I'm running into this issue again in iOS 14.0. This time it's not crashing or logging a message, but the audio thread is stuck in an infinite loop when playing a note.
The audio thread hangs and never returns from AudioUnitRender, and stopping the app at various points shows a stack trace in various calls below SamplerNote::Render but never above it.
The issue seems to relate to the envelope parameters & the timing of the note start & stop events. For example:
Given a DAHDSR envelope described as: (D:0, A:0, H:0, D:0, S:0, R:0):
A 32nd note at 104-123 BPM (note durations of 0.06097561s-0.072115385s) with envelope (D:0, A:0, H:0.06 D:0, S:0, R:0) will hang after playing a few times. Changing the Hold to 0.5 causes "bad BPMs" to move to 120-149 BPM (0.05033557s-0.0625s). Changing other envelope parameters to be > 0 also seems to cause the issue to go away but there is no clear pattern or guarantee that it's fixed for all BPMs/note durations.
This issue is not reproducible on iOS 13 and macOS 10.15.6.
jayson
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