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A videoconference or video conference (also known as a video-teleconference) is a set of interactive telecommunication technologies which allow two or more locations to interrelate by two-way video and audio transmissions concurrently. It has also been called 'visual collaboration' and is a type of groupware.

Videoconferencing differs from a videophone calls in that it’s designed to provide a conference rather than individuals. It is an intermediate form of video telephony, first deployed commercially by AT&T during the early 1970s using their Picture phone technology.

                                                                      Tandberg T3 high resolution

                                                                A Tandberg T3 high resolution telepresence room in use

The core technology used in a video-teleconference (VTC) system is digital compression of audio and video streams in real time. The hardware or software that performs compression is called a codec (coder/decoder). Compression rates of up to 1:500 can be achieved. The resulting digital stream of 1s and 0s is subdivided into labeled packets, which are then transmitted through a digital network of some kind (usually ISDN or IP). The use of audio modems in the transmission line allow for the use of POTS, or the Plain Old Telephone System, in some low-speed applications, such as video-telephony, because they alter the digital pulses to/from analog waves in the audio spectrum range.

The other components required for a VTC system include:

  • Video input : video camera or webcam
  • Video output: computer monitor , television or projector
  • Audio input: micro-phones, DVD player, cassette player, or any other source of PreAmp audio outlet.
  • Audio output: usually loudspeakers associated with the display device or telephone
  • Data transfer: analog or digital telephone network, LAN or Internet
                                                                      Polycom VSX 7000 camera

                                 Dual display Polycom VSX 7000 camera used for videoconferencing with two displays
                                                                        for simultaneous broadcast from separate locations

There are basically two kinds of VTC systems:

  1. Dedicated systems have all required components packaged into a single piece of equipment, usually a console with a high quality remote controlled video camera. These cameras can be controlled at a distance to pan left and right, tilt up and down, and zoom. They became known as PTZ cameras. The console contains all electrical interfaces, the control computer, and the software or hardware-based codec. Omni-directional microphones are connected to the console, as well as a TV monitor with loudspeakers and/or a video projector. There are numerous types of dedicated VTC devices:
    1. Large group VTC are non-portable, large, more expensive devices used for large rooms and auditoriums.
    2. Small group VTC are non-portable or portable, smaller, less expensive devices used for small meeting rooms.
    3. Individual VTC are usually portable devices, meant for single users, have fixed cameras, microphones and loudspeakers integrated into the console.
  2. Desktop systems are add-ons (hardware boards, usually) to normal PCs, transforming them into VTC devices. A range of different cameras and microphones can be used with the board, which contains the necessary codec and transmission interfaces. Most of the desktops systems work with the H.323 standard. Videoconferences carried out via dispersed PCs are also known as e-meetings

Connecting

The most significant distinction among videoconferencing systems is the method of transmission. Transmission is significant because two systems cannot connect if they are using different transmission methods. Videoconferences can be transmitted over two protocols, H.320 - ISDN (phone) or H.323 - IP (Internet) lines. In the past, most videoconferences used ISDN lines; however, many people are now using IP connections due to cost savings. In order to connect two units using different transmission methods, a bridge must be used that will hold these mixed protocols. In an ISDN call, bandwidth is dedicated to only one videoconference, while in an IP call; bandwidth may be used to transmit for multiple uses. However, ISDN calls can be extremely costly since you may be making the call over a distance, in which case, long distance phone line charges apply, and ISDN lines take up 6 phone lines. Connections around the world average 384 kbps.

Benefits

Educators and librarians from around the country report videoconferencing technology impacts student learning in a number of ways. Teaching professionals have observed that two-way videoconferences improve students' motivation, and improve communication and presentation skills. Additionally, a virtual field trip increases the intensity of learning and provides a forum for a greater connection with the outside world.

A videoconference can improve students' memory preservation by appealing to a range of different learning styles by including different media such as video and audio clips, graphics, animation, and computer applications. Videoconferencing connects previously contained institutions in a way not possible using e-mail, the telephone, or online chat systems. The visual connection and interaction among participants boost understanding and allow both the content providers and the students to feel connected to one another. That connection leaves a distinct impression on the students who have the opportunity to go on a virtual field trip.

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