Modern Sign Language communication

Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio and video signals by people in different locations for real time communication.McGraw-Hill Concise Encyclopedia of Engineering
Videotelephony
McGraw-Hill, 2002. Retrieved from the FreeDictionary.com website, January 9, 2010 A videophone is a telephone with a video camera and video display, capable of simultaneous video and audio communication. Videoconferencing implies the use of this technology for a group or organizational meeting rather than for individuals, in a videoconference.Mulbach et al, 1995. pg. 291. Telepresence may refer either to a high-quality videotelephony system (where the goal is to create the illusion that remote participants are in the same room) or to meetup technology, which can go beyond video into robotics (such as moving around the room or physically manipulating objects). Videoconferencing has also been called "visual collaboration" and is a type of groupware.

While development of video-conferring started in the late 19th century, the technology only became available to the public starting in the 1930s. These early demonstrations were installed at "booths" in post offices and shown at various world expositions. It took until 1970 for AT&T to launch the first true video-conferring system, where anyone could subscribe to the service and have the technology in their home or office. Video-telephony also included "image phones" which would exchange still images between units every few seconds over conventional plain old telephone service (POTS) lines, essentially the same as slow-scan TV. The development of advanced video codecs, more powerful CPUs, and high-bandwidth Internet telecommunication services in the late 1990s allowed videophones to provide high quality low-cost colour service between users almost any place in the world where the Internet is available.

Although not as widely used in everyday communications as audio-only and text communication, useful applications include sign language transmission for deaf and speech-impaired people, distance education, telemedicine, and overcoming mobility issues. It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships. News media organisations have begun to use desktop technologies like Skype to provide higher-quality audio than the cellular phone network, and video links at much lower cost than sending professional equipment or using a professional studio. More popular videotelephony technologies use the Internet rather than the traditional landline phone network, even though modern phone networks use digital packet protocols, and videotelephony software commonly runs on smartphones over digital radiotelephony networks.

History

The concept of videotelephony was first conceived in the late 1870s, both in the United States and in Europe, although the basic sciences to permit its very earliest trials would take nearly a half century to be discovered. This was first embodied in the device which came to be known as the video telephone, or videophone, and it evolved from intensive research and experimentation in several telecommunication fields, notably electrical telegraphy, telephony, radio, and television.

Simple analog videophone communication could be established as early as the invention of the television. Such an antecedent usually consisted of two closed-circuit television systems connected via coax cable or radio. An example of that was the German Reich Postzentralamt (post office) videotelephone network serving Berlin and several German cities via coaxial cables between 1936 and 1940.

The development of videoconferencing as a subscription service started in the latter half of the 1920s in the United Kingdom and the United States, spurred notably by John Logie Baird and AT&T's Bell Labs. This occurred in part, at least with AT&T, to serve as an adjunct supplementing the use of the telephone. A number of organizations believed that videotelephony would be superior to plain voice communications. Attempts at using normal telephony networks to transmit slow-scan video, such as the first systems developed by AT&T Corporation, first researched in the 1950s, failed mostly due to the poor picture quality and the lack of efficient video compression techniques.

During the first crewed space flights, NASA used two radio-frequency ( UHF or VHF) video links, one in each direction. TV channels routinely use this type of videotelephony when reporting from distant locations. The news media were to become regular users of mobile links to satellites using specially equipped trucks, and much later via special satellite videophones in a briefcase. This technique was very expensive, though, and could not be used for applications such as telemedicine, distance education, and business meetings.

Decades of research and development culminated in the 1970 commercial launch of AT&T's Picturephone service, available in select cities. However, the system was a commercial failure, chiefly due to consumer apathy, high subscription costs, and lack of network effect—with only a few hundred Picturephones in the world, users had extremely few contacts they could actually call, and interoperability with other videophone systems would not exist for decades.

Very expensive videoconferencing systems continued to evolve throughout the 1980s and 1990s. Proprietary equipment, software, and network requirements gave way to standards-based technologies that were available for anyone to purchase at a reasonable cost. Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN service did videotelephony become a practical technology for regular use.

Digital

Advances in video compression allowed digital video streams to be transmitted over the Internet, which was previously difficult due to the impractically high bandwidth requirements of uncompressed video. To achieve Video Graphics Array (VGA) quality video (480p resolution and 256 colors) with raw uncompressed video, it would require a bandwidth of over 92Mbps. A common compression technique used to significantly reduce bandwidth requirements in videotelephony and videoconferencing is the discrete cosine transform (DCT), developed by Nasir Ahmed, T. Natarajan and K. R. Rao in 1973. The DCT algorithm was the basis for the first practical video coding standard that was useful for online videoconferencing, H.261, standardised by the ITU-T in 1988, and subsequent H.26x video coding standards.

In the 1980s, digital telephony transmission networks became possible, such as with ISDN networks, assuring a minimum bit rate (usually 128 kilobits/s) for compressed video and audio transmission. During this time, there was also research into other forms of digital video and audio communication. Many of these technologies, such as the Media space, are not as widely used today as videoconferencing but were still an important area of research. The first dedicated systems started to appear as ISDN networks were expanding throughout the world. One of the first commercial videoconferencing systems sold to companies came from PictureTel Corp., which had an initial public offering in November, 1984.

In 1984, Concept Communication in the United States replaced the , US$100,000 computers necessary for teleconferencing, with a $12,000 circuit board that doubled the video frame rate from 15 to 30 frames per second, and which reduced the equipment to the size of a circuit board fitting into standard personal computers. The company also secured a patent for a codec for full-motion videoconferencing, first demonstrated at AT&T Bell Labs in 1986.

Videoconferencing systems throughout the 1990s rapidly evolved from very expensive proprietary equipment, software, and network requirements to a standards-based technology readily available to the general public at a reasonable cost.

Finally, in the 1990s, 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. In 1995 the first public videoconference between North America and Africa took place, linking a technofair in San Francisco with a techno-rave and cyberdeli in Cape Town. At the 1998 Winter Olympics opening ceremony in Nagano, Japan, Seiji Ozawa conducted the Ode to Joy from Beethoven's Ninth Symphony simultaneously across five continents in near-real-time.

While videoconferencing technology was initially used primarily within internal corporate communication networks, one of the first community service uses of the technology started in 1992 through a unique partnership with PictureTel and IBM, which at the time were promoting a jointly developed desktop based videoconferencing product known as the PCS/1. Over the next 15 years, Project DIANE (Diversified Information and Assistance Network) grew to use a variety of videoconferencing platforms to create a multi-state cooperative public service and distance education network consisting of several hundred schools, libraries, science museums, zoos and parks, and many other community oriented organizations.

Kyocera conducted a two-year development campaign from 1997 to 1999 that resulted in the release of the VP-210 Visual Phone, the first mobile colour videophone that also doubled as a camera phone for still photos.Kyocera visual phone VP-210, Japan, 1999
Science & Society Picture Library, retrieved August 9, 2013.First mobile videophone introduced
CNN.com website, May 18, 1999. The camera phone was the same size as similar contemporary mobile phones, but sported a large camera lens and a 5 cm (2 inch) colour TFT display capable of displaying 65,000 colors, and was able to process two video frames per second.Yegulalp, Serdar
Camera phones: A look back and forward
'' Computerworld'', May 11, 2012.

Videotelephony was popularized in the 2000s, via free Internet services such as Skype and iChat, web plugins supporting H.26x video standards, and on-line telecommunication programs that promoted low cost, albeit lower quality, videoconferencing to virtually every location with an Internet connection.

With the rapid improvements and popularity of the Internet, videotelephony has become widespread through the deployment of video-enabled mobile phones such as 2010's iPhone 4, plus videoconferencing and computer webcams which use Internet telephony. In the upper echelons of government, business, and commerce, telepresence technology, an advanced form of videoconferencing, has helped reduce the need to travel.

In May 2005, the first high definition videoconferencing systems, produced by LifeSize Communications, were displayed at the Interop trade show in Las Vegas, Nevada, able to provide video at 30 frames per second with a 1280 by 720 display resolution. Polycom introduced its first high definition videoconferencing system to the market in 2006. As of the 2010s, high definition resolution for videoconferencing became a popular feature, with most major suppliers in the videoconferencing market offering it.

Technological developments by videoconferencing developers in the 2010s have extended the capabilities of videoconferencing systems beyond the boardroom for use with hand-held mobile devices that combine the use of video, audio and on-screen drawing capabilities broadcasting in real time over secure networks, independent of location. Mobile collaboration systems now allow people in previously unreachable locations, such as workers on an offshore oil rig, the ability to view and discuss issues with colleagues thousands of miles away. Traditional videoconferencing system manufacturers have begun providing mobile applications as well, such as those that allow for live and still image streaming.

The highest ever video call (other than those from aircraft and spacecraft) took place on May 19, 2013, when British adventurer Daniel Hughes used a smartphone with a BGAN satellite modem to make a videocall to the BBC
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