Print

Print


----- Original Message -----
From: "Don Cox" <[log in to unmask]>
> On 22/04/04, Steven C. Barr wrote:
>
> > Don't the bits on a CD actually represent some sort of pulse-code
> > description
> > of the digital waveform, as opposed to the actual waveform making up
> > the music?
>
> There is no such thing as the "digital waveform".
>
> Each 16-bit number in the sequence represents the voltage that should be
> present at the output of the CD player at that moment. The next number
> represents the voltage 1/44100 second later. (And there are two channels
> of course).
>
> It is quite simple. The D to A converter accepts a 16-bit number on its
> logic inputs and outputs a voltage. Difficult to engineer accurately,
> but the principles are straightforward.
>
> See Watkinson, "Art of Digital Audio" for details.
>
>
> >  If so, are .WAV files stored in such a way they use the
> > same algorithms
> > rather than being a representation of the signal values themselves?
>
> The numbers in an ordinary 16-bit 44.1KHz WAV file are exactly the same
> as those on an audio CD. The difference is that a WAV file might have a
> different number of bits, or sampling frequency, so it needs a header to
> say what these are, and how many channels are present.
>
> Most WAV and AIFF files are 2-channel 16-bit 44.1KHz, in my experience.
Then is it the bits (pits and lands) on the CD surface that represent the
ones and zeros after being processed by an algorithm so that sequences of
either can be compressed? Thus, reprocessing the ones and zeroes with the
same algorithm creates the .wav file?
(decimal:)                           (0)       (63)     (255)    (252)
Thus, if the waveform in digital is 00000000 00111111 11111111 11111100...
the actual bits on the CD surface represent the lengths of those strings
of ones and strings of zeroes rather than the bits that compose the
digitized
waveform themselves...right?
Steven C. Barr