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.

Don Cox
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