[music-dsp] Waveform Interpolation

Peter Schoffhauzer scoofy at inf.elte.hu
Thu Dec 9 06:05:50 EST 2010


andy butler wrote:
> what's not clear to me is how a "low pass filter"
> could produce harmonically unrelated artefacts.
> 
> Are you saying that linear interpolation is artefact free?

I'd say it's not the interpolation/filtering is what creates the 
artifacts. The aliasing is created by the resampling, and the 
interpolation is just filtering/reducing those artifacts caused by the 
resampling. If you compare the frequency spectrum of zero order hold, 
linear interpolation and higher order polynomial interpolators, you'll 
see that all these look like zero order resampling, except that the 
interpolators smooth/filter/attenuate the alias images. So the 
interpolation (either linear or other) doesn't create/add new artifacts, 
just filters/attenuates the aliasing.

Peter



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