The thing that has most effect on low end processor is to halve the sample rate with the flag '-r22050'.
see http://sourceforge.net/apps/trac/fluidsynth/wiki/ExampleCommandLines also see http://sourceforge.net/apps/trac/fluidsynth/wiki/LowLatency Louis On Tue, Jan 7, 2014 at 5:37 PM, Element Green <jgr...@users.sourceforge.net>wrote: > Hello Marcus, > > I don't have experience with FluidSynth on ARM, so this is more general in > scope. > > The ARM platform needs to have some sort of FPU in order to achieve any > sort of realtime output (I know a lot of them do nowadays, so probably not > an issue). As to latency, there are a lot of variables. FluidSynth itself > can achieve very low latency (I think it would be the buffer fill size, > which I believe is 64 samples by default - 64 samples a 48KHz is about > 1.3ms). It really comes down to the rest of the system. FluidSynth will > need to enable realtime SCHED_FIFO scheduling. The Linux kernel will play > a huge role in achieving low latency without underruns. For very low > latency, the Linux kernel will likely need to be built to be fully > preemptive and may need to be patched (although I believe a lot of > preemption related stuff has made it back into the stock kernel source). > According to one information source, the preemption related code is > platform independent and should work just as well on ARM as X86 ( > http://lwn.net/images/conf/rtlws11/papers/proc/p11.pdf). The audio > interface and drivers will most likely end up determining the lowest > underrun free latency possible on a given architecture, provided there > aren't other drivers which cause latency spikes. > > I run the Ubuntu lowlatency Kernel on my laptop, which appears to not have > PREEMPT-RT enabled and I can achieve 20ms without much issue (or somewhere > there abouts, don't quote me on that ;-) Lower than that and I start to > get occasional underruns, increasing the lower I go. This is with a USB > Edirol 24 bit interface. I also have to turn off my Ethernet device, due > to some driver or IRQ priority issue, which causes latency spikes at > periodic intervals (like every 2 minutes or something). > > Hope that helps. > Best regards, > > Element > > > > On Tue, Jan 7, 2014 at 7:21 AM, Marcus Weseloh <mar...@weseloh.cc> wrote: > >> Hi, >> >> I am looking for a low-powered platform to run fluidsynth with >> real-time midi input (with a fairly small soundfont < 50mb, not a huge >> 500mb monster), aiming for for very low latency performance. I've seen >> a few posts and articles about fluidsynth on a Raspberry PI, but they >> usually talk about "some latency issues". Has anybody got experience >> with one of the more powerful ARM devel boards like the beaglebone >> black, cubieboard or similar? >> >> I would love to hear your thoughts and ideas, especially with regard >> to real-time performance. >> >> Cheers, >> >> Marcus >> >> _______________________________________________ >> fluid-dev mailing list >> fluid-dev@nongnu.org >> https://lists.nongnu.org/mailman/listinfo/fluid-dev >> > > > _______________________________________________ > fluid-dev mailing list > fluid-dev@nongnu.org > https://lists.nongnu.org/mailman/listinfo/fluid-dev > >
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