[Linuxsampler-devel] Experimenting with sinc-based resampling

[JP C. <jp...@ci...>]

Hi, lately I've stumbled upon an old article that sings praise of
Akai S1000 samplers and the resampling algorithm it used.
This piqued my curiosity and inspired me to try implementing a sinc
resampler into LS for comparison.

I attach my code to the message, as patch against svn trunk.
Link to the article: http://martin78.com/samplers/akai-s1000-s1100/

-- some implementation notes:
* this is a N-point sinc resampler, where N is defined in code by
  parameter SINC_NPTOTAL=SINC_NPBEFORE+SINC_NPAFTER
* code uses optimization to reduce the number of trig operations/sample
  from N sin() to 1 sin() + 1 cos()

As default I have used parameters NPBEFORE=1 NPAFTER=7, the number of
past and future samples used respectively.
This happens in some situations, with some samples of my set, to crash
LS with segfault, presumably because of out-of-bounds access by
getSample().

The question is: where in LS is defined how many past/future samples are
available to the resampling?
I note LS already has linear and cubic which require 2 and 4. How
to control this number? Akai S1000 supposedly has N=8, but I'd like to
also to try larger lengths.