[sdiy] software / firmware envelopes in C (or anything else)

[Roman Sowa]

W dniu 2025-11-06 o 11:45, Gordonjcp pisze:
>> Anyway, I do it exactly like in your equation. Target is changing between 0,
>> full scale and sustain level, depending on ADSR phase.
> 
> Ah - you have to watch that!

no, I don't, because it works :)

> 
> You've got to flip to the decay phase at somewhat less than full scale because the "RC network" charges asymptotically to the rail.

and I do, I didn't say at which point though. Target is at full scale, 
attack trigger point is at half scale. TBH this is still not all I do 
there, but for the sake of discussion this is enough.


> 
>> All done in fixed point math, but 24 bits is a must, as 16-bit truncation
>> errors spoil the ends of decaying phases.
> 
> Can't say I've noticed this.

Probably because you are neurotypical person. I feel sick if the 
envelope doesn't decay within 16-bit 1LSB of the destination I want it 
to go.


> The Juno 106 has roughly half its voice ROM full of such tables, just to make the controls work nicely ;-)

and to avoid complex, repeating calculations, given that every 
instruction of processor time is precious.