So we're back where I started to make comments on a while ago. Hmm, I
knew that.
Let's go over the problem shortly again, and let me give one pointer for
you guys (and gals ?) who feel lost about the perfection many of us
probably would like.
It isn't that we cannot create frequency limited signals, and please not
again some dumb-heinie-ness about given, long existing EE theory unless
you're a decent (and preferably, but not necessarily, mature)
mathematician about it, so for instance a wave table can be viewed as a
sum of sine waves, and for the sake of argument made to repeat ad
infinitum, so that essentially it's a bunch of sine waves. That can also
be thought to be true for a properly used iFFT, if the repeat factor is
exactly the length of the FFT interval (and no averaging with previous
FFT frames is considered).
The main problem is still that the waves that are generated by all kinds
of simulation software will in many cases still contain erroneous or
highly restrictive components, for instance with non-shift invariant
e-powers (which honestly can give horrendous signal distortion, I mean
certain methods of shifting samples can give dBs of different signal
amplitude, can't it ?), even if somehow you'd (additionally or
subtractively) frequency limit them, the resulting sample stream would
still sound a bit wrong on a standard DA converter, so maybe you'd want
to invert those high frequency patterns that form the error, and correct
for a specific kind of DACs, I don't know, but it's hard, that's for sure.
Theo V.
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