Videoconferencing 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 meeting activities, videoconferencing can be used to share documents, computer-displayed information, and whiteboards.
The core technology used in a videoconferencing 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 convert the digital pulses to/from analog waves in the audio spectrum range.
Hardware:
Ø Video input: video camera or webcam.
Ø Video output: computer monitor, television or projector.
Ø Audio input: microphones, CD/DVD player, cassette player, or any other source of Pre Amp audio outlet.
Ø Audio output: usually loudspeakers associated with the display device or telephone.
Ø Data transfer: analog or digital telephone network, LAN or Internet.
How it can be used:
Ø One-to-one meetings, also known as point to point communications, usually involving full two-way audio and video.
Ø One-to-many involving full audio and video broadcast from the main site, where other sites may be able to send audio. For example in a lecture situation, students could ask questions.
Ø Many-to-many, known as multi-point communication, provide audio and video between more than two sites. With most multi-point systems only one site in a conference can be seen at time, with switching between sites either controlled manually or voice activated (i.e., the loudest site is on screen).
Social impacts of the use of video conferencing:
Ø Eye Contact: It is known that eye contact plays a large role in conversational turn-taking, perceived attention and intent, and other aspects of group communication. While traditional telephone conversations give no eye contact cues, videoconferencing systems are arguably worse in that they provide an incorrect impression that the remote interlocutor is avoiding eye contact. Telepresence systems have cameras located in the screens that reduce the amount of parallax observed by the users. This issue is also being addressed through research that generates a synthetic image with eye contact using stereo reconstruction.
Bell Communications Research owns a patent for eye-to-eye video conferencing using rear projection screens with a camera behind it. This technique eliminates the need for special cameras or image processing.
Bell Communications Research owns a patent for eye-to-eye video conferencing using rear projection screens with a camera behind it. This technique eliminates the need for special cameras or image processing.
Ø Appearance Consciousness: A second problem with videoconferencing is being on camera, with the video stream possibly even being recorded. The burden of presenting an acceptable on-screen appearance is not present in audio-only communication. Early studies by Alphonse Chapanis found that the addition of video actually impaired communication, possibly because of the consciousness of being on camera.
Ø Signal latency: The information transport of digital signals in many steps needs time. In a telecommunicated conversation an increased latency, larger than about 150-300ms, becomes noticeable and soon unnatural and distracting. Therefore next to a stable large bandwidth, a small total round-trip time is another major technical requirement for the communication channel for interactive videoconferencing.
