Videophone: Difference between revisions
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==Early history== |
==Early history== |
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The first public video telephone service was opened by the [[German]] [[Reichspost]] in 1938 and closed due to the war in 1940. Video telephone lines linked Berlin to Nuremberg, Munich, and Hamburg. The terminals were integrated in public telephone booths and transmitted at the same resolution as the first German TV sets, at 440 lines. The British [[General Post Office]] operated another public video telephone service prior to World War II. |
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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 [[Cathode Ray Tube|CRT]] display in the cabinet. The camera was located atop the screen, to help users see eye to eye. |
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 [[Cathode Ray Tube|CRT]] display in the cabinet. The camera was located atop the screen, to help users see eye to eye. |
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Revision as of 16:32, 5 February 2009
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
The first public video telephone service was opened by the German Reichspost in 1938 and closed due to the war in 1940. Video telephone lines linked Berlin to Nuremberg, Munich, and Hamburg. The terminals were integrated in public telephone booths and transmitted at the same resolution as the first German TV sets, at 440 lines. The British General Post Office operated another public video telephone service prior to World War II.
Two decades later, in 1955, Gregorio Y. Zara, a Filipino engineer and a graduate from the Massachusetts Institute of Technology, invented another 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. The camera was located atop the screen, to help users see eye to eye.
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. It was limited by connecting by analog phone lines at about 19 kbit/s; the video portion was 11,200 bit/s, 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. Henderson[1]. 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 public acceptance
Early AT&T Picturephones had few users, in part because the service was expensive. It cost approximately USD$90 per month in 1974. However as modern technology reduced the costs to nominal (see: webcams and UMTS), videophones continue to be marginaly used. This contrasts to the unanimous certainty of pundits through many decades that videophones would be an obvious, highly sought-after technology. One reason may be that even today videophones are a poor analog for face-to-face conversation. Primarily, users mutually look at the video screens and not at the video cameras, causing the eyes to take on an unnatural downward glance, as the camera is usually just above the screen on almost all videocall enabled cellphones. Some argue that this effect is easily negated by holding the cellphone slightly away when videocalling. Another reason may be that people actually desire less fidelity in their communication, as evidenced by the popularity of written conversation (ie texting and instant messaging, which is available on all video-enabled cell phones and webchat programs).
Although it could also be still argued that for users who would benefit most from videophone services (e.g. members of a family living on different continents, i.e. who may have a strong desire, but little opportunity for face-to-face conversations), costs are still largely prohibitive: inexpensive international solutions for video data transfer (such as 3's Skype enabled cell phones) only cover a handful of countries at the moment.
Special high value verticals are in play at the moment as data speeds and hardware is catching up to the requirements and demands of videocalling. Healthcare, education, construction, government, and other enterprise level applications are driving the growth of video conferencing.
Most frequent usage of videocalling over HSDPA 3.5G networks in Europe as of 2008 appears to be aimed at locale transmission, i.e. live video of where one is as opposed to self image. The preferred method is stated by some to be using the larger megapixel camera on the back of the phone rather than the smaller camera infront. In this way the sender maintains an overview of the live video transmission on the screen as it is being sent.
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.
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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 interpreter 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.
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. This proves users are eager to use videophones, but are likely to trade convenience for cheaper costs. As long as cheaper alternatives are available, unless a dedicated services provides tremendous added value at a reasonable cost, it's unlikely the dedicated solution will spread much.
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.
In popular culture
- In many science fiction movies and shows that take place in the future, videophones are used as a primary method of communication. One of the first movies where a video phone was used is Fritz Lang’s Metropolis.
Examples of videophones include the Picturephone from Pee-wee's Playhouse, 2001: A Space Odyssey, Space: 1999 and Blade Runner, and on the British cartoon DangerMouse, in which the title character regularly communicated with headquarters via videophones in both his home and his car. Another similar device was featured in the 1944 Warner Bros. cartoon, Plane Daffy, which the female spy Hatta Mari used to communicate with Adolf Hitler. Of particular note, the videophone was a staple, everyday technology in the futuristic Hanna Barbera cartoon The Jetsons. - A device with the same functionality has been used by comic strip character Dick Tracy since 1964. Called the "2-Way Wrist TV", the fictional detective often uses the phone to communicate with police headquarters.
- AT&T VideoPhone 2500 prototypes are visible in the movie Gremlins 2: The New Batch.
- In Futurama, the videophone is often used in the delivery service spaceship.
See also
