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'''Videotelephony''' (also known as '''videoconferencing''', '''video teleconferencing''', or simply '''video call''') is the two-way or multipoint reception and transmission of [[:en:Audio_signal|audio]] and [[:en:Video|video]] signals by people in different locations for [[:en:Real-time|real-time]] communication.<ref name="McGrawHill">McGraw-Hill Concise Encyclopedia of Engineering. [http://encyclopedia2.thefreedictionary.com/Videotelephony Videotelephony], McGraw-Hill, 2002. Retrieved from the FreeDictionary.com website, January 9, 2010</ref> A videophone is a [[:en:Telephone|telephone]] with a [[:en:Video_camera|video camera]] and [[:en:Display_device|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.<ref name="Mulbach-1995c">Mulbach et al, 1995. pg. 291.</ref> [[:en:Telepresence|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 [[:en:Groupware|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. Videotelephony also included ''image phones'' which would exchange still images between units every few seconds over conventional [[:en:Plain_old_telephone_service|plain old telephone service]] (POTS) lines, essentially the same as [[:en:Slow-scan_television|slow-scan TV]]. The development of advanced [[:en:Codec|video codecs]], more powerful [[:en:CPU|CPUs]], and high-bandwidth [[:en:Internet_service|Internet service]] in the late 1990s allowed videophones to provide high-quality low-cost color service between users almost any place in the world where the [[:en:Internet|Internet]] is available.
Useful applications include [[:en:Sign_language|sign language]] transmission for [[:en:Deaf|deaf]] and [[:en:Speech_disorder|speech-impaired]] people, [[:en:Distance_education|distance education]], [[:en:Telemedicine|telemedicine]], and overcoming [[:en:Disability|mobility issues]]. It is also used in commercial and corporate settings to facilitate meetings and conferences. [[:en:News_media|News media]] organizations have begun to use desktop technologies like [[:en:Skype|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.{{Citation needed|date=April 2020}} 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 [[:en:Smartphone|smartphones]] over digital radiotelephony networks.
==
{{Main|History of videotelephony}}
[[File:France_in_XXI_Century._Correspondance_cinema.jpg|link=https://en.wikipedia.org/wiki/File:France_in_XXI_Century._Correspondance_cinema.jpg|thumb|Videotelephony predicted to be in use by 2000, as envisioned in 1910 (artist's conception)]]
[[File:Bell_telephone_magazine_(1922)_(14756466975).jpg|link=https://en.wikipedia.org/wiki/File:Bell_telephone_magazine_(1922)_(14756466975).jpg|thumb|Videotelephone booth, 1922]]
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.{{citation needed|date=February 2018}} 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 [[:en:Electrical_telegraphy|electrical telegraphy]], [[:en:Telephony|telephony]], [[:en:Radio|radio]], and [[:en:Television|television]].
Simple analog videophone communication could be established as early as the invention of the [[:en:Television|television]]. Such an antecedent usually consisted of two [[:en:Closed-circuit_television|closed-circuit television]] systems connected via [[:en:Coaxial_cable|coax cable]] or [[:en:Radio|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.<ref>"German Postoffice To Use Television–Telephone For Its Communication System", (Associated Press) The Evening Independent, St. Petersburg, Fl, September 1, 1934</ref><ref>Peters, C. Brooks, "Talks On 'See-Phone': Television Applied to German Telephones Enables Speakers to See Each Other{{nbsp}}...", The New York Times, September 18, 1938</ref>
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 [[:en:John_Logie_Baird|John Logie Baird]] and [[:en:Bell_Labs|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 [[:en:Telephony|telephony]] networks to transmit slow-scan video, such as the first systems developed by [[:en:AT&T_Corporation|AT&T Corporation]], first researched in the 1950s, failed mostly due to the poor picture quality and the lack of efficient [[:en:Video_compression|video compression]] techniques.
During the first crewed [[:en:Space_flight|space flights]], [[:en:NASA|NASA]] used two radio-frequency ([[:en:UHF|UHF]] or [[:en:VHF|VHF]]) video links, one in each direction. [[:en:Television|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 [[:en:Satellite|satellites]] using specially equipped trucks, and much later via special satellite videophones in a briefcase. This technique was very expensive, though, and was not adopted for applications such as [[:en:Telemedicine|telemedicine]], [[:en:Distance_education|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 [[:en:Network_effect|network effect]]—with only a few hundred Picturephones in the world, users had extremely few contacts they could actually call, and [[:en:Interoperability|interoperability]] with other videophone systems would not exist for decades.
=== Əsərləri ===
[[File:On_Line_System_Videoconferencing_FJCC_1968.jpg|link=https://en.wikipedia.org/wiki/File:On_Line_System_Videoconferencing_FJCC_1968.jpg|thumb|Multiple user videoconferencing first being demonstrated with [[:en:Stanford_Research_Institute|Stanford Research Institute]]'s [[:en:NLS_(computer_system)|NLS computer technology]] (1968)]]
[[File:1969_AT&T_Picturephone_Model_2_at_the_Early_Television_Museum_June_2022.jpg|link=https://en.wikipedia.org/wiki/File:1969_AT&T_Picturephone_Model_2_at_the_Early_Television_Museum_June_2022.jpg|thumb|An AT&T Picturephone Model 2 from 1969]]
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 [[:en:Video_codec|video codecs]] combined with high-speed [[:en:Internet_access|Internet broadband]] and [[:en:Integrated_Services_Digital_Network|ISDN]] service did videotelephony become a practical technology for regular use.
===
Advances in [[:en:Video_compression|video compression]] allowed [[:en:Digital_video|digital video]] streams to be transmitted over the Internet, which was previously difficult due to the impractically high bandwidth requirements of [[:en:Uncompressed_video|uncompressed video]]. To achieve [[:en:Video_Graphics_Array|Video Graphics Array]] (VGA) quality video without compression, it would require a bandwidth of over 92{{nbsp}}[[:en:Mbps|Mbps]].<ref name="Belmudez">{{cite book |last1=Belmudez |first1=Benjamin |url=https://archive.org/details/audiovisualquali0000unse/page/10/mode/2up |title=Audiovisual Quality Assessment and Prediction for Videotelephony |date=2014 |publisher=Springer |isbn=9783319141664 |pages=11–13}}</ref> A common compression technique used to significantly reduce bandwidth requirements in videotelephony and videoconferencing is the [[:en:Discrete_cosine_transform|discrete cosine transform]] (DCT),<ref name="Belmudez" /><ref name="Huang">{{cite book |last1=Huang |first1=Hsiang-Cheh |url=https://books.google.com/books?id=67W5BQAAQBAJ&pg=PA41 |title=Intelligent Multimedia Data Hiding: New Directions |last2=Fang |first2=Wai-Chi |date=2007 |publisher=Springer |isbn=9783540711698 |page=41}}</ref> developed by [[:en:Nasir_Ahmed_(engineer)|Nasir Ahmed]], T. Natarajan and [[:en:K._R._Rao|K. R. Rao]] in 1973.<ref name="Ahmed">{{cite journal|last=Ahmed|first=Nasir|author-link=N. Ahmed|title=How I Came Up With the Discrete Cosine Transform|journal=[[Digital Signal Processing (journal)|Digital Signal Processing]]|date=January 1991|volume=1|issue=1|pages=4–5|doi=10.1016/1051-2004(91)90086-Z|url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform}}</ref> The DCT algorithm was the basis for the first practical [[:en:Video_coding_standard|video coding standard]] that was useful for online videoconferencing, [[:en:H.261|H.261]], standardised by the [[:en:ITU-T|ITU-T]] in 1988, and subsequent [[:en:H.26x|H.26x]] [[:en:Video_coding_standard|video coding standards]].<ref name="Huang" />
In the 1980s, [[:en:Digital_telephony|digital telephony]] transmission networks became possible, such as with [[:en:Integrated_Services_Digital_Network|ISDN]] networks, assuring a minimum [[:en:Bit_rate|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 [[:en:Media_space|Media space]], are not as widely used today as videoconferencing but were still an important area of research.<ref>Robert Stults, Media Space, Xerox PARC, Palo Alto, CA, 1986.</ref><ref>Harrison, Steve. [https://books.google.com/books?id=xIujg_rkEX8C Media Space: 20+ Years of Mediated Life] {{webarchive|url=https://web.archive.org/web/20160505084733/https://books.google.com/books?id=xIujg_rkEX8C|date=2016-05-05}}, Springer, 2009, {{ISBN|1-84882-482-3}}, {{ISBN|978-1-84882-482-9}}.</ref> 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 [[:en:PictureTel_Corp.|PictureTel Corp.]], which had an [[:en:Initial_public_offering|initial public offering]] in November, 1984.
In 1984, Concept Communication in the United States replaced the {{convert|100|lb|adj=on}}, US$100,000 computers necessary for teleconferencing, with a $12,000 [[:en:Circuit_board|circuit board]] that doubled the video [[:en:Frame_rate|frame rate]] from 15 to 30 frames per second, and which reduced the equipment to the size of a circuit board fitting into standard [[:en:Personal_computer|personal computers]].<ref name="williamjtobin">{{cite news |title=Mr. Tobin has been awarded 15 patents in the past 40 years |publisher=WilliamJTobin.com |url=http://www.williamjtobin.com/inventions--patents.html |url-status=live |access-date=2011-05-18 |archive-url=https://web.archive.org/web/20110530033905/http://www.williamjtobin.com/inventions--patents.html |archive-date=2011-05-30}}</ref> The company also secured a patent for a [[:en:Codec|codec]] for full-motion videoconferencing, first demonstrated at [[:en:AT&T_Bell_Labs|AT&T Bell Labs]] in 1986.<ref name="williamjtobin" /><ref name="rtir">{{cite news |date=April 1, 2011 |title=Entrepreneur of the Year Reveals Secrets to His Success |work=RTIR (Radio TV Interview Report) |url=http://www.rtironline.com/blog/_archives/2011/4/1/4801142.html |access-date=2011-05-18 |archive-url=https://web.archive.org/web/20110724155651/http://www.rtironline.com/2011/04/01/entrepeneur-of-the-year-reveals-secrets-to-his-success/ |archive-date=2011-07-24}}</ref>
[[File:CUcollaboration.gif|link=https://en.wikipedia.org/wiki/File:CUcollaboration.gif|right|thumb|Global Schoolhouse students communicating via [[:en:CU-SeeMe|CU-SeeMe]], shown here with a video [[:en:Frame_rate|frame rate]] between 0.9 and 3 frames per second (1993)]]
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, [[:en:Internet_Protocol|Internet Protocol]]-based videoconferencing became possible, and more efficient video compression technologies were developed, permitting desktop, or personal computer (PC)-based videoconferencing. In 1992 [[:en:CU-SeeMe|CU-SeeMe]] was developed at Cornell by Tim Dorcey et al. In 1995 the [[:en:South_African_Communication_Landmarks#Telecommunication_landmarks|first public videoconference between North America and Africa]] took place, linking a technofair in [[:en:San_Francisco|San Francisco]] with a techno-rave and cyberdeli in [[:en:Cape_Town|Cape Town]]. At the [[:en:1998_Winter_Olympics|1998 Winter Olympics]] opening ceremony in [[:en:Nagano,_Nagano|Nagano]], Japan, [[:en:Seiji_Ozawa|Seiji Ozawa]] conducted the [[:en:Ode_to_Joy|Ode to Joy]] from [[:en:Beethoven's_Ninth_Symphony|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, [[:en:Project_DIANE|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.
[[File:Kyocera_VP-210_CP+_2011.jpg|link=https://en.wikipedia.org/wiki/File:Kyocera_VP-210_CP+_2011.jpg|right|thumb|The [[:en:Kyocera|Kyocera]] VP-210 Visual Phone was the first commercial mobile videophone (1999).]]
[[:en:Kyocera|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 [[:en:Camera_phone|camera phone]] for still photos.<ref name="S&S">[http://www.scienceandsociety.co.uk/results.asp?image=10321681&screenwidth=1366 Kyocera visual phone VP-210, Japan, 1999], Science & Society Picture Library, retrieved August 9, 2013.</ref><ref name="CNN-1999.05.18">[http://www.cnn.com/TECH/ptech/9905/18/japan.phonetv/ First mobile videophone introduced], [[CNN]].com website, May 18, 1999.</ref> The camera phone was the same size as similar contemporary [[:en:Mobile_phone|mobile phones]], but sported a large camera lens and a 5 cm (2 inch) colour [[:en:Thin-film-transistor_liquid-crystal_display|TFT display]] capable of displaying 65,000 colors, and was able to process two video frames per second.<ref name="CNN-1999.05.18" /><ref name="Computerworld-2012.05.11">Yegulalp, Serdar. [http://www.computerworld.com/slideshow/detail/45496 Camera phones: A look back and forward] {{Webarchive|url=https://web.archive.org/web/20140704121339/http://www.computerworld.com/slideshow/detail/45496|date=2014-07-04}}, ''[[Computerworld]]'', May 11, 2012.</ref>
Videotelephony was popularized in the 2000s, via free Internet services such as [[:en:Skype|Skype]] and [[:en:IChat|iChat]], web plugins supporting [[:en:H.26x|H.26x]] video standards, and online 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 [[:en:Mobile_phone|mobile phones]] such as 2010s [[:en:IPhone_4|iPhone 4]], plus videoconferencing and [[:en:Webcam|computer webcams]] which use [[:en:Voice_over_IP|Internet telephony]]. In the upper echelons of government, business, and commerce, [[:en:Telepresence|telepresence technology]], an advanced form of videoconferencing, has helped reduce the need to travel.{{citation needed|date=March 2017}}
* {{wikisource author-inline|Fuzuli}}{{commons-inline}}{{Azərbaycan ədəbiyyatı}}{{Authority control}}
In May 2005, the first [[:en:High-definition_video|high definition]] videoconferencing systems, produced by [[:en:Lifesize_communications|LifeSize Communications]], were displayed at the [[:en:Interop|Interop]] trade show in [[:en:Las_Vegas_Valley|Las Vegas]], [[:en:Nevada|Nevada]], able to provide video at 30 frames per second with a 1280 by 720 [[:en:Display_resolution|display resolution]].<ref>{{cite web |author=George Ou |title=High definition videoconferencing is here |url=http://www.zdnet.com/blog/ou/high-definition-video-conferencing-is-here/59 |url-status=live |archive-url=https://web.archive.org/web/20100513014916/http://www.zdnet.com/blog/ou/high-definition-video-conferencing-is-here/59 |archive-date=2010-05-13 |website=[[ZDNet]]}}</ref><ref>[http://www.jkcit.co.uk/news/20060522.htm Polycom High-Definition (HD) Video Conferencing] {{webarchive|url=https://web.archive.org/web/20160416002711/http://www.jkcit.co.uk/news/20060522.htm|date=2016-04-16}}</ref> [[:en:Polycom|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 [[:en:Mobile_device|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. [[:en:Mobile_collaboration|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.<ref>[http://communication.aver.com/model/VCLink VCLink for Mobile Devices—AVer Video Conferencing] {{webarchive|url=https://web.archive.org/web/20170313105857/http://communication.aver.com/model/VCLink|date=2017-03-13}}</ref>
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 [[:en:Smartphone|smartphone]] with a [[:en:Broadband_Global_Area_Network|BGAN satellite modem]] to make a videocall to the [[:en:BBC|BBC]] from the summit of [[:en:Mount_Everest|Mount Everest]], at {{convert|8,848|m}} above sea level.<ref>Callaham, John. [http://www.neowin.net/news/man-makes-the-highest-skype-video-call-ever-on-top-of-mount-everest Man makes the highest Skype video call ever on top of Mount Everest] {{webarchive|url=https://web.archive.org/web/20170519041243/https://www.neowin.net/news/man-makes-the-highest-skype-video-call-ever-on-top-of-mount-everest|date=2017-05-19}}, Neowin.net website, June 25, 2013; which in turn cites:
* Larson, Stephanie. [http://blogs.skype.com/2013/06/24/first-skype-call-atop-mt-everest-raises-thousands-for-charity/?cm_mmc=SMTW%7C7001_B1-_-Outgoing%20-%20User%20Stories First Skype Call Atop Mt. Everest Raises Thousands for Charity] {{webarchive|url=https://web.archive.org/web/20160328072753/http://blogs.skype.com/2013/06/24/first-skype-call-atop-mt-everest-raises-thousands-for-charity/?cm_mmc=SMTW%7C7001_B1-_-Outgoing%20-%20User%20Stories|date=2016-03-28}}, [[Skype|Skype blog]], June 24, 2013.</ref>
The [[:en:COVID-19_pandemic|COVID-19 pandemic]] resulted in a significant increase in the use of videoconferencing. Berstein Research found that [[:en:Zoom_(software)|Zoom]] added more subscribers during the first two months of 2020 alone than in the entire year 2019. [[:en:GoToMeeting|GoToMeeting]] had a 20 percent increase in usage, according to [[:en:LogMeIn|LogMeIn]].<ref>{{cite news |last=Beauford |first=Moshe |date=March 5, 2020 |title=With COVID-19 Spreading, Video Conferencing is Booming |work=[[UC Today]] |url=https://www.uctoday.com/collaboration/video-conferencing/with-covid-19-spreading-video-conferencing-is-booming/ |access-date=May 21, 2020}}</ref> UK based [[:en:StarLeaf|StarLeaf]] reported a 600 percent increase in national call volumes.<ref>{{Cite web |date=2020-05-01 |title=StarLeaf {{!}} StarLeaf Reveals Scale of Uptake in Video Conferencing Services During Coronavirus Pandemic |url=https://www.realwire.com/releases/StarLeaf-Reveals-Scale-of-Uptake-in-Video-Conferencing-Services |access-date=2020-07-24 |website=RealWire}}</ref> Videoconferencing became so widespread during the pandemic that the term [[:en:Zoom_fatigue|Zoom fatigue]] came to prominence, referring to the taxing nature of spending long periods of time on videocalls.<ref>{{cite news |last1=Jiang |first1=Manyu |date=22 April 2020 |title=The reason Zoom calls drain your energy |agency=[[BBC]] |url=https://www.bbc.com/worklife/article/20200421-why-zoom-video-chats-are-so-exhausting |access-date=30 October 2020}}</ref>
On 21 September 2021, [[:en:Facebook|Facebook]] launched two new versions of its Portal video-calling devices, the Portal Go and Portal Plus. The new video calling devices include the first portable variety of the hardware and number of updates.<ref>{{cite web |date=21 September 2021 |title=Facebook announces new Portal video-calling devices, Portal for Business service |url=https://www.cnbc.com/2021/09/21/facebook-announces-portable-portal-go-portal-for-business.html |accessdate=21 September 2021 |website=CNBC}}</ref>
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