AUMIDISynth + AUSampler: notes stop sounding past 14 simultaneous voices. Can I tweak the polyphony settings?
AUMIDISynth + AUSampler: notes stop sounding past 14 simultaneous voices. Can I tweak the polyphony settings?
- Subject: AUMIDISynth + AUSampler: notes stop sounding past 14 simultaneous voices. Can I tweak the polyphony settings?
- From: Archagon <email@hidden>
- Date: Tue, 01 Nov 2016 13:36:41 -0700
I've run into a pretty major issue with AUMIDISynth
(kAudioUnitSubType_MIDISynth) that I can also replicate in AUSampler.
In brief, I have an SF2 with some samples that play for several
seconds after touch-up, and if I play too many notes in succession,
new notes will simply fail to sound until at least one of the previous
notes has finished attenuating. My understanding is that standard MIDI
polyphony is supposed to "steal" an already-playing note when you go
past the polyphony limit. In AU Lab, using AUSampler, this works
correctly when the polyphony is set to 8. However, if you set the
polyphony to something like 32, the number of "voices" appears to be
capped at 14 and prevents any new keys from sounding past 14
simultaneously playing notes.
Here's a demo YouTube video: https://www.youtube.com/watch?v=69KkpKk0OlQ
Unfortunately, I can't find a way to adjust the polyphony or voice
count when using kAudioUnitSubType_MIDISynth in software, which means
there's no good way to prevent notes from failing to play past the
voice limit. Sending a Sound Off command does reset the voices and
allow me to start playing notes again, but this is a channel command,
so I can only use it as a crude bludgeon to turn off every note
simultaneously. I've considered several approaches to fix the problem
— creating a separate synth for each instrument and putting each note
in its own channel, creating a "double buffer" out of every two
channels and only sending Sound Off to a buffer when they switch, or
maybe just automatically sending Sound Off every 14 notes — but these
feel like hacks. Surely there's a way to get around the issue in a
more conventional way? It would be a shame if I had to code up a
complex meta-synth just because I couldn't tweak a symple polyphony
setting!
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