QQ asked in 社會與文化語言 · 1 decade ago


Analog to Digital Conversion: Pulse Code Modulation

Pulse code modulation, or PCM, is the standard choice for representing analog signals in the modern telephone system. It is also the basis for almost all computer sound reproduction. Compact discs also use PCM to represent sound. To understand how it works, you need to understand two concepts, sampling and quantization. Sampling is the periodic measurement of a continuous or analog signal. The idea behind sampling is to represent an information signal in abbreviated form by taking periodic snapshots of the waveform’s voltage. A motion picture works the same way as a sampled waveform—it consists of a set of picture frames (analogous to the waveform samples). Because the film’s frames are shown in rapid sequence, they appear to recreate the continuous motion of the subject. Figure 14—17 illustrates this concept.


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  • 1 decade ago
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    類比到數字的變換︰ 脈碼調製

    脈碼調製或者PCM,是在現代電話系統裡代表類比信號的標準選擇。 這也是幾乎所有計算機聲音再生的基礎。 光碟也使用PCM 描述聲音。 為了理解它怎樣工作,你需要理解兩個概念,取樣和quantization。 取樣是一個連續或者類比信號的定期測量。 取樣的後面的那些想法描述訊息信號在被花費定期對那些波形電壓的快照縮寫形式。 一部電影工作與一取樣的waveformt相同的模式由一套圖象幀(對波形樣品類似)組成 . 因為電影框架被按照迅速的順序放映,他們看起來再創造主題的連續的運動。 圖14 7 說明這個概念。

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  • 1 decade ago


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