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Early History AT&T conducted experiments and demonstrations of a Picturephone product and service in the early 1960s. Videophones, possibly ATT units , were featured at the Telephone Association of Canada Pavilion (The 'Bell' Pavilion) at Expo 67, an International World's Fair held in Montreal, Canada in 1967. Several demonstration videophone units were available for the Fair-going public to try, who were permitted to make live video calls to recipient volunteers in the United States. Picturephone was offered to the public in New York City and Washington DC in the early 1970s. Picturephone booths were set up in Grand Central Station and elsewhere. With fanfare, Picturephones were installed in offices of Westinghouse and other progressive companies. Hundreds of technicians attended schools to learn to operate the Cable Equalizer Test Set and other equipment, and to install Picturephones. New wideband crossbar switches were designed and installed. Unrelated difficulties at New York Telephone, however, slowed the effort there, and few customers signed up in either city, and the service faded away after a few years. AT&T sold the VideoPhone 2500 to the general public in 1992 to 1995 with prices starting at US$1500 and later US$1000.* It was limited by connecting by analog phone lines at about 19Kbps; the video portion was 11,200bps,* with a maximum frame rate of 10 frames per second, but typically much lower. The VideoPhone 2500 used proprietary protocols. Call Setup Videoconferencing previously was limited to the H.323 protocol (notably Cisco's SCCP implementation was an exception), however recently a shift towards SIP videophones has occurred. In accordance with the adoption of SIP telephony for home users, videotelephony is also slowly becoming available to home users from a number of hardware and software providers. Closed solutions such as Skype also now provide video. Another protocol used by videophones is H.324. Videophones that work on regular phone lines typically use H.324, but the bandwidth is limited by the modem to around 33Kbps, limiting the video quality and framerate. A slightly modified version of H.324 called 3G-324M defined by 3GPP is also used by some cellphones that allow video calls, typically for use only in UMTS networks. Video Compression Main article: Video compression The most commonly used video codecs are H.263 and H.264. Skype uses the proprietary protocol VP7. Current use Videotelephony is mostly used in large corporate conferencing setups, and is supported by systems such as Cisco CallManager. Other companies such as Tandberg, Radvision, and Polycom also offer similar solutions. Today the principles, if not the precise mechanisms of a videophone are employed by many users world-wide in the form of webcam conferences using personal computers with cheaply available webcams and microphones. A videophone can be created by using an old or inexpensive computer and dedicating it to run a video softphone. In 2004 Telmex, the biggest telephone service provider in Mexico, introduced Videophone service over regular phone lines (apparently H.324). The service, as of March 2006, had not enjoyed widespread adoption. Telecom Italia supplies LG-Nortel videophones, which also appear to be used by Telmex. Trivia See also Dedicated videophones Softclient videophones | |||||||||
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