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

cal cal at graggrag.com
Tue Oct 5 04:12:12 UTC 2010

I'm writing on behalf of a friend who's having trouble dealing with midi
latency in a soft synth (possibly yoshimi) ...

Given a jack period of N frames, the midi latency with the original code
effectively ranges from N frames to 2 * N frames, which I guess qualifies
it as jittery. So far my friend has tried a few things, but there's no
workable solution as yet.

What seemed most promising was to break the audio generation into smaller
blocks, applying pending midi events between blocks. Sadly, that drags the
creation and destruction of note objects into the realtime jack process
callback path. Latency improves, but the number of notes you can get
away with before it all falls in a heap is significantly reduced.

Getting the destruction of dead notes out of the realtime path is trivial,
not so the creation of new ones. Even with a pool of pre-allocated note
objects, it seems the amount of initialization code per note is still a
real limiting factor on how busy things can get before it all falls apart.

Such is life (for my "friend").

cheers, Cal


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