 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
code is 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 Discs which 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
improved analogue 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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