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Better antialiasing wanted

Posted: Sun Feb 17, 2008 1:41 pm
by Shy
Devastor does have good antialiasing, but not good enough. Like all other software disortion effects, it sometimes ruins sounds that have sharp transients. A good example is synth sounds such as saw wave with some filter resonance.
I've made a little example to demonstrate the artifact. The left channel is without devastor, the right channel is with it. I intentionally used very subtle settings in Devastor to keep it very close to the original sound to have a clear example. With higher preamp gain the effect of course increases.
It decreases when I use 96KHz, but still there and annoying, and working at 96KHz is not really an option anyway. So I hope you can improve this, maybe add a higher quality antialiasing setting. I know it will use much more CPU. I don't care, I'd just like no noticeable aliasing.

Posted: Mon Feb 18, 2008 12:37 am
by Shy
Just in case anyone didn't fully understand the severeness of the issue, here is another example, Devastor on left channel. My Nord Rack (used for this demo with extreme filter resonance for clearness) and SH-101 absolutely hate digital distortion effects as you can hear. All because of damned aliasing. Make no mistake, other plugins are actually much worse with this sample and others like it.

I know you D16 guys have made it a major goal for yourself to have very good antialiasing for Devastor, but as you can hear it's definitely not there yet after all. The artifact by aliasing is also really horrible on sharp synth kick drum sounds, making them completely unusable. Again, not differently from any other software distortion effect I know.

So it may be good enough for not very demanding audio, but I deal with mostly really demanding synthetic sounds so it's especially important to me. I hope you can improve it. Thanks.

Posted: Tue Mar 04, 2008 4:06 am
by blacker
The second example makes my brain hurt. I haven't managed to get any alising going on in Devastor so far, but I don't use sounds that are quite so high pitched and rezzy as that one, I guess.

Posted: Tue Mar 04, 2008 9:59 am
by Jacek@d16
Hi Shy,

below is a spectrum of the first sample. As You can see the sound harmonics drops down over 17kHz drasticaly. Antialiasing here is even better than Your sampled synth ;)

For the second sample... hmmm i must see Your Devastor setup. Please post here the preset xml please. It's very important, because the diode clipper itself can't produce such aliasing...

Ofcourse we can improve it.


Posted: Sun Mar 09, 2008 10:11 pm
by Shy
I don't know what you mean by "better than the sampled synth", there is obvious, audible aliasing by Devastor, a visual analysis is not needed to know that. The second sample just demonstrates the aliasing more drastically. You can produce very audible aliasing with Devastor yourself very easily with the samples I provided (use the unprocessed channel).
the diode clipper itself can't produce such aliasing...
It can and it does.

Here is an SH-101 (so you know there's no aliasing of any kind). One sample without Devastor processing and one processed with it demonstrating the aliasing much more drastically than the previous two examples, to remove any doubt you may have.
Here is the simple patch I used, doing nothing except tweak the preamp amount in the aliasing example. The result is the same with any host. Try it.

Posted: Mon Mar 10, 2008 1:50 pm
by Jacek@d16
Shy wrote:I don't know what you mean by "better than the sampled synth"
I was just kidding :)
I know exactly what You mean. I'm working with it now. Probably we'll add an option for QUALITY. I think that max of 16x oversampling should be enough. We'll see...

Thanks for the samples.


Posted: Mon Mar 10, 2008 2:13 pm
by Shy
Oh, OK, my humor sensor was broken.
Looking forward to it, thanks.