Alright, i got it! Thanks everybody! Pierre
2010/4/1 cyrille henry <[email protected]> > > > 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 >> >> >> >> ------------------------------------------------------------------------ >> >> >> _______________________________________________ >> [email protected] mailing list >> UNSUBSCRIBE and account-management -> >> http://lists.puredata.info/listinfo/pd-list >> >
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