Digital vs. Analog

[P3D Jim Roberts <xjim@xxxxxxxxxxxxxxxx>]

None of this is news to a large part of this list, so feel free to ignore this.

I feel obligated to step into this slightly off topic discussion, since
one of the few things I have actually been trained for is digital signal
processing (both sound and image.)

The main thing to keep in mind is the resolution capability of the receiving
system.  As a general rule, for example, people can not hear the difference
between an analog sound and its sampled sound (sampled at 44.1 kHz) if the D/A
converter is good (i.e. accurate with smoothing filters, though the smoothing
filters should not actually be necessary, either, because the harmonics are
all beyond human hearing.)  Anyhow, there are no 'gaps' between the samples
in a reconstructed sound.  The difference in noticed in sound (the "warmth"
of vinyl, for example) is actually due to artifacts introduced along the path of
recording, manufacturing, and playback, and can be convincingly simulated with
DSP techniques.  CDs of albums previously released on vinyl sound different
("cleaner" or "harsher") because many of these steps are eliminated.

Regarding digital imaging, until image resolution can exceed that of the
human visual system (and I can't for the life of me remember how many cones
and rods we have, not to mention the interpolative capability of our
processing) there can be no comparison.  

Remember that 'analog' in most cases is not truly so - the resolution is
just beyond the resolution of the instruments being used to measure it.
Photographic
film has its upper resolution limit defined by the size and packing of the 
silver iodide crystals, for example, even though without magnification it may
appear to be continuous.

Hmmm - I don't appear to have had much point to this - I suppose I should
have a moral:  Digital systems are generally a poor substitute for analog
systems,
in absolute terms, but for many practical purposes can yield more reliable
performance.  I still haven't seen a digital imaging system that can compare
to even 35mm film, but I think CDs are incredibly better on most levels than
vinyl (and I use both.)

Boringly yours,

Jim



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