[alsa-devel] how to handle buffer underrun in a softsynth

[Henning Thielemann]

I have written a software synthesizer in Haskell that fetches MIDI events 
from ALSA sequencer and plays the rendered signal via ALSA pcm. However it 
cannot cope correctly with buffer underruns.

I tried to learn the correct way from the miniFMsynth example of
    http://alsamodular.sourceforge.net/alsa_programming_howto.html
   however this program floods my terminal with buffer underrun messages 
without even being connected to any MIDI event source. This is independent 
from how large I choose the BUFSIZE constant.

I use:

$ pkg-config --modversion alsa
1.0.14

  Also, as far as I understand, that program allows to start notes only at 
block boundaries. This way it can ignore the timestamps of the incoming 
events. But this is crucial for me: I want to allow large blocksizes 
and thus I must allow notes to start anywhere inside a block.
  Now when I detect a buffer underrun on writing a block to an ALSA pcm 
sink, I like to know the time gap in order to adjust the timestamps of the 
incoming MIDI events.

My question in short is: Is there an example software synthesizer as 
simple as miniFMsynth, that works (on my machine), supports note start 
within a block and copes with buffer underruns in a reasonable way? If no 
working example, is there some documentation on how this is intended to 
work?


Thank you for your help
Henning