Videoconferencing
From Wikipedia, the free encyclopedia
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.
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[edit] History
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.
Simple analog videoconferences could be established as early as the invention of the television. Such videoconferencing systems consisted of two closed-circuit television systems connected via cable. During the first manned space flights, NASA used two radiofrequency (UHF or VHF) links, one in each direction. TV channels routinely use this kind of videoconferencing when reporting from distant locations, for instance. Then mobile links to satellites using specially equipped trucks became rather common.
This technique was very expensive, though, and could not be used for more mundane applications, such as telemedicine, distance education, business meetings, and so on, particularly in long-distance applications. Attempts at using normal telephony networks to transmit slow-scan video, such as the first systems developed by AT&T, failed mostly due to the poor picture quality and the lack of efficient video compression techniques. The greater 1 MHz bandwidth and 6 Mbit/s bit rate of Picturephone in the 1970s also did not cause the service to prosper.
It was only in the 1980s that digital telephony transmission networks became possible, such as ISDN, assuring a minimum bit rate (usually 128 kilobits/s) for compressed video and audio transmission. The first dedicated systems, such as those manufactured by pioneering VTC firms, like PictureTel, started to appear in the market as ISDN networks were expanding throughout the world. Video teleconference systems throughout the 1990s rapidly evolved from highly expensive proprietary equipment, software and network requirements to standards based technology that is readily available to the general public at a reasonable cost. Finally, in the 1990s, IP (Internet Protocol) based videoconferencing became possible, and more efficient video compression technologies were developed, permitting desktop, or personal computer (PC)-based videoconferencing. In 1992 CU-SeeMe was developed at Cornell by Tim Dorcey et al., IVS was designed at INRIA, VTC arrived to the masses and free services, web plugins and software, such as NetMeeting, MSN Messenger, Yahoo Messenger, SightSpeed, Skype and others brought cheap, albeit low-quality, VTC.
[edit] Technology
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 1s and 0s 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 (manufactured by companies such as Sony, Tandberg, Polycom, and Radvision Ltd.) 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 PCs[1], 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.
[edit] Echo cancellation
A fundamental feature of professional VTC systems is acoustic echo cancellation (AEC). AEC is an algorithm which is able to detect when sounds or utterances reenter the audio input of the VTC codec, which came from the audio output of the same system, after some time delay. If unchecked, this can lead to several problems including 1) the remote party hearing their own voice coming back at them (usually significantly delayed) 2) strong reverberation, rendering the voice channel useless as it becomes hard to understand and 3) howling created by feedback. Echo cancellation is a processor-intensive task that usually works over a narrow range of sound delays.
[edit] Multipoint videoconferencing
Simultaneous videoconferencing among three or more remote points is possible by means of a Multipoint Control Unit (MCU). This is a bridge that interconnects calls from several sources (in a similar way to the audio conference call). All parties call the MCU unit, or the MCU unit can also call the parties which are going to participate, in sequence. There are MCU bridges for IP and ISDN-based videoconferencing. There are MCUs which are pure software, and others which are a combination of hardware and software. An MCU is characterised according to the number of simultaneous calls it can handle, its ability to conduct transposing of data rates and protocols, and features such as Continuous Presence, in which multiple parties can be seen onscreen at once.
MCUs can be stand-alone hardware devices, or they can be embedded into dedicated VTC units.
Some systems are capable of multipoint conferencing with no MCU, stand-alone, embedded or otherwise. These use a standards-based H.323 technique known as "decentralized multipoint", where each station in a multipoint call exchanges video and audio directly with the other stations with no central "manager" or other bottleneck. The advantages of this technique are that the video and audio will generally be of higher quality because they don't have to be relayed through a central point. Also, users can make ad-hoc multipoint calls without any concern for the availability or control of an MCU. This added convenience and quality comes at the expense of some increased network bandwidth, because every station must transmit to every other station directly.
[edit] Issues
Some observers [2] argue that two outstanding issues are preventing videoconferencing from becoming a standard form of communication, despite the ubiquity of videoconferencing-capable systems. These issues are:
- 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.[3] 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. This issue is being addressed through research that generates a synthetic image with eye contact using stereo reconstruction.[4]
- Appearance Consciousness: A second problem with videoconferencing is that one is literally 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.
The issue of eye-contact may be solved with advancing technology, and presumably the issue of appearance consciousness will fade as people become accustomed to videoconferencing.
[edit] Standards
The International Telecommunications Union (ITU) (formerly: Consultative Committee on International Telegraphy and Telephony (CCITT)) has three umbrellas of standards for VTC.
- ITU H.320 is known as the standard for public switched telephone networks (PSTN) or VTC over integrated services digital networks (ISDN) basic rate interface (BRI) or primary rate interface (PRI). H.320 is also used on dedicated networks such as T1 and satellite-based networks;
- ITU H.323 is known as a standard for transporting multimedia applications over LANs. This same standard also applies to older implementations of voice over IP VoIP. In recent years, the IETF's Session Initiation Protocol (SIP) has gained considerable momentum in practice for these two services.;
- ITU H.324 is the standard for transmission over POTS, or audio telephony networks. 3G-324M is a 3GPP implementation for video call on 3G mobile phones.
In recent years, IP based videoconferencing has emerged as a common communications interface and standard provided by VTC manufacturers in their traditional ISDN-based systems. Business, government and military organizations still predominantly use H.320 and ISDN VTC. Though, due to the price point and proliferation of the Internet, and broadband in particular, there has been a strong spurt of growth and use of H.323, IP VTC. H.323 has the advantage that it is accessible to anyone with a high speed Internet connection, such as DSL.
In addition, an attractive factor for IP VTC is that it is easier to set-up for use with a live VTC call along with web conferencing for use in data collaboration. These combined technologies enable users to have a much richer multimedia environment for live meetings, collaboration and presentations.
[edit] Impact on the general public
High speed Internet connectivity has become more widely available at a reasonable cost and the cost of video capture and display technology has decreased. Consequently personal video teleconference systems based on a webcam, personal computer system, software compression and broadband Internet connectivity have become affordable for the general public. Also, the hardware used for this technology has continued to improve in quality, and prices have dropped dramatically. The availability of freeware (often as part of chat programs) has made software based videoconferencing accessible to many.
For many years, futurists have envisioned a future where telephone conversations will take place as actual face-to-face encounters with video as well as audio. Sometimes it is simply not possible or practical to have a face-to-face meeting with two or more people. Sometimes a telephone conversation or conference call is adequate. Other times, an email exchange is adequate.
Videoconferencing adds another possible alternative, and can be considered when:
- a live conversation is needed;
- visual information is an important component of the conversation;
- the parties of the conversation can't physically come to the same location; or
- the expense or time of travel is a consideration.
Deaf and hard of hearing individuals have a particular interest in the development of affordable high-quality videoconferencing as a means of communicating with each other in sign language. Unlike Video Relay Service, which is intended to support communication between a caller using sign language and another party using spoken language, videoconferencing can be used between two signers.
Mass adoption and use of video conferencing is still relatively low, with the following often claimed as causes:
- Complexity of systems. Most users are not technical and want a simple interface. In hardware systems an unplugged cord or a flat battery in a remote control is seen as failure, contributing to perceived unreliability which drives users back to traditional meetings. Successful systems are backed by support teams who can pro-actively support and provide fast assistance when required.
- Perceived lack of interoperability: not all systems can readily interconnect, for example ISDN and IP systems require a bridge. Popular software solutions cannot easily connect to hardware systems. Some systems use different standards, features and qualities which can require additional configuration when connecting to dis-similar systems.
- Bandwidth and quality of service: In some countries it is difficult or expensive to get a high quality connection that is fast enough for good-quality video conferencing. Technologies such as ADSL have limited upload speeds and cannot upload and download simultaneously at full speed. As Internet speeds increase higher quality and high definition video conferencing will become more readily available.
- Expense of commercial systems - a well designed system requires a specially designed room and can cost hundreds of thousands of dollars to fit out the room with codecs, integration equipment and furniture.
For these reasons many hardware systems are often used for internal corporate use only, as they are less likely to run into problems and lose a sale. An alternative is companies that hire out video conferencing equipped meeting rooms in cities around the world. Customers simply book the rooms and turn up for the meeting - everything else is arranged and support is readily available if anything should go wrong.
[edit] Impact on education
- See also: Distance education
Videoconferencing provides students with the opportunity to learn by participating in a 2-way communication platform. Furthermore, teachers and lecturers from all over the world can be brought to classes in remote or otherwise isolated places. Students from diverse communities and backgrounds can come together to learn about one another. Students are able to explore, communicate, analyze and share information and ideas with one another. Through videoconferencing students can visit another part of the world to speak with others, visit a zoo, a museum and so on, to learn. These "virtual field trips" (see history of virtual learning environments) can bring opportunities to children, especially those in geographically isolated locations, or the economically disadvantaged. Small schools can use this technology to pool resources and teach courses (such as foreign languages) which could not otherwise be offered.
Here are a few examples of how videoconferencing can benefit people around campus:
- faculty member keeps in touch with class while away for a week at a conference
- guest lecturer brought into a class from another institution
- researcher collaborates with colleagues at other institutions on a regular basis without loss of time due to travel
- faculty member participates in a thesis defense at another institution
- administrators on tight schedules collaborate on a budget preparation from different parts of campus
- faculty committee auditions a scholarship candidate
- researcher answers questions about a grant proposal from an agency or review committee
- student interviews with an employer in another city
- Teleseminar
[edit] Impact on medicine and health
Videoconferencing is a very useful technology for telemedicine and telenursing applications, such as diagnosis, consulting, transmission of medical images, etc., in real time in countries where this is legal. Using VTC, patients may contact nurses and physicians in emergency or routine situations, physicians and other paramedical professionals can discuss cases across large distances. Rural areas can use this technology for diagnostic purposes, thus saving lives and making more efficient use of health care money.
Special peripherals such as microscopes fitted with digital cameras, videoendoscopes, medical ultrasound imaging devices, otoscopes, etc., can be used in conjunction with VTC equipment to transmit data about a patient.
[edit] Impact on business
Videoconferencing can enable individuals in faraway places to have meetings on short notice. Time and money that used to be spent in traveling can be used to have short meetings. Technology such as VOIP can be used in conjunction with desktop videoconferencing to enable low-cost face-to-face business meetings without leaving the desk, especially for businesses with wide-spread offices. The technology is also used for telecommuting, in which employees work from home.
Videoconferencing is now being introduced to online networking websites, in order to help businesses form profitable relationships quickly and efficiently without leaving their place of work.
Although it already has proven its potential value, research[5] has shown that many employees do not use the videoconference equipment because they are afraid that they will appear to be wasting time or looking for the easiest way if they use videoconferencing to enhance customer and supplier relationships. This anxiety can be avoided if managers use the technology in front of their employees.
[edit] Impact on law
Videoconferencing has allowed testimony to be used for individuals who are not able to attend the physical legal settings. In a military investigation in North Carolina, Afghan witnesses have testified using videoconferencing.
[edit] Landmarks
- 1995 First public videoconference and peacecast between continent of North America and Africa. Demonstration of telepresence, audience interaction, virtual dancing, etc. Linked a technofair in San Francisco with a techno-rave and cyberdeli in Cape Town.
- 1998 Winter Olympics opening ceremony in Nagano, Japan. Seiji Ozawa conducts the Ode to Joy from Beethoven's Ninth Symphony simultaneously across five continents in real time.
[edit] References
- ^ Using "Skype" for Desktop Video Conferences 2008, Skype Video-Conference Guide
- ^ Jim Van Meggelen 2005, The problem with video conferencing.
- ^ Vertegaal, "Explaining Effects of Eye Gaze on Mediated Group Conversations: Amount or Synchronization?" ACM Conference on Computer Supported Cooperative Work, 2002.).
- ^ Computer vision approaches to achieving eye contact appeared in the 1990s, such as Teleconferencing Eye Contact Using a Virtual Camera, ACM CHI 1993. More recently gaze correction systems using only a single camera have been shown, such as. Microsoft's GazeMaster system.
- ^ Wolfe, Mark. “Broadband videoconferencing as knowledge management tool,” Journal of Knowledge Management 11, no. 2 (2007)
[edit] See also
- Telepresence
- Teleconference
- Mobile VoIP
- Videophone for personal calls
