[PD] better tabread4~
Mathieu Bouchard
matju at artengine.ca
Fri Jun 20 20:15:41 CEST 2008
On Wed, 11 Jun 2008, cyrille henry wrote:
> ok, if you don't wish to compile in order to test, here are 2 samples :
> http://www.chdh.free.fr/tab/tabosc4.wav
> http://www.chdh.free.fr/tab/tabosc4c.wav
> note that this is the worst case for tabread4~ : a very small table play at low frequency.
I believe that the difference will be more perceivable in non-sound
contexts or at least non-waveform contexts, e.g. video/OpenGL, or
sequencing.
> for bigger table, the difference can be very small.
For a normal 4-point interpolator, the size of the table does not matter,
because you always only use the previous two points and the next two
points. It's just the scale at which you are looking at the thing, that
gives the impression of large details.
I tried [tabread4] between two arrays of different sizes, to visualise
interpolation, and just clicking around in one array for a few minutes got
me to produce quite wild discontinuities of first derivative. This has
little to do with the twice-continuously-differentiable (C2) nice things
that I learned in school and such.
In very large tables, the interpolation will get lousy because the
resolution of floats gets too close to the resolution of the table indices
themselves (that is, there are not enough fractions between two
consecutive integers). But this does not happen at the beginning of the
table. On average, though, or on worst-case (which often matters), bigger
tables make things worse in pd.
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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal, Québec
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