[gst-devel] GstController interpolation modes

[Sebastian Dröge]

On Mo, 2007-05-14 at 13:17 -0700, David Schleef wrote:
> > Additionally I would propose a trigonometric interpolation mode which
> > would interpolate the data points with a sum of sines. This would,
> > although being very computing intensive, offer the advantage that it
> > would give a periodic function. It would be sufficient to set a few data
> > points and have an always repeating sequence of parameter settings.
> 
> Summing trig functions doesn't have a whole lot of theoretical
> justification.  A sum of sinc() functions would give the effect you're
> looking for, and has a lot more research.  Even still, I think you're
> limited by the amount of information that the user is providing in
> the knots, rather than the theoretical model for interpolation.

Thanks for your answers.

Do you have URLs to some papers or articles about what you describe?
What I planned to do is explained on Wikipedia[0] and we also did this
in one lecture at university with the additional requirement of the data
points being equidistant (which we can't require for the controller
unfortunately) and then using the DFT to get coefficients for a real
trigonometric polynomial like[1].

Using sinc() sounds interesting too though, would be nice to have
something to read about interpolating with those :)

Bye

[0]http://en.wikipedia.org/wiki/Trigonometric_interpolation#Solution_of_the_problem
[1]http://upload.wikimedia.org/math/8/7/6/8762e7a22946ddf7f43688a492986920.png

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