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differentiated polynomial waveform oscillators

December 15, 2012 | 1:58 pm

a couple of quasi-bandlimited oscillators. Not particularly efficient, but perhaps some interesting VA waveforms can be achieved

Attachments:
  1. dpwosc.zip

December 15, 2012 | 7:17 pm

Thanks for these Oli. Making band limited oscillators in Gen is something I need to be able to do soon. Can you talk about this method or point to some literature?

Thanks,

Dave


December 15, 2012 | 9:09 pm

I believe Oli’s patchers are using oversampling to reduce the aliasing artifacts of digital waveforms. The advantage of oversampling is that it can be used on any waveform generator, but the amount of oversampling required may vary by waveform, and by what is an acceptable noise floor vs. performance tradeoff.

There’s a couple of alternative approaches to band-limited oscillators in the gen~ examples folder, one using Discrete Summation Formula BLITs, and the other using feedback FM. Both have their strengths & weaknesses too. The feedback FM is pretty cheap, but the aliasing is reduced but still present. The DSF BLIT is more involved, but is certainly cleaner.

I started working on a minBLEP based oscillator example, but it’s not working yet.


December 16, 2012 | 12:24 am

Cool, I was aware of the FM technique from this paper

http://www.acoustics.hut.fi/dafx08/papers/dafx08_05.pdf

…but somehow missed the Gen examples.

Thanks


December 16, 2012 | 1:34 am

the patch I posted is 8x oversampled. I think that a higher order DPW could produce better results without such heavy oversampling.
The paper "Alias-suppressed oscillators based on differentiated polynomial waveforms" explains more about this technique as does "Digital Sound Generation" from ICST

- would be interested to see the gen~ minBLEP when it is done.


December 16, 2012 | 2:22 am

Thanks for the reference to the IEEE paper Oli.


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