Wait, so aliasing occurs when the signal is sampled? So if i have this patch :
[adc~] | | | [dac~] and if the signal already contains frequencies above the Nyquist, i will get aliasing? I generally use my electric guitar as the main audio source, and i'm assuming that it has lots of harmonics beyond the Nyquist frequency (especially when the strings are new), yet i never noticed any distortion of any sort. I might have a bad ear... Or is it just that the energy of the upper harmonics is too low for me to notice when they cause aliasing? Pierre 2010/4/1 Matteo Sisti Sette <matteosistise...@gmail.com> > > Correct, nothing played back at original sampling rate will alias. > > It _won't_ alias; it may already _have_ aliased when sampled in the first > place. > > Aliasing occurs when sampling. > > When you digitalize (ADC), you are sampling. When generating a waveform > mathematically, you are sampling the mathematical function at the very > moment you compute its value at discrete points. > > When you play back a signal at a different speed than the original, you are > _resampling_ it, that is, theorically, interpolating it and then sampling it > again, and it is the sampling stage, not the interpolating one, that > produces the aliasing. > > The interpolation, since it cannot be an ideal interpolation, may introduce > other noises or artifacts, not aliasing as far as I can see. > > > -- > Matteo Sisti Sette > matteosistise...@gmail.com > http://www.matteosistisette.com >
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