| I think you are right about the fact that a big table can make multi-point interpolation
useless. Actually, in the case of a sine wave I find that even a 1024 point table, readed
by the oscili opcode, sounds very very good at any frequency. The problem rises when using
sound samples (for example with loscil). In this case the table is filled by a set of
samples already existent, and the user cannot modify them. Also in this case the computer
memory is not so big to expand the wavefile length and interpolate the samples by means of
good a wave editor.
BTW What is the difference beetween Sinc interpolation and polynomial interpolation
(excuse my math ignorance).
Gabriel
Larry Troxler wrote:
>
> A couple of observations/questions:
>
> - When I was using Csound, I would simply use a large enough table
> size, so that the error created by using only linear (or none at all)
> interpolation, was less then the resolution of the output file type (in
> my case, 16 bits). On today's machines, using 64K for a wavetable isn't
> a big deal. I suppose the tradeoff is that there the RAM cache will be
> overwhelmed on certain processors, hence making interpolation
> preferable.
>
> - At what point, does Sinc interpolation (which, is the theoretically
> correct approach) become more cost effective (in terms of fidelity per
> computation time) then polynomial interpolation? Without really
> analyzing the tradeoffs, my initial response to a proposal to a proposal
> to use say, eight-point poly interpolation, would be that surely a Sinc
> interpolation with lesser points would give better results. But perhaps
> not, especially given that the implementation of a Sinc interpolation
> might need to involve a second table lookup to efficiently compute the
> sinc function!
>
> Well, in summary, (a) Why not just use larger table sizes where the
> interpolation method isn't an issue, and (b) what are the tradeoff
> points with polynomial vs. Sinc interpolations?
>
> Larry
>
> -- Larry Troxler -- lt@westnet.com -- Patterson, NY USA --
--
Gabriel Maldonado
http://www.agora.stm.it/G.Maldonado/home2.htm |