Videotelephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time.[1]
At the dawn of the technology, videotelephony also included image phones which would exchange still images between units every few seconds over conventional POTS-type telephone lines, essentially the same as slow scan TV systems.
Currently videotelephony usage has made significant inroads in government, healthcare, education and the news media. It is particularly useful to the deaf and speech-impaired who can use them with sign language and also with a video relay service, and well as to those with mobility issues or those who are located in distant places and are in need of telemedical or tele-educational services.
It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships.
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The concept of videotelephony was first popularized in the late 1880s in both the United States and Europe, although the sciences to permit its very earliest trials would take nearly a half century to be discovered. These evolved from studies and experimentation in the fields of electrical telegraphy, telephony, radio and television.
The development of video and television transmission technologies in the United States and the United Kingdom started in the latter half of the 1920s, spurred notably by AT&T, occurred in part to serve as an adjunct to the use of the telephone. A number of organizations believed that videotelephony would be superior to plain voice telecommunication. However video technology was to be deployed in analog television broadcasting long before it could become practical in videotelephony.
Videotelephony can be categorized by its functionality, that is to its intended purpose, and also by its method of transmissions.
Videophones were the earliest form of videotelephony, dating back to initial tests in 1927 by AT&T. During the late 1930s the post offices of several European governments established public videophone services for person-to-person communications utilizing dual cable circuit telephone transmission technology. In the present day standalone videophones and UMTS video-enabled mobile phones are usually used on a person-to-person basis.
Videoconferencing saw its earliest use with AT&T's Picturephone service in the early 1970s. Transmissions were analog over short distances, but converted to digital forms for longer calls, again using telephone transmission technology. Popular corporate videoconferencing systems in the present day have migrated almost exclusively to digital ISDN and IP transmission modes due to the need to convey the very large amounts of data generated by their cameras and microphones. These systems are often intended for use in conference mode, that is by many people in several different locations, all of whom can be viewed by every participant at each location.
Telepresence systems are a newer, more advanced subset of videoconferencing systems, meant to allow higher degrees of video and audio fidelity. Such high end systems are typically deployed in corporate settings.
Mobile collaboration systems are another recent development, combining the use of video, audio, and on-screen drawing capabilities using newest generation hand-held electronic devices broadcasting over secure networks, enabling multi-party conferencing in real-time, independent of location.
Personal computer based web cameras are an often modest form of videotelephony, usually used for point-to-point videophone calls.
Each of the systems has its own advantages and disadvantages, including video quality, capital cost, degrees of sophistication, transmission capacity requirements, and cost of use.
From the least to the most expensive systems:
One of the first demonstrations of the ability for telecommunications to help sign language users communicate with each other occurred when AT&T's videophone (trademarked as the "Picturephone") was introduced to the public at the 1964 New York World's Fair –two deaf users were able to communicate freely with each other between the fair and another city.[2] Various other organizations, including British Telecom's Martlesham facility and several universities have also conducted extensive research on signing via videotelephony.[3] The use of sign language via videotelephony was hampered for many years due to the difficulty of its use over slow analogue copper phone lines coupled with the high cost of better quality ISDN (data) phone lines.[3] Those factors largely disappeared with the introduction of more efficient video codecs and the advent of lower cost high-speed ISDN data and IP (Internet) services in the 1990s.
Significant improvements in video call quality of service for the deaf occurred in the United States in 2003 when Sorenson Media Inc. (formerly Sorenson Vision Inc.), a video compression software coding company, developed its VP-100 model stand-alone videophone specifically for the deaf community. It was designed to output its video to the user's television in order to lower the cost of acquisition, and to offer remote control and a powerful video compression codec for unequaled video quality and ease of use with video relay services. Favourable reviews quickly led to its popular usage at educational facilities for the deaf, and from there to the greater deaf community.[4]
Coupled with similar high-quality videophones introduced by other electronics manufacturers, the availability of high speed Internet, and sponsored video relay services authorized by the U.S. Federal Communications Commission in 2002, VRS services for the deaf underwent rapid growth in that country.[4]
Using such video equipment in the present day, the deaf, hard-of-hearing and speech-impaired can communicate between themselves and with hearing individuals using sign language. The United States and several other countries compensate companies to provide 'Video Relay Services' (VRS). Telecommunication equipment can be used to talk to others via a sign language interpreter, who uses a conventional telephone at the same time to communicate with the deaf person's party. Video equipment is also used to do on-site sign language translation via Video Remote Interpreting (VRI). The relative low cost and widespread availability of 3G mobile phone technology with video calling capabilities have given deaf and speech-impaired users a greater ability to communicate with the same ease as others. Some wireless operators have even started free sign language gateways.
Sign language interpretation services via VRS or by VRI are useful in the present-day where one of the parties is deaf, hard-of-hearing or speech-impaired (mute). In such cases the interpretation flow is normally within the same principal language, such as French Sign Language (LSF) to spoken French, Spanish Sign Language (LSE) to spoken Spanish, British Sign Language (BSL) to spoken English, and American Sign Language (ASL) also to spoken English (since BSL and ASL are completely distinct to each other), and so on.
Multilingual sign language interpreters, who can also translate as well across principal languages (such as to and from SSL, to and from spoken English), are also available, albeit less frequently. Such activities involve considerable effort on the part of the translator, since sign languages are distinct natural languages with their own construction, semantics and syntax, different from the aural version of the same principal language.
With video interpreting, sign language interpreters work remotely with live video and audio feeds, so that the interpreter can see the deaf or mute party, and converse with the hearing party, and vice versa. Much like telephone interpreting, video interpreting can be used for situations in which no on-site interpreters are available. However, video interpreting cannot be used for situations in which all parties are speaking via telephone alone. VRS and VRI interpretation requires all parties to have the necessary equipment. Some advanced equipment enables interpreters to control the video camera remotely, in order to zoom in and out or to point the camera toward the party that is signing.
Videophone calls (also: videocalls and video chat),[5] differ from videoconferencing in that they expect to serve individuals, not groups.[6] However that distinction has become increasingly blurred with technology improvements such as increased bandwidth and sophisticated software clients that can allow for multiple parties on a call. In general everyday usage the term videoconferencing is now frequently used instead of videocall for point-to-point calls between two units. Both videophone calls and videoconferencing are also now commonly referred to as a video link.
Webcams are popular, relatively low cost devices which can provide live video and audio streams via personal computers, and can be used with many software clients for both video calls and videoconferencing.[7]
A videoconference system is generally higher cost than a videophone and deploys greater capabilities. A videoconference (also known as a videoteleconference) allows two or more locations to communicate via live, simultaneous two-way video and audio transmissions. This is often accomplished by the use of a multipoint control unit (a centralized distribution and call management system) or by a similar non-centralized multipoint capability embedded in each videoconferencing unit. Again, technology improvements have circumvented traditional definitions by allowing multiple party videoconferencing via web-based applications.[8][9] A separate webpage article is devoted to videoconferencing.
A telepresence system is a high-end videoconferencing system and service usually employed by enterprise-level corporate offices. Telepresence conference rooms use state-of-the art room designs, video cameras, displays, sound-systems and processors, coupled with high-to-very-high capacity bandwidth transmissions.
Typical uses of the various technologies described above include videocalling or videoconferencing on a one-to-one, one-to-many or many-to-many basis for personal, business, educational, deaf Video Relay Service and tele-medical, diagnostic and rehabilitative use or services. New services utilizing videocalling and videoconferencing, such as personal videocalls to inmates incarcerated in penitentiaries, and videoconferencing to resolve airline engineering issues at maintenance facilities, are being created or evolving on an on-going basis.
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