[Stk] problems implementing polyphony...

[Gary Scavone]

Hi Morgan,

Thanks for providing some feedback.  But I'm afraid I cannot accept that a very simple FM algorithm is too complex for an iPad.  Clearly, iOS is getting stuck somewhere it shouldn't.  These classes used to run easily in realtime on 1990s-era processors.  There should not be any computation issues.

Regards,

--gary

On 2012-09-17, at 5:41 PM, Morgan Packard <morgan at morganpackard.com> wrote:

> Hi Folks,
> 
> I downloaded the project in question and tried it on my iPad. Indeed, it doesn't run very well at all. I modified the callback so it was filling only 1/10 of every buffer (just so I could get the thing running and try to profile it). Attached is a screen shot of a profile I made with instruments. Most of the time is being spent in Hevy:Metl::tick and FileLoop::tick. I'd think that if there was a bottleneck in one of the stl classes, it would show up here.
> 
> I've experienced MUCH better performance on iOS by using generator::tick(StkFrames &frames), rather than  generator::tick(), and am slowly moving all of my code to use the buffer-at-a-time, rather than sample-at-a-time approach. Hevy:Metl::tick  looks fairly computationally intense to me on its own, and it's chock full of calls to member objects' tick methods. Looks to me like it's simply too expensive, especially with sample-at-a-time calculation.
> 
> -m-
> 
> On Mon, Sep 17, 2012 at 9:56 AM, Gary Scavone <gary at ccrma.stanford.edu> wrote:
> Hi Patrick,
> 
> I think we need to find a profiler that can tell us where the bottleneck is with the FM classes.  The tricky issue might be that the problem doesn't show up using the simulator (according to Rumi), so we might then then have to revert to a trial-and-error approach.  The first think to try would be replacing the vectors of pointers with a simple array of pointers (in FM.h).
> 
> Regards,
> 
> --gary
> 
> On 2012-09-17, at 12:35 AM, "Patrick J. Collins" <patrick at collinatorstudios.com> wrote:
> 
> >> Try Voicer with a simple synth like Simple or Plucked and I think you'll see that it works
> >> great.
> >
> > Wow, you are right..  Polyphony works fine in my game as soon as I
> > switched to Simple and Plucked...
> >
> > That is a huge shame because I really, really, really wanted to feature
> > FM synthesis as the "sound" for my app.
> >
> >> Interesting.  HevyMetl is an FM class, which should not burden the CPU
> >> in any way.  There must be something happening in the FM class that
> >> doesn't work well in iOS … perhaps the use of the c++ vector class to
> >> hold the ADSR and FileLoop pointers?
> >
> > Gary, since you don't have an iPad, is there any chance you'd be up for
> > doing some pairing on my system sometime via screen sharing software
> > like TeamViewer to try to get to the bottom of this?
> >
> > Thanks.
> >
> > Patrick J. Collins
> > http://collinatorstudios.com
> 
> 
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> 
> -- 
> ===============
> Morgan Packard
> cell: (720) 891-0122
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> 
> <Screen Shot 2012-09-17 at 5.20.09 PM.png><Screen Shot 2012-09-17 at 5.33.05 PM.png>