[music-dsp] Article: antialiased sine waveform syncing

Brian Clevinger brian at absyn.com
Tue Jun 9 09:36:37 EDT 2009


Maybe I am misunderstanding you, but it sounds like a type of granular  
synthesis. By allowing the slave(s) to ring and overlap you will get  
frequency dependent phase cancellation/reinforcement. It's a musically  
interesting effect, but it's different from syncing. But that depends  
on how much the ringing overlaps, maybe if it's short enough you won't  
get too much phase cancellation.

Perhaps what you're describing is similar to Xavier Rodet's FOF  
technique.

Brian



> On Tue, Jun 9, 2009 at 2:40 PM, Vadim
> Zavalishin<vadim.zavalishin at native-instruments.de> wrote:
>>> Now you filter this BLIT with the actual output of the slave
>>> oscillator (after reset).
>>> So consider the slave oscillator's output just an FIR filter. And
>>> let's take for example
>>> a sine slave oscillator for the sake of the conversation. Now, an
>>> infinitely long
>>> sine has a delayed (in frequency domain) impulse  as a frequency  
>>> response.
>>> However, a windowed period of a sine has a big fat lobe as a  
>>> frequency
>>> response centered at
>>> where the impulse would be in the infinitely long case. _This_  
>>> causes
>>> the harmonics
>>> from the BLIT to leak - we have to shrink that lobe and the best way
>>> of course is
>>> to give our sine some space in time. This generalizes analogously to
>>> arbitary waveforms.
>>
>> Right, but how can we give our sine some space in time in the  
>> context of
>> hard-syncing? The window size is pretty much fixed to the period of  
>> the
>> master oscillator, isn't it?
>>
>
> That's what erroneously the article suggests - and that's why it's  
> outdated.
> We have to let it ring more and of course increase overlapping and  
> complexity,
> but with hugely better numerical accuracy than the generalized BLEP  
> method.
> And it's really not that bad since with FIR interpolator for the BLIT
> is very vectorizable
> as i also describe in an earlier post.
>
> Now, the pseudo-C++ code i have in the article should make more sense
> to people also
> (it also hints some additional optimizations).
>
> However a good outcome is that even if you don't let the slave ring
> more you still
> get a harmonic output that doesn't alias because our BLIT takes care
> of that (that could be useful).
>
> Yours,
>
> George Bezerianos
>
>> Regards,
>> Vadim
>>
>> --
>> Vadim Zavalishin
>> Senior Software Developer | R&D
>>
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