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19. Content > Audio

Audio

Most audio formats encode point-by-point air pressure over time using 8-bit samples, giving 256 possible amplitudes. This technique is known Pulse Code Modulation (PCM). Some formats distribute audio linearly, while others take advantage of the fact that humans hear in a nonlinear way. That is, humans have a harder time distinguishing two loud sounds than two soft sounds, so encodings are assigned more densely at small amplitudes.

All of the following formats use PCM in one way or another:

  • Sun’s .au

  • Microsoft’s .wav

  • Apple’s AIFF

  • mu-law (U.S. telephony)

  • A-law (European telephony)


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