[iiwusynth-devel] Filter (was: FluidSynth roadmap)

[M. Nentwig]

Hi,

this mail was trying to hibernate in the 'Drafts' folder, I just
stumbled over it by accident :)

> Maybe we are not talking about the same thing : i was talking about
> an adjustable band-pass filter. I was talking to Peter about it and
> he told me that it was not implemented yet. Maybe I should reread the
> documentation...

Currently there is only a resonant two-pole lowpass filter, 12 dB /
octave.
If you need a different filter (bandpass), then that needs different
coefficients, but the algorithm is the same (as long as it's not 18 or
24 dB / octave).
Replacing the lowpass filter with a bandpass filter is therefore easy -
it means just adding five lines of equations from Robert Bristol's
filter cookbook.
But I don't know how to integrate it into the synth (how to choose the
filter).
If you can find an example how it's done in some SF2 compatible
hardware, let's do it the same way.
Otherwise it could be easily done on a per-channel basis using the
settings system.

Of course you could also add the filter using the 'Ladspa' Fx unit, but
that's an entirely different story.

Cheers

Markus