I'm back at testing!
I succesfully built fluidsynth with sdl2 backend. Latency is much better than with the OSS backend, but still not satisfactory compared to what I get with JACK on FreeBSD and Linux.
I used the following configuration:
fluidsynth -a sdl2 -r 96000 -o audio.period-size=64 -o audio.periods=2 -o audio.realtime-prio=99 -m oss -o midi.realtime-prio=0 -o midi.oss.device=/dev/rmidi1
If I set midi.realtime-prio to anything else than 0, I get the following message:
fluidsynth: warning: Failed to set thread to high priority
Maybe the remaining latency comes from the MIDI side. Is there a way to enable realtime priority for MIDI?
I also tried using JACK, but I failed to get any sound.
sun_driver: running null cycle ... don't know if that's relevant.
Does JACK work for you? If yes I'd be interested in the settings you use.