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. Conducting a conference between two or more participants at different sites by using computer networks to transmit audio and video data. For example, a point-to-point (two-person) video conferencing system works much like a video telephone. Each participant has a video camera, microphone, and speakers mounted on his or her computer. As the two participants speak to one another, their voices are carried over the network and delivered to the other's speakers, and whatever images appear in front of the video camera appear in a window on the other participant's monitor.
Multipoint videoconferencing allows three or more participants to sit in a virtual conference room and communicate as if they were sitting right next to each other. Until the mid 90s, the hardware costs made videoconferencing prohibitively expensive for most organizations, but that situation is changing rapidly. Many analysts believe that videoconferencing will be one of the fastest-growing segments of the computer industry in the latter half of the decade.
A videoconference in progress using a dedicated device (Aethra) via ISDN and a computer for data interchange support
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 special trucks became rather common.
Videoconferencing first demonstrated in 1968
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. It was only in the 1980s that digital telephony transmission networks became possible, such as ISDN, assuring a minimum bandwidth (usually 128 kilobits/sec) 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 1990's 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. VTC arrived to the masses and free services and software, such as NetMeeting, MSN Messenger, Yahoo Messenger, and others brought cheap, albeit low-quality, VTC.
Dedicated videoconferencing system with two TV displays, one for the videoconferencing, another for the slide presentation. The VTC console sits on the top of the TV at left and includes a PTZ camera
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 or television
• 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:
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. 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:
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 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.
A fundamental feature of professional VTC systems is acoustic echo cancellation (AEC). AEC is an algorithm which is able to detect when sounds or utterences 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.
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, it's 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.
Some observers  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:
1. 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. This issue is being addressed though research that generates a synthetic image with eye contact using stereo reconstruction  .
2. 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.
The International Telecommunications Union (ITU) (formerly: Consultative Committee on International Telegraphy and Telephony (CCITT)) has three umbrellas of standards for VTC.
1. ITU H.320
2. ITU H.323
3. ITU H.324.
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 free software (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. Desktop PC videoconferencing promises to make this a reality, although it remains to be seen whether there is widespread enthusiasm for video calling.
Impact on 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 video conferencing 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" can bring opportunities to children, especially those in geographically isolated or the economically disadvantaged. Small schools can use this technology to pool resources and teach courses (such as foreign languages) which otherwise couldn't be offered. Teachers can use this technology to acquire additional college credits for recertification without driving to classes.
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. Using VTC, patients may contact nurses and physicians in medical 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 dollars.
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.
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 face-to-face business meetings without leaving the desktop.
Meetings are an important part of the job in Extension. This is because face-to-face (FTF) interaction is the traditional standard on which we base our communication with clientele groups, advisory boards, and Extension colleagues. However, FTF meetings may be an inefficient and costly way to conduct business, particularly when participants must travel a great distance. Over the past few years, travel-related costs (lodging, airfare, meals), have increased at a rate frequently greater than that of inflation.1 Travel budgets, on the other hand, have often remained static or decreased. An alternative meeting format called teleconferencing may be a solution.
...teleconferencing can only facilitate the linking of people-it does not alter the complexity of group communication. Although it may be easier for us to communicate with teleconferencing, it may also be easier for us to miscommunicate.
Teleconferencing is interactive group communication (three or more people in two or more locations) through an electronic medium.2 In general terms, teleconferencing can bring people together under one roof even though they're separated by hundreds of miles. Teleconferencing was first introduced in the 1960's with American Telephone and Telegraph's Picturephone. At that time, however, no demand existed for the new technology. Travel costs were reasonable and consumers were unwilling to pay the monthly service charge for using the picturephone, which was regarded as more of a novelty than as an actual means for everyday communication. But things have changed in the past 10 years.
Today, teleconferencing is used in many ways. There are three basic types:
• Video conferencing-television-like communication augmented with sound.
• Computer conferencing-printed communication through keyboard terminals.
• Audio-conferencing -verbal communication via the telephone with optional capacity for telewriting or telecopying.3
In some state Extension programs (Wisconsin and Illinois), teleconferencing is a basic communication technique. Yet, the verdict is still out in many other states. This article highlights some of the major advantages and disadvantages of teleconferencing and answers some questions for those uncertain about using teleconferencing in their Extension activities.
One of the major advantages of teleconferencing is its potential to reduce the cost of group meetings. Savings come primarily from reduced travel costs. In fact, teleconferencing can reduce national business travel-associated costs by about 30% annually-a $4.5 billion savings. 4 A good example of the dollars that can be saved is a teleconference conducted by the Spruce Budworm Technology Transfer (SBWTT) Program for the Lake States Region-part of the Canada/United States Spruce Budworm Program.
The SBWTT project is a forest entomology research effort concerned with disseminating information about the spruce budworm to forest managers in Michigan, Minnesota, and Wisconsin. Part of the project involved a cost comparison between a 14-person audioconference and a comparable FTF meeting in St. Paul, Minnesota. The comparison revealed that the audioconference cost 42% less that the FTF meeting.5 The major difference between the two was the travel-related expenses.
Although saving money is a big advantage of teleconferencing, there are several other advantages:
• People (including outside guest speakers) who wouldn't normally attend a distant FTF meeting can participate.
• Follow-up to earlier meetings can be done with relative ease and little expense.
• Socializing is minimal compared to an FTF meeting; therefore, meetings are shorter and more oriented to the primary purpose of the meeting.
• Some routine meetings are more effective since one can audioconference from any location equipped with a telephone.
• Communication between the home office and field staffs is maximized.
• Severe climate and/or unreliable transportation may necessitate teleconferencing.
• Participants are generally better prepared than for FTF meetings.
• It's particularly satisfactory for simple problem solving, information exchange, and procedural tasks.
• Group members participate more equally in wellmoderated teleconferences than in an FTF meeting.6
While teleconferencing is characterized by many advantages, it does have disadvantages:
• Technical failures with equipment, including connections that aren't made.
• Unsatisfactory for complex interpersonal communication, such as negotiation or bargaining.
• Impersonal, less easy to create an atmosphere of group rapport.
• Lack of participant familiarity with the equipment, the medium itself, and meeting skills.
• Acoustical problems within the teleconferencing rooms.
• Difficulty in determining participant speaking order; frequently one person monopolizes the meeting.
• Greater participant preparation and preparation time needed.
• Informal, one-to-one, social interaction not possible.7
To minimize some of the potential problems, users should carefully evaluate their meeting needs and goals to determine if teleconferencing is appropriate. Users should also assess their audience. For example, consider the size of the group, their level of experience with teleconferencing, and the extent of their familiarity with each other. These precautions won't eliminate all the problems that could arise, but they should reduce the likelihood of their occurring.
Teleconferencing represents a unique alternative to the traditional FTF meeting. Most of the time, a teleconference is an appropriate substitute. Every meeting is unique, with different goals, objectives, and purpose. Teleconferencing can't satisfy the individual needs of every type of meeting. Teleconferencing and FTF meetings involve different patterns of interaction and social codes of behavior. As we develop and refine new communication patterns appropriate for teleconferencing, we'll be modifying future human communication patterns. Researchers at the Institute for the Future in Menlo Park, California, offer some suggestions as we make this transition:
1. The system isn't the solution. The technology of teleconferencing has been emphasized -often at the expense of social and organizational structures that support communication. The medium of communication is only the means to carry information; the end to which the medium is used also must be considered.
2. Face-to-face interaction isn't always the best, although it's generally the standard to which media designers aspire. However, anyone who has been forced to sit through a boring meeting can attest to the fact that an FTF meeting is often both inefficient and ineffective.
3. More communication isn't always better. Consideration of teleconferencing media is often accompanied by an unexamined assumption that more communication would most certainly be better. Often, people have more information than they're able to absorb effectively, and introducing yet another means of communication could make things worse. Communication pollution and information overload are real problems.8
Teleconferencing has vast potential for increasing the efficiency of human communication. For those of us in Extension, this means less time away from home, more money to devote to other activities, and more time to spend on other projects. Yet, teleconferencing for all it's worth can never totally replace FTF meetings. FTF interaction is an important part of human communication. Furthermore, teleconferencing can only facilitate the linking of people-it does not alter the complexity of group communication. Although it may be easier for us to communicate with teleconferencing, it may also be easier for us to miscommunicate.