Re: [Linuxsampler-devel] envelopes, events, Re: LS click/pop investigation

[<be...@ga...>]

> > 
> 
> a lowpass filter with just a pole:
> 
> y[i] = (x[i]-y[i])*c + y[i];	//x[i] is just a gate signal - 1 to turn
> the env on, 0 to turn it off
> 
> a linear segment:
> 
> y[i] = y[i] + k;
> 
> the lowpass filter costs you an extra add and multiply compared to a
> linear segment, not much really. the trouble with the linear segment
> method is that to approximate a log segment you have to do a fair number
> of linear segments. it's the computation of a segments 'k' and how long
> each segment must last to approximate the log shape that i believe will
> make it more expensive when compared to the lowpass approach which does
> the right shape in one segment with one coefficient. 

It depends what the user wants.
For example do we want changing the enveloping information in real time ?
Do other samplers permit this ?
We could precompute dozen (or 100) of linear envelope segments resembling
arbitrary curves and switch the tables in real time (at note-on time) without
any overhead.


> the only problem
> with the lowpass approach is that it needs a tiny little bit of work to
> guarantee that it is at maximum in a certain time, and to guarantee it
> is off after a certain time. they are pretty trivial modifications
> though.
> another issue to consider is that the slower your attack time is, the
> more segments you will need to use to approximate it without it sounding
> bad.
> so, i would say if you want a log envelope, use a real log evelope
> generator, as it will make life much much easier.

performance = 90% of life :-)
I'm still not convinced if we should go the log route.
Let's see what others say.

cheers,
Benno
http://www.linuxsampler.org


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