[LAU] Fluidsynth, soundfonts, jack, and latency

[Dominic Sacré]

On Monday 02 of November 2009 14:42:43 Guru Prasad B. R. wrote:
> Second issue of note: few weeks ago, while still running Ubuntu, I
> wanted to find out what exactly caused the jack crash that I reported
> on this list at the time (perhaps unrelated to the current issue) . I
> found a "stress test" to replicate the problem: hitting a lot of
> notes while keeping my sustain pedal down. Initially, the crash would
> happen within 20-30 seconds of banging the controller (!). When I
> changed the polyphony settings from 256 to 64, it would be much more
> stable - for more than 10-15 mins of banging! Again, I was able to
> replicate the same thing with ghostess.
>
> This incident has left me with a lurking suspicion about a possible
> bug in the fluidsynth libraries. I'm curious, though... has anyone
> else experienced similar issues?

I also have some problems with fluidsynth causing very high CPU load. I 
normally run ghostess with fluidsynth-dssi, but I'm pretty sure it's the 
same with other fluidsynth frontends. It's interesting that fluidsynth's 
CPU load is in many cases much higher than that of linuxsampler, for 
example.

Also, what exactly does the polyphony setting in fluidsynth mean? Do 
soundfonts have multiple layers which all use up polyphony? That would 
be the only explanation I have for how easily I can exceed the available 
polyphony (without even using the sustain pedal). But on the other hand, 
most soundfonts sound rather plain, so something doesn't seem right 
there... Where are all my CPU cycles going?


Dominic