On Wed, 31 Oct 2001, Robert Benschop wrote:
> on 31-10-2001 8:35, Michael J. Hu=DFmann at michael_at_michael-hussmann.de wrote=
> :
>
> > Indeed. If audio CDs used compression, this would have to be the only
> > kind of compression that saves no space whatsoever -- a 1:1 compression
> > ratio. No wonder this was kept a secret ... ;-)
>
> I'm not a audio technician (far from it, as you can tell ;-) but just to
> give it a shot, what about 44.1 KHz, isn't that what CD are encoded at ?
Ohhh, I've heard these arguments before in an ancient thread I believe.
It's all in how you define what "compression" really is. The
Merriam-Webster Online Dictionary says:
http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=compress
"to reduce in size or volume as if by squeezing"
...which doesn't really help.
In short, any digital representation of anything natural (analog) is going
to be a compression. When you experience a live performance, you are
hearing the results of a theoretically infinite number of interactions:
the music reaching your ears comes directly from the instruments, but is
modified by the sound reflecting off of walls, the earth, other people,
each blade of grass, etc etc.
To record this performance for posterity, we can't possibly record
everything - that would take an infinite amount of space. Microphones do
a good job, but they are still limited - they can't measure everything.
So even an analogue recording of music is "compression", if you want to
define it so loosely - but most people would rather say that it is an
/encoding/ of the original performance. Digital recording techniques use
the same analogue methods (the microphone, guitar pickup, whatever) and
take samples of it very very fast. By taking many instantaneous
measurments of the analogue, the digital begins to sound (to our ear) very
much like the analogue recording.
(A similar example is how a film projector works: each second of film is
actually 24 still frames - 24 instantaneous samples of that original
analogue second. The film projector shows us the stills very quickly, at
the original rate of course (24fps) and to the eye it looks as if movement
is occuring)
Gee, I hope that clarified things...
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