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通信工程专业英语TEXT1信息的数字表示

发布时间:2014-01-12 10:01:51  

any medium, be it a text, an image, or a sound, is coded in a unique form which ultimately results in a sequence of bits, all kinds of information can be handled in the same way and by the same type of equipment.

Furthermore, transformations of digital information are while analog transformations introduce distortions and noise.

1 Storage

The same digital data storage device can be used for all media. The only difference may lie in size requirement.

Still images and motion video require larger volumes than text or graphics. Sound also is demanding though less so than imaging. Thus, appropriate digital devices may be required, But the key point is that a single type of digital device may store all kinds of information.

2. Transmission

Any data communication system capable of carrying bits has the potential to transmit any multimedia digital information. Thus, a single communication network supporting digital

(ISDN), which is a facility aimed at integrating the transport of all information media.

The difficulties may Even when the potential for integrating different types of information on a single communication system is not exploited, the benefits of digital versus analog transmission are Fourth,

3. Processing

As all information is stored on computers, it can be processes, analyzed, modified, altered, or complemented by computer programs like any other data. This is probably where the potential is the highest.

? and An example of advanced contents recognition is the detection of cuts in motion video to automatically identify and index video sequences. ? Data structures, chaining using pointers between information elements, may be

created for faster and flexible retrieval(检索).

? Powerful editing by cut-and-paste functions to create monomedia (e.g. sound only) or

multimedia documents is possible.

? The quality of information may be improved by the removal(移除)

? Information of a similar type but created through different processes---such as motion

imaging synthesized by computers and camera-captured video--- may be mixed.

? To summarize:

? Digital representation permits the storage of different information types on the

same device. Information may also be transmitted over a single digital network. Likewise, when digitized, all forms of information may be treated by computer programs, for editing, quality improvement, or recognition of the meaning of the information.

4. Drawback (缺点,不足)of Digital Representation of Continuous Information

The major drawback of the digital representation of information lies in coding distortion. The process of first sampling and then quantizing and coding the sampled values introduces distortions. As a result, the signal generated after digital-to-analog conversion and presented to the end-user has little chance of being completely identical to the original signal.

Increasing the sampling rate and multiplying the number of bits used to code samples reduces the distortion. The result is an increased number of bits per time or space unit, called bit rate, storage capacity is not infinite, and transmission systems also have limited bandwidths.

One of the key issues then is to choose an appropriate balance between the accuracy of the digitization, which determines the bit rate, and the perceived(感知,觉察)distortions by users. are physically.

Another consequence, as mentioned before, is the need for a large digital storage capacity (装满)the 80 megabyte hard disk of a standard personal computer.

Fortunately, compression algorithms have been developed to alleviate(缓和,减轻)these requirements. But only spectacular recent progress in digital storage capacity and cost has enabled the development of massive digital storage of media such as images, sound, and motion video.

Let us summarize:

The digitization process introduces a distortion of the information. Reducing this distortion may be achieved by increasing the sampling rate and the number of bits to code each sample. Images, sound, and motion video require a large amount of digital storage capacity.

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