Re: [fluid-dev] Major degradation in sound quality & cpu usage going from Ubuntu 11.04 to 11.10

[David Henningsson]

On 2011-10-28 03:09, Aere Greenway wrote:
> David:
>
> I downloaded the source for the older level of FluidSynth, but didn't
> know how to build it.
>
> But I remembered the file structure in Unix (and Linux), and looked for
> the executables in /usr/bin.
>
> I use qsynth (which uses FluidSynth). On finding it in the Ubuntu 11.04
> system, and in the 11.10 system, I substituted the different executables
> in each system, and what I found was surprising, from the symptoms I had
> observed.
>
> First, the old version (from 11.04) of qsynth on Ubuntu 11.10 also
> failed. The new version (from 11.10) on 11.04 worked fine.
>
> I therefore conclude that the cause is in Ubuntu 11.10.

Ok, so this is completely wrong. First, FluidSynth's main functionality 
is in a library (.so) file, so you have not changed FluidSynth by just 
moving the executables. Second, while ABI breakage is quite rare these 
days, subtle library differences can still make moving files between 
distro versions fail. Recompiling the program on the distribution you 
want to run it on (or in pbuilder, but that's a separate story) is both 
easier and gives correct results.

Here is a mini-howto for how to do that on Ubuntu. Let's assume you have 
a directory ~/fluidsynth-code, you are in Ubuntu 11.10 and want to 
compile FluidSynth 1.1.3. First download the source, e g from launchpad 
by going to https://launchpad.net/ubuntu/+source/fluidsynth, click the 
arrow for the selected version, then click to save the files ending with 
".dsc", ".debian.tar.gz" and ".orig.tar.bz2".

Then execute the following commands:

cd ~/fluidsynth-code
dpkg-source -x fluidsynth_1.1.3-3.dsc
cd fluidsynth-1.1.3
dpkg-buildpackage -b

This will create files named "fluidsynth_1.1.3-3_i386.deb" and 
"libfluidsynth1_1.1.3-3_i386.deb" in the ~/fluidsynth-code directory. 
(Or amd64 instead of i386, if that's what your machine is running.) 
There will also be a libfluidsynth-dev_1.1.3-3_i386.deb", but you don't 
need that right now. Now run

cd ..
sudo dpkg -i fluidsynth_1.1.3-3_i386.deb libfluidsynth1_1.1.3-3_i386.deb

...to install you new packages. After that, just restart qsynth or 
whatever program is using fluidsynth, and test.

To return to the distribution supplied version again run "sudo apt-get 
install fluidsynth libfluidsynth1"

> Perhaps the path-lengths with interrupts locked out are too long.
> Perhaps something is causing problems by other means.
>
> What I notice on 11.10 (also with the old version of qsynth), is that
> everything seems fine until I try playing one of my sequences with many
> parts, and many simultaneous notes. Within about 30 seconds, things 'go
> bad', and stay bad. After that point, even simple sequences play poorly.
> Even playing notes on the keyboard is bad.

This sounds similar to a bug fixed a while ago, here: 
http://sourceforge.net/apps/trac/fluidsynth/changeset/435/trunk/fluidsynth/src/synth

// David