Text 2 Video telephony

Video telephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time.

At the dawn of the technology, video telephony also included image phones, which would exchange still images between units every few seconds over conventional POTS-type telephone lines, essentially the same as slow scan TV systems.

Currently video telephony usage has made significant inroads in government, healthcare, education and the news media. It is particularly useful to the deaf and speech-impaired who can use the technology with sign language and also with a video relay service, and well as to those with mobility issues or those who are located in distant places and are in need of tele medical or tele-educational services. It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships. Like all long distance communications technologies (such as phone and internet), by reducing the need to travel to bring people together the technology also contributes to reductions in carbon emissions, thereby helping to reduce global warming.

Video telephony developed in parallel with conventional voice telephone systems from the mid-to-late 20th century. Very expensive videoconferencing systems rapidly evolved throughout the 1980s and 1990s from proprietary equipment, software and network requirements to standards-based technologies that were readily available to the general public 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 video telephony become a practical technology for regular use.

With the rapid improvements and popularity of the Internet, video telephony has become widespread thru the deployment of video-enabled mobile phones, plus videoconferencing and computer webcams, which utilize 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.

The highest ever video call took place on May 19, 2013 when British adventurer Daniel Hughes used a smartphone with a BGAN satellite modem to make a video call to the BBC from the summit of Mount Everest, at 8,848 m above sea level.

Video telephony can be categorized by its functionality, that is to its intended purpose, and also by its method of transmissions.

Videophones were the earliest form of video telephony, dating back to initial tests in 1927 by AT&T. During the late 1930s, the post offices of several European governments established public videophone services for person-to-person communications utilizing dual cable circuit telephone transmission technology. In the present day standalone videophones and UMTS video-enabled mobile phones are usually used on a person-to-person basis.

Videoconferencing saw its earliest use with AT&T's Picture phone service in the early 1970s. Transmissions were analog over short distances, but converted to digital forms for longer calls, again using telephone transmission technology. Popular corporate videoconferencing systems in the present day have migrated almost exclusively to digital ISDN and IP transmission modes due to the need to convey the very large amounts of data generated by their cameras and microphones. These systems are often intended for use in conference mode that is by many people in several different locations, all of whom can be viewed by every participant at each location.

Telepresence systems are a newer, more advanced subset of videoconferencing systems, meant to allow higher degrees of video and audio fidelity. Such high-end systems are typically deployed in corporate settings.

Mobile collaboration systems are another recent development, combining the use of video, audio, and on-screen drawing capabilities using newest generation hand-held electronic devices broadcasting over secure networks, enabling multi-party conferencing in real-time, independent of location.

A more recent technology encompassing these functions is TV cams. TV cams enable people to make video “phone” calls using video calling services, like Skype on their TV, without using a PC connection. TV cams are specially designed video cameras that feed images in real time to another TV camera or other compatible computing devices like smartphones, tablets and computers.

Personal computer based web cameras are an often modest form of video telephony, usually used for point-to-point videophone calls.

Each of the systems has its own advantages and disadvantages, including video quality, capital cost, degrees of sophistication, transmission capacity requirements, and cost of use.

Unit 9 Radar

9.1 Read and translate the text. Use a dictionary to help you.

Date: 2016-03-03; view: 732