Re: [fluid-dev] problems with fluidsynth 1.1.6 on a raspberry pi

[Jan Newmarch]

Hi

Sorry, maybe I didn't mention it. I tried both linear and no
interpolation ("interp 1" and "interp 0"). It didn't make any difference
that I could hear or see in CPU usage.

Jan
--

On Fri, 2012-11-23 at 21:51 -0600, S. Christian Collins wrote:
> Sorry to keep repeating this, but have you tried switching FluidSynth to
> linear interpolation yet? It seems a lot of your CPU usage is tied up in
> the 4-point interpolation that FluidSynth defaults to.
> -~Chris
> 
> On 11/23/2012 07:27 PM, Jan Newmarch wrote:
> > On Wed, 2012-11-21 at 16:26 +0100, David Henningsson wrote:
> >
> >> That is a very valid point; we might not strive to eliminate the average 
> >> CPU as much as the worst-case CPU, even if both are important.
> >>
> >> Maybe you could run "perf top -d 1" and monitor that, to see if anything 
> >> special happens while the CPU maxes out?
> > No luck :-(. The output looked the same for good and bad bits
> >
> >> I have another idea too; maybe we're trashing the L1 cache? If so, 
> >> running with -z 1024 or -z 512 might give better result (combined with 
> >> using floats instead of doubles). Here, -z 1024 gave better results, but 
> >> not by much. The Raspberry Pi does not seem to have a L2 Cache (for CPU 
> >> usage), so it might diff more for you.
> > Just setting -z to either 512 or 1024 and floats instead of doubles
> > didn't work by itself.
> >
> >> If we do an extremely rough calculation: We have a computer of 1 GHz, a 
> >> sample rate of 50 kHz, and 100 voices; that gives us only 200 cycles per 
> >> voice and sample. And we still have to do several floating point 
> >> calculations every sample. So this leads me to believe that maybe there 
> >> is no holy grail solution to this problem, nothing obvious we're missing 
> >> that causes this CPU usage. Maybe it's more of trying one thing here and 
> >> another thing there.
> > Sorry to pull in the "competition" here... Timidity gives CPU usage of
> > around 70-90% on nightsin.kar. But it doesn't have the blowouts to above
> > 100%, and plays okay (just). I don't know what the default settings are
> > for Timidity though. Maybe it is just fine tuning, although Aere is
> > getting good results on a slower CPU.
> >
> > On another tangent, running Fluidsynth as a server to the ALSA MIDI
> > sequencer alsa_seq plays okay with rate set to 22050.
> >
> 

-- 
Dr Jan Newmarch
Head of ICT and Commerce (Higher Education)

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