels.
(Integrated Services Digital Networks) - A switched network service providing end-to-end
digital connectivity for transmitting voice, data, and video simultaneously over
a single line verses multiple. Uses high-speed, out-of-band signaling. There are
two major forms of ISDN: BRI and PRI.
- International Telecommunications Union-Telephony Sector. Formerly known as
CCITT. An international body that sets worldwide telecommunications standards,
such as the Px64 standards for videoconferencing.
- Joint Pictures Experts Group. Still-frame graphics for multimedia.
- Measure of rate of digital transmission, often abbreviated Kbps.
- Local Exchange Carrier; provides local telecommunications service and access
to long distance networks.
- The communications lines between the long distance subscriber and the LEC
- A diagnostic test where a signal is transmitted over a communications link or
network and then returned to the sending device. Loopbacks are used to make sure
the video equipment is working properly and as a way to demonstrate
- A device that permits subdivision of a given bandwidth. For example, a T1
Multiplexer may divide a T1 line (1,544Kbps) into two capacities of 768Kbps
- Motion Pictures Experts Group: This is a standard for motion video.
- Communication between more than two sites. Multiway communication may occur
through a digital switch or through an analog gateway.
- Device which allows more than two sites to be connected in a videoconference.
Sometimes called a digital switch or video bridge.
- North American standard for analog video format. National Television Systems
Out of band
- Transmission taking place external to allocated bandwidth. A video call with
out-of-band audio requires a separate phone line for the audio.
- European standard for analog video format.
- Picture element; a measure of resolution for video format.
Interface (PRI) - An ISDN subscriber line consisting of 23 64Kbps B channels and one
64Kbps D channel used for signaling.
- Point-of-Presence. The location or office where a line from an Inter-Exchange
Carrier (IXC) connects to the local telephone company or directly to the user.
- Plain Old Telephone System. The analog phone system (including telephones,
modems, central offices switches, etc., currently in use around the world.
- The ITU-T's international video standard which provides a standard algorithm
for video compression and decompression. Formally known as H.261, it was adopted
in December 1990.
- Quarter Common Intermediate Format. A video resolution of ¼ the size of FCIF
- 176 pixels horizontally and 144 pixels vertically. It is used primarily ion
low bite rate (128Kbps and lower) videoconferencing.
- Regional Bell Operating Company; controls a grouping of local exchange
- A measure of sharpness or clarity on a monitor.
- Resource Reservation Protocol. An emerging data network standard protocol used
to reserve bandwidth within packet networks. It is primarily used in data
network routers to guarantee a fixed bandwidth through the router for a single
or group of users using real time data (like voice or video). All other traffic
not assigned to the reservation (such as e-mail or Web access) is delivered by
best effort by the router (as it is today).
- Connectivity from the codec permitting data inputs for transmission from .3 to
- Transmission interface between the codec and the transmission link that
typically connects to a t1 Multiplexer. A user RS-449 port may also be available
for data transfer.
- French standard for analog video format.
- Simple Network Management Protocol; the protocol governing network management
and monitoring of network devices and their functions. SNMP came out of the
- Uniform specifications to permit interoperability in videoconferencing.
- Transmission network at 56Kbps that allows dial-up videoconferencing. Because
picture quality at 56Kbps is often not acceptable, most dial-up
videoconferencing takes place on two 56Kbps lines, for a total of 112Kbps (see
- The international standard protocol used on the Internet and company data
networks. It provides worldwide connectivity and includes serves such as the
World Wide Web, e-mail, file transfer and remote terminal login.
Speed - Data
rate for videoconferencing, usually expressed in Kbps.
- Commonly used transmission line for videoconferencing, with a capacity of
- Multilayer protocols for graphics/data transmission.
- A 45Mbps leased line. Usually obtained from a local or long distance telephone
- Communication across long distances with video and audio contact.
Switching - In multiway videoconferencing, used so that all participating sites
automatically see the site which is currently speaking.
- camera automatically tracks the voice of the person speaking.
- Transmission interface between the codec and the transmission link that
permits Switched 56 connectivity.
- A computer that delivers (serves up) Web pages. Every Web server has an IP
address and possibly a domain name. For example, if you enter the URL http://www.sandybay.com/
in your browser, this sends a request to the server whose domain name is
sandybay.com. The server then fetches the page named and sends it to your
- A software application used to locate and display Web pages. Three of the most
popular browsers are Netscape Navigator, Microsoft Internet Explorer, and
Spyglass Mosaic. All of these are graphical browsers, which means that they can
display graphics as well as text. In addition, most modern browsers can present
multimedia information, including sound and video.