 Digital television is based on the idea of recording information in a digital, rather than an
analogue format. The idea is to reduce the information to a series of electronic signals, which can be written in a code of 0's and 1's. This
binary codeis the way computers 'talk' to each other. It is preferable to
magnetic tape, the analogue method of storing information, as there is less likelihood of corrupting the signal and the information is stored on formats like
Compact Discswhich are more durable than the traditional magnetic tape.
The idea of digital recording has been around for a long time. The IBA ( the forerunner of the Independent Television Commision) licenced the first digital tape recorder in the early 1980's. However the first advance in recording was an
improvedanalogue system, BetaCam. This was a component analogue system where the information was split up into colour and
luminance, stored on separate tracks. This gave a higher picture quality, but was overtaken in the early 1990's by digital systems, such as DigiBetaCam. These give an even better picture and make editing with on-line computer systems possible.
In the television industry the use of DVC and DVD (Digital Video Cassette and Digital Video Disk) are widespread. This means that recording has recently been standardized again. The broadcast industry standard is now MPEG-2 (Motion Picture Experts Group standard 2). This cuts the amount of information from nearly 100 million 'bits' per second to less then 5 million. It does this by not specifying the information for each individual
pixel, but rather the boundaries of groups of pixels of the same colour and brightness.
Although the use of digital technology in recording television is now quite established, the next step is to broadcast the information digitally. This is the 'revolution' which is currently being discussed
at length.
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note:
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analogue format: 模拟形式
binary code: 二进制码
magnetic tape: 磁带
compact discs: 光盘
improved: 改良的
luminance: 亮度
pixel: 像素
at length: 详细的
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