[fluid-dev] Questions about soundfont, voice rendering, pitch shift...

[jimmy]

Lots of questions.  If someone can answer just some of them, please do.  Some 
of these might be more than just Fluidsynth, but Fluidsynth is used to produce 
the final output and the notes don't sound too good for now.

I'm trying to make a soundfont from a single audio sample (somewhere between 
octave C3-C4).  The sample is about 4 seconds.  So it is set to the whole range 
of notes (0-127).

What happens is the lower octave notes seems to lose some volume.

More problematic are the upper octave notes, they sounded so short (1-2 
seconds, or less).  It may sound OK for short-duration sounds like like piano, 
xylophone, but for synth strings, sawWave, squareWave, pads...  It also sounds 
much less like the original sound.

I know that in pitch shifting, tempo can be kept constant, which also sound 
much closer to the original sound characteristics.  Some library, like:

   www.surina.net/soundtouch/
   
can do so and is part of apps like mhwaveedit, rezound, ardour, audacity...  I 
have tried on a whole song (non-realtime) in audacity and it sounds good.

So, I wonder if Fluidsynth voice rendering can be changed to keep the sound 
length constant (same as original sample)?  Of course, this is just some 
experiment for the time being.  Does anyone have time to look into it?  Or 
perhaps, give me some pointers as to where to look in Fluidsynth code so I can 
try it on my own?

Also, if original audio sample rate is 192 kHz, with jackd and fluidsynth run 
with 44.1 kHz, does Fluidsynth scale the sample to the appropriate pitch using 
192 kHz, then resample to 44.1 kHz?  Or, how does Fluidsynth do that right now? 
 What's recommended in this case to get better sound out of a single sample to 
be use as the only sample for all 128 notes?

Thanks,

Jimmy