Re: [fluid-dev] sequencer / synth bug ?

[Josh Green]

Hello Antoine,

On Wed, 2007-05-02 at 11:07 +0200, Antoine Schmitt wrote:
> Hello,
> I've got a strange issue, and I don't know if it comes from the  
> sequencer, from the synth, or if it is 'normal'.
> 
> Context : it's using the fluidXtra, which I've built on top of  
> fluid-1.0.5, on MacOSX and Windows. A user of mine has built a midi  
> interpreter on top of this, in Director/lingo, parsing midi files and  
> playing them through fluid _but_ not using the fluid midi-file  
> playing features (because he changes the midi on the fly). He uses  
> the fluid sequencer to schedule the midi events.
> 
> The problem: some notes are not played. After some searching, it  
> boils down that some drum notes have a duration of 7 ms : the noteoff  
> happens 7 ms after the noteon. These notes are not always played  
> (heard).
> 
> I'm not sure if this is normal (delay smaller than buffersize or  
> something), or if this is not normal (it does not see normal).
> If it is not normal, where is the problem : in the fluidsynth or in  
> the scheduler ?
> 

The FluidSynth buffer size is 64 samples, which at 44100 is about 1.4ms.
7ms seems like a very brief amount time though, so a question I have is
if the sound is indeed meant to only last 7ms, or if it is being used
more as a trigger.  If the release time of the volume envelope for the
percussion instruments was increased, and the problem goes away, this
might be the issue (note off is immediately turning off the voice).

There are also sometimes issues with the voice stealing in FluidSynth.
If it is approaching the maximum number of voices, sometimes the
priority of which voices get killed is not quite right.  This needs to
be fixed and could also be the problem.

> I've attached the midi file in question. For example, at the  
> beginning of the file (after about 1 second), there are 4 notes 70 on  
> channel 10. Their duration is 7 ms. With my setup, sometimes one of  
> the notes does not play. There is also a drumroll a bit later (after  
> 4 seconds or so). This drumroll is really broken in my setup (most of  
> the notes don't play).
> But if I play this file in Quicktime player, there is no problem :  
> all notes are played.
> 

That MIDI file was too big for the current mailing list settings.  I can
put it on my web server for others to download if needed, just ask me.

> Any hint ?
> thanks a lot
> 

Perhaps that helps?  Unfortunately I don't have a lot of time right now
to investigate the problem more thoroughly.

Cheers.
        Josh