AskDefine | Define videophone

User Contributed Dictionary

English

Noun

  1. a telephone capable of transmitting both audio and video signals in both directions

Extensive Definition

A videophone, also known by the trademarked name Picturephone, is a telephone which is capable of both audio and video duplex transmission. It differs from videoconferencing in that it expects to serve individuals, not groups.

Early history

In 1955, Gregorio Y. Zara, a Filipino engineer and a graduate from the Massachusetts Institute of Technology, invented the first videophone, known as the "photo phone signal separator network."
Meanwhile, AT&T conducted experiments and demonstrations of a Picturephone product and service in the early 1960s, including at the 1964 New York World's Fair. The demo unit was usually in a small oval cabinet on a swivel stand, intended to stand on a desk. Videophones, possibly AT&T 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. Color was not employed. The equipment packaged a Plumbicon camera and a small CRT display in the cabinet. Video bandwidth was 1 MHz with vertical scan rate of 30 Hz, horizontal scan rate of 8 KHz, and about 250 visible scan lines. The equipment included a Speakerphone hands free telephone, with an added box to control picture transmission. Each Picturephone line used three twisted pairs of ordinary telephone cable, two pairs for video and one for audio and signaling. Cable amplifiers were spaced about a mile apart (1.6 Kilometers) with built-in six-band adjustable equalization filters. For distances of more than a few miles, the signal was digitized at 2 MHz and 3 bits per sample DPCM, and transmitted on a T-2 carrier.
The Picturephone was offered to the public in New York City, Washington, DC, Chicago, and Pittsburgh in 1970. The screen was larger than in the original demo units, approximately half a foot (15 cm) square in a roughly cubical cabinet. Picturephone booths were set up in Grand Central Station and elsewhere. With fanfare, Picturephones were installed in offices of Westinghouse in Pittsburgh, and at 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 into 5XB switch offices, this being the most widespread of the relatively modern kinds. Unrelated difficulties at New York Telephone, however, slowed the effort there, and few customers signed up in either city. A 6 September 2001 report on CNN said the Picturephone service only had a total of 500 subscribers at its peak, and the service faded away by 1974.
AT&T sold the VideoPhone 2500 to the general public in 1992 to 1995 with prices starting at US$1,500 and later US$1,000.http://www.bellsystemmemorial.com/telephones-picturephone.html It was limited by connecting by analog phone lines at about 19 kbit/s; the video portion was 11,200 bit/s,http://discover.com/issues/oct-92/features/1992discoverawar131/ with a maximum frame rate of 10 frames per second, but typically much lower. The VideoPhone 2500 used proprietary protocols.
In 2007, the Smithsonian's National Museum of American History received a wireless picturephone prototype known as intellect, developed in 1993 by inventor Daniel A. Hendersonhttp://americanhistory.si.edu/news/pressrelease.cfm?key=29&newskey=611. This system and device was designed to receive pictures and video data from a message originator to a message center for transmission and display on a wireless portable device such as a cellular telephone. See also camera phone.

Lack of early public acceptance

Early AT&T Picturephones did not meet with widespread adaptation in the public marketplace, in part because for new innovative technologies to be accepted, '...they must deliver.... enough benefits to make (the) change worthwhile' . Promoters believed that if hearing someone over the phone was pleasing, then seeing them at the same time would be that much better. However the hefty cost to use an AT&T Picturephone, at approximately $US90 per month in 1974, greatly outweighed its benefit. The Picturephone's advantage "was superfluous, adding little information to voice alone, especially considering its high price" said Kenneth Lipartito, a professor of history at Florida International University.

Protocols

The original Picturephone system used contemporary crossbar and multi-frequency operation. Lines and trunks were six wire, one pair each way for video and one pair two way for audio. MF address signaling on the audio pair was supplemented by a Video Supervisory Signal (VSS) looping around on the video quad to ensure continuity. More complex protocols were later adopted for conferencing.

Call setup

Videoconferencing in the late 20th century was limited to the H.323 protocol (notably Cisco's SCCP implementation was an exception), but newer videophones often use SIP, which is often easier to set up in home networking environments. H.323 is still used, but more commonly for business videoconferencing, while SIP is more commonly used in personal consumer videophones. A number of call-setup methods based on instant messaging protocols such as Skype also now provide video. The principal open systems SIP source is Counterpath Corp., which provides support for British Telecom, Deutsche Telekom, Sprint, Telmex, AT&T's Callvantage, and the unified communicator of Cisco and Verizon.
Another protocol used by videophones is H.324, which mixes call setup and video compression. Videophones that work on regular phone lines typically use H.324, but the bandwidth is limited by the modem to around 33 kbit/s, 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

The most commonly used video codecs are H.263 and H.264. Skype uses the proprietary protocol VP7. VZOchat uses proprietary Visicron codec.

Videophone streaming

Qik is a little piece of software that enables you to stream videos directly from your phone to the Web. . Livecastr performes a similar function. Compared to Qik Livecastr uses a standard protocol for mobile video calling instead of a broadband wireless connection. This results in a slightly lower video quality. Livecastr can be used with any 3G mobile phone and does not require installation of an application on the handset.

Current use

The widest deployment of video telephony occurs in mobile phones, as nearly all mobile phones supporting UMTS networks work as videophones using an internal camera, and are able to make video calls wirelessly to other UMTS users in the same country or internationally. As of Q2 2007, there are over 131 million UMTS users (and hence potential videophone users), on 134 networks in 59 countries.
Videophones can be used by the deaf to communicate with sign language over a distance. In the US the FCC pays companies for providing Video Relay Service to deaf and hard-of-hearing individuals, where they use a videophone to talk through a sign-language translator to people using audio phones. Videophones are also used to do on-site sign-language translation (Video Remote Interpreting). The relatively low cost and widespread availability of mobile phones with video calling capabilities have given deaf people new possibilities to communicate with the same ease as others, with some wireless operators even starting up free sign language gateways.
Videotelephony is used in large corporate conferencing setups, and is supported by systems such as Cisco Unified Communications Manager, and similar systems from companies such as Tandberg, Radvision, and Polycom.
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 and free instant messenger programs. Thus an activity that was disappointing as a separate service found a niche as a minor feature of products intended for other purposes. 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

Softclient videophones

videophone in German: Bildtelefon
videophone in French: Visiophonie
videophone in Indonesian: Videophone
videophone in Italian: Videochiamata
videophone in Malay (macrolanguage): Telefon video
videophone in Dutch: Beeldtelefoon
videophone in Japanese: テレビ電話
videophone in Polish: Wideofon
videophone in Swedish: Bildtelefon
videophone in Chinese: 視訊電話
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