A real-time video session between two or more users that reside in two or more locations. While videoconferencing supports several end points communicating, the terms "video call" and "video chat" generally mean one-to-one. See video calling.
Although AT&T unveiled its expensive Picturephone at the New York World's Fair in 1964, there were few takers. Today, due to high-speed cable and DSL service, video calling has become commonplace for the consumer in the form of Apple's FaceTime and Microsoft's Skype. See FaceTime and Skype.
In the 1970s, business videoconferencing was established between branch offices, and by the early 1980s, more inhouse systems became popular after Compression Labs pioneered highly compressed digitized video. Digital video is delivered in various resolutions and frame rates starting at 128 Kbps up to multi-megabits per second.
Room Systems - The Beginning
In the early 1980s, videoconferencing emerged with room systems like this unit from Tandberg (the company was acquired by Cisco in 2010). (Image courtesy of Tandberg, www.cisco.com)
On the Desktop
Desktop videoconferencing became more widely used after the universal adoption of IP protocols in the late 1990s. Polycom's PVX software turns a Windows PC into a videoconferencing system. (Image courtesy of Polycom, Inc., www.polycom.com)
ISDN and IP
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 make the video of the dominant speaker the larger window on screen (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. Another option is to place the video system in the demilitarized zone (between the private network and the Internet). See DMZ
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