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Related to Videotelephony: Video phone


A real-time video session between two or more users who reside in different locations. While videoconferencing supports several end points, the terms "video call" and "video chat" generally mean one-to-one. However, all the terms are used synonymously. See video calling and computer audio.

In 1964, AT&T unveiled its Picturephone at the New York World's Fair, but it was very expensive and there were few takers. Today, due to high-speed Internet access, video meetings have become commonplace for everyone with services such as Skype, FaceTime, Google Meet and Zoom (see videoconferencing software).

It Used to Be Only for Companies
In the 1970s, business videoconferencing was established between branch offices. By the early 1980s, in-house systems became popular after Compression Labs pioneered highly compressed digital video to shorten the data being transmitted over much slower lines than we now have. Ever since, various resolutions and frame rates have been used with speeds from 128 Kbps to multi-megabits per second.

Room Systems - The Beginning
In the early 1980s, videoconferencing emerged with room systems like this unit from Tandberg, which Cisco acquired in 2010. (Image courtesy of Tandberg,

Early Internet Videoconferencing
Desktop videoconferencing became widely used after the universal adoption of Internet protocols in the late 1990s (see IP). This software from Polycom (now Poly) turned a Windows PC into a videoconferencing system. (Image courtesy of Poly,

ISDN was the traditional transport for private videoconferencing because it provided dedicated 64 Kbps channels that could be dynamically allocated. However, ISDN gave way to the Internet protocol (IP). In a private IP network deployed by either the enterprise or via carriers, the quality can be controlled.

Using the public Internet as transport provides reasonable quality without additional cost. Although congestion is inevitable, systems can throttle down to lower frame rates to eliminate most of the jerkiness.

Multipoint Conferences and Telepresence
A point-to-point conference between two people is straightforward, but a conference with several people requires moderating. A multipoint control unit (MCU) is used to mix the audio and highlight the frame of the dominant speaker or make it larger, which is necessary in large groups (see MCU). Multipoint conferences are also achieved by connecting to a carrier's conferencing network service. A more immersive environment for group meetings is achieved with multiple monitors and loudspeakers (see telepresence).

Firewalls often presented a problem for Internet videoconferencing because they are designed to block packets that were not previously requested. However, there are numerous ways of configuring routers and firewalls to accept videoconferencing data. A common method is to invite participants, who then click links to initiate a request. Another option is to place the video system in the demilitarized zone between the private network and the Internet (see DMZ).

Video PBXs
Like a telephony PBX, a video PBX is used to switch calls and provide call forwarding and call transfer. Video network management is also required to adjust bandwidth, provide quality of service (QoS) and to log calls for accounting purposes. See videoconferencing standards.
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A means of simultaneous, two-way communication comprising both audio and video elements. Participants in a video telephone call can both see and hear each other in real time. Videotelephony is a subset of teleconferencing, broadly defined as the various ways and means by which people communicate with one another over some distance. Initially conceived as an extension to the telephone, videotelephony is now possible using computers with network connections.

Small residential video telephones, computer-based desktop video telephones, and small videoconferencing setups have been introduced to fulfill diverse needs. One such commercially available residential videophone is about as big as a typical office desk telephone with a small flip-up screen that has an eyeball camera above it. Although it will work with several standards, this phone is primarily designed for use over Integrated Services Digital Network (ISDN) lines in which a residence gets three circuits; one circuit is used for control and the other two for voice and video. See Integrated services digital network (ISDN)

An example of a computer-based desktop videophone consists of a PCI (Peripheral Component Interconnect) video/audio CODEC board to add to a personal computer, a composite color camera, audio peripherals, and visual collaboration software.

Videotelephony software has been developed and made widely available that permits real-time collaboration and conferencing, including multipoint and point-to-point conferencing. Multipoint means, for example, that three people in three different locations could have a video telephone conference call in which each could see and hear the others. In addition to the basic audio and video capabilities, such software provides several other features such as a whiteboard, background file transfer, program sharing, and remote desktop sharing.

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Videotelephony is real time, two-way communication via the Internet using audio and video.
It is able to transmit images via live streaming to any phone capable of receiving videotelephony and can be used for sending e-mails and MMS messages.
For example, videotelephony has been reported as commercially unsuccessful (Noll, 1992), with Kraut and Fish (1997) concluding that this technology is more likely to find application in the home.
body governing international recommendations for videotelephony and multimedia communications across virtually all the networks likely to impact large and small corporations (as well as homes and home offices).
The Internet is a crude prototype of such a multipurpose single network, with mail, Web traffic, telephony, videotelephony, and Mbone narrowcast video conferences all coexisting on the same communications links.
With advances in digital-coding technologies, it will support high-fidelity audio and limited forms of videotelephony over telephone lines.
Ever since the launch of FaceTime, ( Apple 's proprietary videotelephony application only enabled one-on-one conversations.
Nokia's UltraSite is a multimedia-ready system supporting HSCSD, GPRS, EDGE and wideband CDMA, and it will enable a variety of new mobile multimedia applications, such as videotelephony, infotainment, mobile Internet and intranet access at home.
In videocommunications the distinction is generally made between videotelephony and videoconferencing.