[William Sommerwerck]

When you say digital, do you mean store the data as a number,
as is done now, and feed it to a DAC, the output of which is a
pulse width rather than a voltage? If so, that could be done with
the CDs we have right now.

Here we go...

When I say "digital", I mean "quantized" -- there is only a finite number of
possible pulse widths.

This is doable right now, and in fact was done 30 years ago, with the
original LaserDisks, which used a form of analog pulse-width modulation.