If you have not seen this before, there is a little trick I use for my old slow netbook -- halving the sample rate with the flag '-r22050'.
http://sourceforge.net/apps/trac/fluidsynth/wiki/ExampleCommandLines On Mon, May 28, 2012 at 6:09 PM, Aere Greenway <a...@dvorak-keyboards.com>wrote: > ** > Pedro, and all: > > It's interesting from your point of view, that the problem happens on > older, less capable machines, because of their floating-point handling, as > well as because of having to reduce the polyphony to avoid excessive > processing overhead. > > So I guess the older machines get hit by it both ways at once. I know of > the problem because I actually test my courseware on older, less capable > machines. > > It is actually a promotional point for my offering, that you can take a > machine that is gathering dust in the basement (because it won't run modern > versions of Windows), and turn it into a wonderful music workstation. > > I can still demonstrate this successfully using a 450 megahertz HP Vectra > machine with only 384 megabytes of RAM. > > As I think more about the problem, from what you said, I wonder if the > problem I noticed, and the problem you reported (that David fixed), are > actually the same problem. Perhaps it was something else fixed in that > later version that fixed my problem. > > I observed my problem on faster, more capable machines as well. It > definitely happened on my Dell Dimension 1100 machine, which has an > Intel(R) Celeron(R) CPU of 2.53 gigahertz. > > I also observed that applying the re-packaged (altered > version-designation) PPA fix (originally for Ubuntu 11.10) solved the > problem, in that the very poor quality sound (where random new notes are > dropped altogether, or sound only very briefly) does not occur with the PPA > version of libfluidsynth1. > > The problem also happened on my Acer Aspire laptop (which has two Celeron > (R) processors of 2.0 GHz, but uses 64-bit architecture. That was observed > on Ubuntu 11.10 (I have not yet converted that machine to 12.04). Again, > the PPA fix (which was just a later version of libfluidsynth1), made the > problem's symptoms no longer appear. > > In fact, none of the machines I own - even the fastest and most capable, > are immune from the problem. > > But that being said, I tend to purchase computer hardware from the > trailing edge of the technology curve, and Linux has prolonged their > usefulness - perhaps indefinitely (though with some of the later releases, > I am beginning to have my doubts). > > - Aere > > > On Mon, 2012-05-28 at 15:56 +0200, Pedro Lopez-Cabanillas wrote: > > Hi, > > On Wednesday 23 May 2012, David Henningsson wrote: > > FluidSynth upstream) didn't make a bug fix release either. Perhaps we > > should do that some time soon...so that the fixes will go into 12.10 at > > least... > > I'm not sure if only fixing that particular bug justifies a release. It > doesn't harm to do it, of course. But we may face very similar bugs in the > future. Let me explain. > > I've found the bug you are talking about some time ago, while I was working > with fluidsynth for a Nokia device having an ARM > processor:http://sourceforge.net/apps/trac/fluidsynth/ticket/100 > > This bug was solved by David with this > patch:http://sourceforge.net/apps/trac/fluidsynth/changeset/435 > > The problem was very specific to lowering the polyphony, but the cause was not > uncommon and had plagued FluidSynth for a long time. The root problem is > denormals in floating point > calculations:http://en.wikipedia.org/wiki/Denormal_number > > To show a similar problem, here is a simple test scenario. > > 1.- Sample MIDI file: http://www.miditrax.com/Aug/salsa.mid > 2.- GeneralUser GS Soundfont: http://www.schristiancollins.com/generaluser.php > 3.- Build FluidSynth (SVN head, or any previous release) in debug mode with > floats instead of doubles and FPE checks: > > $ cmake -DCMAKE_BUILD_TYPE=Debug \ > -Denable-debug=on \ > -Denable-floats=on \ > -Denable-fpe-check=on > > Runtime results on an AMD Athlon(tm) XP processor: > > fluidsynth: warning: FPE exception (before or in voice_write vol env): > Underflow > fluidsynth: warning: FPE exception (before or in voice_write vol env): > Denormal number > fluidsynth: warning: FPE exception (before or in voice_filter): Underflow > fluidsynth: warning: FPE exception (before or in voice_write vol env): > Denormal number Underflow > fluidsynth: warning: FPE exception (before or in voice_write vol env): > Denormal number > fluidsynth: warning: FPE exception (before or in voice_filter): Denormal > number Underflow > > When running FS in some old CPUs, denormals penalize CPU performance and sound > quality, while in modern CPUs these denormal numbers are automatically fixed > in hardware, eliminating the problem. > > My oldest machine is the only one I can access today, which is (slightly) > affected by denormals in FluidSynth: > > $ cat /proc/cpuinfo > processor : 0 > vendor_id : AuthenticAMD > cpu family : 6 > model : 10 > model name : AMD Athlon(tm) XP 2800+ > stepping : 0 > cpu MHz : 2086.903 > cache size : 512 KB > fdiv_bug : no > hlt_bug : no > f00f_bug : no > coma_bug : no > fpu : yes > fpu_exception : yes > cpuid level : 1 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca > cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow up > bogomips : 4173.80 > clflush size : 32 > cache_alignment : 32 > address sizes : 34 bits physical, 32 bits virtual > power management: ts > > My other machines with Intel processors (Core2Duo, Core-i7) implementing SSE2 > instructions are immune. However, you can tell the GCC compiler to not use the > SSE2 instructions with this flag: -mno-sse2 > > $ cmake ... -DCMAKE_C_FLAGS=-mno-sse2 ... > > The above configuration allows some FPU exceptions to be reported on runtime, > even in a modern CPU. I would like to know if somebody is able to reproduce my > test results and help fixing them. > > Regards, > Pedro > > _______________________________________________ > fluid-dev mailing > listfluid-dev@nongnu.orghttps://lists.nongnu.org/mailman/listinfo/fluid-dev > > > -- > > Sincerely, > Aere > > > _______________________________________________ > fluid-dev mailing list > fluid-dev@nongnu.org > https://lists.nongnu.org/mailman/listinfo/fluid-dev > >
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