[music-dsp] Resampling, Interpolation

andy butler akbutler at tiscali.co.uk
Sun Oct 7 07:36:52 EDT 2007

Here's a little demo I made.


Started with a 1kHz sine tone (made in audition)
of 2s duration (repeated 2x)
...at 44100Hz sample rate

Resampled the first repeat using linear interpolation,
so that pitch drops linearly down to zero over the 2s

There's audible artifacts.
I'd call it aliasing, but not sure if it 100% matches the technical description.

If, as seems to be stated on this list, linear interpolation is good for 
8x oversampled signals then the 1000Hz tone sampled at 44100Hz wouldn't
give aliasing when re-sampled.
Surely,  this demonstrates something interesting.

Either that, or I misunderstood what was being said ;-) 

To prove that the artefacts are the linear interpolation,
and not some quirk of my programming the second repeat
is shifted using identical software 
apart from the interpolation (Mathons Chopitch).

andy butler

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