[Linuxsampler-devel] Gigasampler filter reengineering

[Christian S. <chr...@ep...>]

Hey guys!

As you probably know, we finally made big advances in finishing a first engine 
providing gig playback. Benno and I are currently just making final 
optimizations and corrections. It will first only allow simple sample 
playback, but I'm already looking ahead to complete it with full support of 
all articulation data the gig format offers. For that we need somebody with 
access to a running Gigasampler/Gigastudio installation to record some 
samples using Gigasampler's filter, so we can choose VCF algorithms that come 
as close as possible to the original filter characteristics. You don't have 
to be an DSP expert to do this, nor is it a hard task.

This is what you have to do: Take the following samples which Benno already 
prepared for you:

	http://www.linuxsampler.org/peakwavs.tar.gz

These are two samples; one stereo, one mono. You can choose between one of 
them. These samples are short pulse samples, means null samples with one 
hard, straight flank. Create a new gig instrument in Gigasampler's instrument 
editor and import the wave. Create a region in the instrument, so you can 
actually play the sample. Make sure that the sample will be played as is, 
means use a dry, hard amplitude envelope (most important an attack time of 
0.0s), stuff like LFOs and of course effects etc. all turned off, activate 
the filter using fix values for resonance and cutoff frequency, play the 
sample and record the output. Do this for different values of cutoff and 
resonance, where you can do discrete steps of e.g. 16 or 32, choose it 
yourself, but note: it's important that you play the sample by it's original 
sample frequency, so trigger the sample by it's root note (a.k.a. unity note) 
only and be sure there's no fine pitching set or something like that, else 
Gigasampler's interpolator could wash away the hard flank we need. You could 
make samples with following values for example (resonance, cuttoff):

	(0,0),(0,32),(0,64),(0,96),(0,127),
	(32,0),(32,32),(32,64),(32,96),(32,127),
	(64,0),(64,32),(64,64),(64,96),(64,127),
	(96,0),(96,32),(96,64),(96,96),(96,127),
	(127,0),(127,32),(127,64),(127,96),(127,127)

Repeat that for the 5 filter types Gigasampler provides: Lopez, ... no just 
kidding: lowpass, lowpass turbo, bandpass, highpass and band reject.

And finally let us get your samples somehow.

It would be great if somebody could do that!

CU
Christian