[PD-dev] query: upsampled block~ objects and inlet~

Tim Blechmann TimBlechmann at gmx.net
Sun Jul 17 11:33:41 CEST 2005


hi miller, 

> I just started playing with up-sampled sub-patches (thanks Iohannes),
> and found out that the inlet~ object upsamples its input by
> interspersing zeros with the samples coming in.  So for instance, if
> you're upsampling by four and put in 1, 1, 1, ... you get out 1, 0, 0,
> 0, 1, 0, 0, 0, 1, ...
well, i think, upsampling is used especially for ffts ... there
zero-padding is usually the wanted behaviour...

> It seems to me the best default behavior would be to have a, b, c, ...
> turn into a, a, a, a, b, b, b, b, c, c, c, c, ... so that you would
> get at least "reasonable" behavior (and anyway, it's no more expensive
> than the current setup.)  Would this break people's patches that use
possibly ... without doing the math, one will probably add information
to an fft so this will change the precision of the fft ... on the other
hand, this effect is minimal (see attached patch) and could be resolved
by having an inlet~ option "zero-pad" 

> upsampling?  I assume people use some kind of filter after the inlet~
> object, and am hoping that, whatever the most popular filters are,
> they only look at every nth (4th, for instance) sample of the input,
> so nothing should be broken by doing this...
well, i guess, they don't use filters, but the sample&hold / linear
interpolation ;-)

cheers ... tim

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