Re: [Linuxsampler-devel] GigaStudio LFO compatibility

[Ivan M. <iv...@ma...>]

On 26/09/2019 14:32, Christian Schoenebeck wrote:
> Hi all,
Hi Christian,
>
> I was reviewing our gig engine's LFO code and noticed that their behaviour
> does not match with GigaStudio's original LFO behaviour. So I planned to
> change that:
>
> 1. Our gig engine is using triangle LFOs whereas it looks like GigaStudio
>     actually had sine LFOs. So my plan is to make sine to become default and
>     make triangle available as option instead (as part of a new gig file format
>     extension). Looks like GSt only ever had one function type (sine) for LFOs.
Many thanks for discovering this.
>
> 2. Start value of unsigned LFOs (which are amplitude LFO and filter cutoff LFO
>     in the gig engine): I see that our implementation of those 2 (unsigned) 	
> 	LFOs start with wrong initial values; the very 1st rendered sample is 0 and
>     then the function jumps to the middle of the value range and continues from
>     there. That initial jump is certainly a bug that should be fixed. But what
>     about the actual start point; does anybody know whether GSt starts with
> 	a) zero, or b) mid value range, or c) max. value on those 2 LFOs (amp LFO &
>     filter cutoff LFO)?
I checked the GSt3 editor and its audio window indicates that LFOs 1-3 
start with the mid value. Seeing as the wave-forms in this window appear 
to be accurate representations of audio file contents and LFO settings 
the phase information should be accurate also.
> A start phase option for our LFOs (as format extension) might make sense as
> well BTW.
This sounds like a good idea.
> CU
> Christian

All the best,
Ivan