Idea: The ultimate CD/DVD auditing tool
zenadsl6186 at zen.co.uk
Tue Jul 8 18:47:40 PDT 2003
the nyquist/lindquist/someone-else-who-was-pissed sampling theorems are
based on the possibility of mathematically extracting frequencies from
digital information in a STEADY_STATE situation.
That doesn't mean that a speaker will properly reproduce those frequencies.
Consider the dynamics of energy transfer. A digital signal at
near-1/2-sampling frequency will have two datum points. The transitiion
between them will be dramatic! the possibilities of energy transfer will not
be comparable to an analogue sinusoidal waveform.
and i missed a bit or two. Consider the entropic uncertainty of a signal
that has two-and-a-bit datums, against a sine wave. Start from zero, and go
to such a waveform. Is it a constant-amplitude sine wave at frequency z? or
a decaying sine at a frequency (z-at)?
There's more, and it's to do with the limits of fourier and sampling theory.
Say you have a wave at a frequency of z that's sampled according to nyquist
theory. can you distinguish it from a wave of a frequency z - delta z? It
can be done, but it takes a while, and a good few samples to do it. And a
good analogue system will do it quicker.
someone (hopefully not me, i haven't the time just now) can probably apply
wavelet theory and get all this from steady-state theory, and tie it up in a
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