Alright, i got it! Thanks everybody!
Pierre
Pierre Massat a écrit :yes
Wait, so aliasing occurs when the signal is sampled?
yes, it will.
So if i have this patch :
[adc~]
|
|
|
[dac~]
and if the signal already contains frequencies above the Nyquist, i will get aliasing?
so usually, your sound card have an analog filter prior to digital convertion in order to reduce aliasing.
cyrille
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?2010/4/1 Matteo Sisti Sette <matteosistisette@gmail.com <mailto:matteosistisette@gmail.com>>
Pierre
matteosistisette@gmail.com <mailto:matteosistisette@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
http://www.matteosistisette.com
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