Re: [fluid-dev] Thread safety

[josh]

Hello Jimmy,

The current design of FluidSynth is that the synthesizer runs in the  
audio thread, there is a MIDI thread and the main thread for the  
fluidsynth shell.  The audio thread synthesizes active voices to the  
audio stream.  Events received by the MIDI thread activate/deactivate  
voices based on note on/off events and change voice parameters via  
controllers, etc.

Currently there exist mutual exclusion issues between threads which  
create MIDI events and the synthesizer thread.  Either proper mutex  
locking needs to be implemented or the code must be serialized in a  
way, where locking is not needed.  What David is proposing is the  
latter.

The only real parallel execution benefit that FluidSynth currently  
has, is that calculations related to incoming MIDI events occur in  
parallel with the audio synthesis processing.  If all this could occur  
in one thread and the MIDI events could be processed while waiting for  
the next playback audio buffer to be ready, then David's proposed  
single thread synthesis architecture may actually be more efficient on  
a single CPU system.  I think this may be hard to do though, since the  
various execution models of the audio drivers (Jack versus ALSA for  
example), make it difficult to process the MIDI events while waiting  
for the next audio buffer "fill" event.

These changes should not affect functionality as seen by external  
software using FluidSynth.  At least that is the goal.  So rest  
assured, that whatever final resolution we choose, FluidSynth should  
be more stable, with a minimal amount of added overhead (if any).

Best regards,

Josh


Quoting jimmy <address@hidden>:
> Some more questions for David,
>
> I don't know of the FS internal threading code or David's propose   
> changes.  But let me ask if the change may affect apps that use 32,   
> 48, 64, or more channels?  There are some apps that use such   
> features in FS.
>
> Along with that, what about cases of running multiple apps and   
> multiple hardware sequence players (drum machine, background   
> sequences, and midi keyboards... at the same time) that connect   
> through jackd to FS playing in live (in real time, low-latency)?
>
> Jimmy
>
>
>
>
>
>
> _______________________________________________
> fluid-dev mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/fluid-dev