Pierre Massat a écrit :
Wait, so aliasing occurs when the signal is sampled?
yes
So if i have this patch :
[adc~]
|
|
|
[dac~]
and if the signal already contains frequencies above the Nyquist, i will
get aliasing?
yes, it will.
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?
Pierre
2010/4/1 Matteo Sisti Sette <[email protected]
<mailto:[email protected]>>
> 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
[email protected] <mailto:[email protected]>
http://www.matteosistisette.com
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