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Re: [fluid-dev] SoundFont parameter analysis

From: Tom M.
Subject: Re: [fluid-dev] SoundFont parameter analysis
Date: Thu, 21 Jun 2018 19:48:54 +0200

> The spec says additive, not multiplicative. Unless I'm missing something?

Additive, because the spec assumes all times to be in absolute timecents. 
Soundfont editors however report values in seconds for instrument generators 
and a multiplicative factor for preset generators. So your calculations are 
basically correct, but they have to be done in SF2 native units. In case you're 
fancy for math:

seconds = 2^(timecents/1200)

Let "tci" be the absolute timecents of the instrument generator and "tcp" the 
realtive timecents of the respective preset generator:

2^( (tci + tcp) / 1200 ) == 2^( tci / 1200 ) * 2^( tcp / 1200 )

Where the left hand side is what the spec suggests and the right hand side is 
my previous showing.

> > The modulation in this case affects the filters cut-off freqency. Thus it 
> > needs 7 seconds for the filter to fully open. This is pretty much what I 
> > hear. Dont know about the 1.5 sec you refer to.
> Just what I heard Vienna do, and I consider that the gold standard since Emu 
> created it at the time SoundFont was designed. But 7sec is closer sounding 
> that 60ms =)

I see. Vienna probably uses the convex modulation env., i.e. the correct one, 
so the filter is almost open after 1.5 sec., however it takes another 5.5 sec. 
to really fully open to the last Hertz, which is however pretty inaudible in 
this case.


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