[LAD] on the soft synth midi jitters ...

cal cal at graggrag.com
Tue Oct 5 13:05:00 UTC 2010

On 05/10/10 22:58, Clemens Ladisch wrote:
> cal wrote:
>> On 05/10/10 18:51, Arnout Engelen wrote:
>>> Latency? Or jitter?
>> Not sure - possibly the main reason for the post was to seek help in resolving
>> fallacies in my thinking. With a jack period of 128, a midi event associated
>> with frame 129 won't actually get applied to audio generation until the
>> generation of frames 257-384. On the other hand an event against frame 128 will
>> make it into the generation of frames 128-256.
> You seem to be assuming that when you are generating the sound for a
> period, and when you find a new event, you have to put the event's
> effect into the entire period, i.e., the event's note then starts at the
> start of the period.

In a perverse way, that's helpful - for me it confirms that I need to gain a
deeper & stronger understanding of zyn's current note on/note off processing
before I'm likely to achieve improvement.

> What you have to do is to remember the timestamp of the event (measured
> in frames, like above), and then apply the event at that time in the
> period that corresponds to the original time, relative to the period in
> which it was received.  From your example above, the audio data for the
> event received for frame 128 should start at the last frame of the
> period, i.e., frame 256, while the audio data for the event received for
> frame 129 starts at the first frame of the next period, frame 257.
> Jitter is defined as varying latency.  You can remove it by taking the
> worst-case latency (if it exists) (one period in this case) and applying
> it to all events.

All genuinely helpful, thank you!

cheers, Cal

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