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[fluid-dev] Problem with Fluidsynth and looping

From: Tomas Nykung
Subject: [fluid-dev] Problem with Fluidsynth and looping
Date: Mon, 21 May 2007 10:17:40 +0300
User-agent: Mutt/1.5.13 (2006-08-11)

Hi everyone.

I'm a jOrgan user, http://jorgan.sourceforge.net
using Linux (Debian) and Fluidsynth as an virtual pipe organ.

We "jOrganists" (I'm not alone with this problem) have a problem with
Fluidsynth and looping.

The problem shows up in soundfonts that have real samples of real pipe
organs. In a pipe, the sound isn't steady, -the sound varies slightly
with time, and therefore the looping point is very critical. If the
looping point is off, even just a little, then you get a "click" sound
every time the sound loops, and this is exactly what happens with

I had never noticed this problem before, when I used soundfonts such as
the Jeux soundfont, http://members.aol.com/realmac/jeux1.htm
that have very small samples, but when I last December bought the
Marcussen soundfont from http://www.solcon.nl/ahoogendijk/index_uk.html
then the problem became very annoying.

We had a long thread discussing this problem on the jOrgan mailing
list, as there was another user that also had this problem with his
own soundfont(s), and then I got the "bright" idea of adjusting the
loop points of every sample with Swami.

I was just stumbling in the dark, trying anything that maybe could
help with the problem, and eventually found that adjusting the loop
point exactly two steps downwards in every sample in the whole
soundfont fixes the problem!

Just to be very clear about what I'm speaking about:
See the red arrow, I adjusted this value exactly two steps downward
in every sample.

The problem with this "correction" of the soundfont, is that there
isn't a problem in the soundfont itself, it's perfectly looped, so this
"correction" only works around the problem in Fluidsynth, and after
this "correction" is applied to the soundfont, the soundfont sounds
wrong when played in any other sampler, be that a SoundBlaster Live!
hardware sampler or sfx or whatever!

As the Marcussen soundfont is proprietary, I can not send that to
anyone, but I got another user to send me an example of his soundfont
to illustrate the problem, and for testing.
It is just a very small example soundfont, one octave of
Great Fifteenth 2' stop, and one actave of Swell Clarion 4' stop, but
it's enough to illustrate the problem.

Here is a demo of what it sounds like before the "correction",
Clarion 4', note e4:

and here is the same note, played after adjusting the loop point:

Here is the original soundfont, before I "corrected" it:

And here is the same soundfont after the "correction" is applied with

I think (but I may be wrong) that there is some kind of "off by two
points" bug in the Fluidsynth loop handling(?) that doesn't show up
with "normal" soundfonts, so therefore nobody noticed the bug before.

If anyone could look into this, then I would wholeheartedly thank them
from all us virtual organ players that wants to use Linux and

If you need more info / testing / whatever then just ask, I'm here.

Regards Tomas Nykung

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