videoconferences' meaning????????

A videoconference (also known as a videoteleconference) is a set of interactive telecommunication technologies which allow two or more locations to interact via two-way video and audio transmissions simultaneously. It has also been called visual collaboration and is a type of groupware. It differs from videophone in that it is designed to serve a conference rather than individuals.

[edit] History
Video conferencing uses telecommunications of audio and video to bring people at different sites together for a meeting. This can be as simple as a conversation between two people in private offices (point-to-point) or involve several sites (multi-point) with more than one person in large rooms at different sites. Besides the audio and visual transmission of people, video conferencing can be used to share documents, computer-displayed information, and whiteboards.

[edit] Technology

A modern dual plasma video conferencing system. The Plasma on the left is primarily used to show people during the conference or the user interface when setting up the call. The plasma on the right is used to show data in this case but can be used for displaying a 2nd 'far site' in a multipoint call.The core technology used in a videoteleconference (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 1's and 0's is subdivided into labelled 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 videotelephony, because they convert 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: microphones
Audio output: usually loudspeakers associated with the display device or telephone
Data transfer: analog or digital telephone network, LAN or Internet
There are basically two kinds of VTC systems:

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. Omnidirectional microphones are connected to the console, as well as a TV monitor with loudspeakers and/or a video projector. There are several types of dedicated VTC devices:
Large group VTC are non-portable, large, more expensive devices used for large rooms and auditoriums.
Small group VTC are non-portable or portable, smaller, less expensive devices used for small meeting rooms.
Individual VTC are usually portable devices, meant for single users, have fixed cameras, microphones and loudspeakers integrated into the console.
Desktop systems are add-ons (hardware boards, usually) to normal PC's, 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. Video conferences carried out via dispersed PCs are also known as e-meetings.

視像會議

視像會議能作雙方或多方之視像溝通，並且傳送圖表和資料影像使溝通更為全面。

A videoconference (also known as a videoteleconference) is a set of interactive telecommunication technologies which allow two or more locations to interact via two-way video and audio transmissions simultaneously. It has also been called visual collaboration and is a type of groupware. It differs from videophone in that it is designed to serve a conference rather than individuals.

視像會議

video conferences