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Old 03-18-2019, 04:52 AM   #22
ovnis
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Urs :

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Well, I'm not sure how other developers handle this, but typically digital synths run modulations at control rate. That is, they update them (envelopes, LFOs etc.) every 16 samples or so. Some even do chunks of 64 or more (I guess that's what Reaktor's "800Hz" setting is for instance). Anyhow, we do a control rate of 16 samples for all MIDI events.

Now, with that in mind, the control rate sets the granularity at which events occur, such as note ons and stuff.

With a control rate of 16 for events, the best timing is achieved by distributing those events to +/- 8 samples of where they occur. It is IMHO the best way to deal with the issue of control rate vs. sample rate. It's still an order of magnitude more accurate than MIDI ever was.

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That said, I have sometimes thought about adding per-voice delays such that each voice could have it's output shifted into sync of the control rate with the MIDI notes. But this of course then only works for the Note Ons and not for the Note Offs, which would then possibly jitter even more. Not sure if that's of any benefit.

Our latest efforts go into reducing the control rate for events to 4 samples. This is also the control rate at which we process internal modulators other than MIDI. This is what we've done in Repro for instance, which should process with an accuracy of +/- 2 samples.

Quote:
That's not the reason for the PDC. The actual reason for the PDC is that we internally process everything in chunks that are a multiple of 16 samples. This lets us reduce CPU by a large factor.

PDC is not necessary if the DAW also uses buffers which are a multiple of 16 samples length, such as 64, 256 or 512. In that case, in our most recent synths PDC can be switched off (not in Tyrell N6 though).
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