RE: [iiwusynth-devel] FluidSynth roadmap

[Antoine Schmitt]

:::::::::21/11/02::::16:41 +0200::::address@hidden:::::::::
>  > Markus, you answered to me alone again... :-)
>
> Good point. I should CC to the list. But I want to maintain a 
> healthy rate between other people's mails and mine :)

You did it again ! :-) Maybe on purpose, but it seems that this is 
interesting to the list.

> >  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...
>
> 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).
> A bandpass filter itself is easy - add five lines of equations from 
> Robert Bristol's filter cookbook.
> But I don't have a clue how to integrate it into the synth (how to 
> choose the filter). It could be easily done on a per-channel basis, 
> but a better way would be to somehow put the information into the 
> soundfont.
> If you find an example of an existing product, it should be easy to 
> just copy the way it is implemented.

Ok, I RTFM and i get it: SoundFont only defines a low-pass filter, 
which CutOff freq and resonance could be controlled by a 
controlchange (through NRPR and such), but is normally controlled by 
LFO or envelope. I guess we'd better leave it the way it is.
And for a bandpass filter, I guess that we should preserve the 
SoundFont specs as much as possible, and maybe extend it by allowing 
more final effects like chorus and reverb : bandpass, equalizer, 
etc.. And this should be part of a larger scheme, which includes the 
already mentionned sound routing issue, Timidity, Jack, etc..

Thanks for enlightening me, I'm not a sound expert, I'm more an API guy...

++ as