[iiwusynth-devel] dropouts help

[Antoine Schmitt]

Hi,
we are having some problems with the Win32 FluidSynth, on specific 
hardware. I would like to understand how to deal with it. Maybe some 
of you will have some idea.

The problem : dropouts when playing a noteon, on some 
looped-sustained organs. It is dropouts, i.e. like if the needle 
jumped to another place on the record, *not* a click where the sound 
continues playing with the right timing after the click. Depending on 
the buffer length, there are from an average of 5 dropouts per second 
(normal bufferlengths) to 1 every 5 or 10 seconds for largest 
possible buffer lengths. The rate of dropouts is not fixed. It varies 
depending on machine load, and even on mouse activity sometimes.

The hardware : SoundBlaster Live Value, Pentium III 1GHz Dual 
Processor, Windows2000, DX8
Note that it does not happen with a regular "SoundBlaster Live", on 
the same machine.
We have not tested yet with the LiveValue on another machine. We have 
not tested yet with another LiveValue card than this particular one.

We tried many buffer lengths (audio buffer, synthesis buffer), up to 
the maximum accepted lengths (without recompilation):
- synthesis = 512, audio = 32x512
- synthesis = 64, audio = 512x64
- synthesis = 128, audio = 128x64
The rate of dropouts was mostly sensitive to the length of the audio 
buffer, but was still sensitive to the synthesis buffer as well.

We tried using the commandline application provided with the standard 
source tree : iiwusynth, as well as with the Director Xtra linked 
with the iiwu library.

Any idea would be really welcome. Thanks in advance !



++ as