Basic video conferencing involves capturing audio and video information and transmitting the captured signals to one or more of other users in the conference. A typical video conferencing installation includes apparatus for the capture and playback of audio and video information, apparatus for the electronic exchange of this information among at least two physically distinct and remote locations, and apparatus for managing the exchange of this information in an orderly manner among the distinct locations. Video conferencing system generally includes a local station and a remote station, commonly referred to as endpoints. Each video conferencing location includes a video conference processor, a video camera, a display, a microphone, and a speaker. Some of these elements may be combined within a single unit. For example, the housing for monitor may also include the video conference processor as well as the microphone and speaker. Each video conferencing location may also be equipped for data collaboration such as file sharing, a collaborative white board. In practice, an audio microphone and speaker with their associated electronic circuitry will serve as the apparatus for the capture and playback, respectively, of the audio information; a video camera and display with their associated electronic circuitry serve as the apparatus for the capture and playback, respectively, of the video information. Some video conferencing systems display a single image of a single participant to the other participants. Other video conferencing systems provide a split screen presentation with multiple display windows on a single screen, where each display window displays an image of a different participant (from different locations). Still other video conferencing systems allow multiple images to be presented on multiple screens, which may require specialized video display equipment. In video conferencing systems, video camera may be a separate, stand-alone device or may also be incorporated within the housing of monitor. The exchange of the audio and video information among the remote locations is typically carried across an electronic communications network which may be either analog or digital in nature, and the exchange of this information is typically managed by computerized equipment which has been programmed to assemble the various information into a virtual electronic meeting place.

Multipoint video conferencing is a service that permits to connection of three or more conference rooms, allowing a video, voice and data connection between all those participating in the session present in the rooms. A multipoint video conferencing system generally includes a multipoint control unit (MCU) which receives video signals from several different users and provides a single output video signal which can be simultaneously displayed to all users. The multipoint control unit is a conference bridge that connects the various end points of a single video conference session together when more than two end point devices are to be involved in the video conference. The multipoint control unit typically consists of a multipoint controller and one or more multipoint processors, which may be located on different network devices. The multipoint controller handles the call connection process in order to connect streams from endpoints to the multipoint processors. The multipoint processors perform the actual audio and video mixing. Each multipoint processor typically includes an audio mixer and a video mixer. One multi-point control unit can be used for a number of video conference sessions, where each session has two or more participants. The MCU links the sites together by receiving frames of conference signals from the sites, processing the received signals, and retransmitting the processed signals to appropriate sites. The conference signals include audio, video, data and control information. The audio, video and data signals associated with each participant are typically compressed by a user audio-video terminal (AVT) and sent to a multipoint control unit for further processing. The multipoint control unit performs switching functions to allow all of the three or more audio-video participants to communicate in a video conference. The MCU links multiple video conferencing sites together by receiving data units of digital signals from the audio-video terminals, processes the received data units and retransmits the processed data units to appropriate audio-video terminals as data units or frames of digital signals. A multipoint control unit typically has a plurality of connection ports, typically four, eight, twelve, or sixteen, and also includes the same number of line control units, which allows connection to the video conference equipments of the number of the ports as the upper limit.

A video conference typically includes full motion video presentations that are conducted across any number of communications networks and displayed on video conferencing systems located at the remote locations. Video images captured by camera at local station or endpoint are filtered and encoded by video conference processor prior to transmission to remote station or endpoint. Similarly, audio signals captured by microphone are filtered and encoded by video conference processor prior to transmission. The audio signals from two or more audio-video terminals are mixed to form a composite audio signal. The audio processing typically is relatively straightforward. The audio signals are decoded and summed to provide a composite signal. The composite signal is re-encoded as one audio signal and is transmitted to those terminals whose audio is not contained in the summed signal. At remote station, video and audio data received from local station are expanded and processed prior to display on monitor and speaker. Each endpoint will typically send both its audio stream and its video stream to the same multipoint processor. The multipoint processor will typically send one audio stream and one video stream back to each endpoint. The audio mixer and the video mixer use the same time base when generating timestamps for the mixed audio and mixed video streams so that each endpoint can achieve lip synchronization between the mixed audio and video streams. Videoconferencing technology has evolved over the years to the extent that it can compress the video and audio signals to a level that can be transmitted over relatively narrow bandwidths. Data compression allows an image or video segment to be transferred and stored in substantially fewer bytes of data than required for uncompressed frames.

Video conferencing systems are available in a wide range of systems with a corresponding variety of features and capabilities. Video conferencing systems have come into widespread use in the past several years, particularly with the merging of computers and telecommunications. Recently, the conferencing technology is becoming focused on digital techniques. With the availability of Internet access becoming less expensive and more widespread, it has become possible to implement the video conferences over the Internet or other similar data networks. As advances in microprocessor and other related technologies continue to improve the price/performance of various electronic components, video conferencing, including video conferencing conducted using personal computers, has become increasingly popular in recent years. Desktop video teleconferencing systems have recently been developed to take advantage of the relatively low-cost processing capability of today's personal computer systems as well as the increased processing power of personal computers. A video teleconferencing card set adapted for use in a host computer system typically comprises three individual computer cards, each of which must be installed into a corresponding card slot within the computer system chassis. Personal computer (PC) video conferencing systems offer a flexible video conferencing solution to the masses. With the addition of a video/sound board and a PC video camera, a standard home/business computer system may be transformed into a video conferencing system, while retaining all of the standard computing capability inherent in the computer system.