[PD] tabread4~ "broken" interpolation algorithm - was Re:, Max Smoother Audio than Pd?

Matteo Sisti Sette matteosistisette at gmail.com
Tue Mar 30 15:52:04 CEST 2010


Matt Barber escribió:
> Yes, as far as I know it's identical -- when you do one of these
> interpolations with four points, you can either think of it in terms
> of a cubic polynomial formula involving those four points, or in terms
> of the sum of four scaled "basis functions" - the latter seems to me
> intuitively equivalent to direct convolution of an impulse response
> centered on the four points, and scaled to each.  It will be limited
> by the quantization of the index, so in that sense it might not be
> linear..

Hmm, by linear I mean that the interpolated version of the sum of any 
two discrete signals is equal to the sum of the interpotated versions of 
each one. It shouldn't be difficult to tell whether this is true or not 
by looking at the formulas but I'm too lazy right now :P

If the transformation is not linear, then there is no "impulse response" 
at all nor any "frequency response" strictly speaking, thought that 
doesn't mean that it doesn't make sense to do some reasoning in terms of 
impulse or frequency response under certain simplifications or 
assumptions - i.e. to speak less strictly....



-- 
Matteo Sisti Sette
matteosistisette at gmail.com
http://www.matteosistisette.com




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