I have been able to reproduce the very odd behavior of instruments played from 
this bank.  I’ll report back when I have more information to share.

-DS


> On Jul 6, 2018, at 10:53 AM, Bartosz Nowotny <[email protected]> wrote:
> 
> A quick followup:
> 
> Is it possible that some of the instruments are running out of voices (e.g. 
> the aforementioned piano instrument)? As an experiment I switched synth units 
> from AUMIDISynth to AUSampler and tried setting voice count. It seems the 
> default is 64 voices and I tried to set it to 128 or even 256 but 
> unfortunately that seemed to have no effect on the issue. I accomplished that 
> by getting the ClassInfo property with global scope, casting to a dictionary, 
> assigning an NSNumber to "voice count" key and finally setting the ClassInfo 
> back. Is that the correct way to do this? There were no errors logged. 
> 
> Bartosz
> 
> On Thu, Jul 5, 2018 at 12:19 PM, Bartosz Nowotny <[email protected] 
> <mailto:[email protected]>> wrote:
> I'm using AVAudioSession to configure my audio session and set up preferred 
> sample rate, buffer size. Other than that, I'm using exclusively the C API - 
> AUGraph and AudioUnits.
> 
> My app *sometimes* needs more than 1 MIDISynth unit running at a time because 
> some songs require 2 different soundfonts to be loaded simultaneously. As far 
> as my understanding goes, a MIDISynth unit can only load a single soundfont. 
> Am I fundamentally mistaken here?
> 
> Since my original email, I configured my audio session and all the audio 
> units to use consistent sample rate so that no resampling has to be done at 
> any point. The issue still pertains.
> 
> The issue is clearly audible when using Yamaha 9ft Grand piano preset from 
> CompiFONT (http://pphidden.wixsite.com/compifont 
> <http://pphidden.wixsite.com/compifont>). This particular soundfont is really 
> big in size. Since I only need the piano preset, I use a soundfont that has 
> just that one preset extracted (download: 
> https://mega.nz/#!nYoz0YxZ!gvwd7hCibvG0_n8xEunSJlBapo9d6VhvLg7uNQFsSrw 
> <https://mega.nz/#!nYoz0YxZ!gvwd7hCibvG0_n8xEunSJlBapo9d6VhvLg7uNQFsSrw>). 
> 
> I should also say that this issue is present regardless of the number of 
> MIDISynth units running - it sounds the same with 1 MIDISynth unit or more.
> Moreover, that very same soundfont and bank/preset is used in Android version 
> of the app where the backing synth is FluidSynth and it sounds lovely - with 
> polyphony count set to 64!
> 
> If it would be helpful, I can record how the piano sounds in my iOS app vs a 
> synth on Windows or Android.
> 
> Regards,
> Bartosz
> 
> On Thu, Jul 5, 2018 at 4:01 AM, [email protected] 
> <mailto:[email protected]> <[email protected] 
> <mailto:[email protected]>> wrote:
> Are you using the C API or the Objective C API?
> 
> Why do you have multiple 16-channel MIDISynth units running?  You could 
> possibly run out of CPU because they cannot steal voices from each other.
> 
> If your MIDISynth code works for one bank but not another, I find it hard to 
> imagine it is a configuration issue.
> 
> Can you point me to the banks in question?
> 
> -DS
> 
> > On Jul 3, 2018, at 3:02 PM, Bartosz Nowotny <[email protected] 
> > <mailto:[email protected]>> wrote:
> > 
> > Hello
> > 
> > I need advice on how to properly configure AudioUnits in my MIDISynth iOS 
> > app.
> > 
> > In my code I start by configuring AudioSession: I set the right category 
> > (playback), preferred sample rate and buffer size and then start the 
> > session.
> > Next up, I create the graph: multiple synth units  
> > (kAudioUnitSubType_MIDISynth) -> multichannel mixer -> remote IO.
> > For mixer unit, I configure number of input elements (buses) and maximum 
> > frames per slice.
> > For synth units, I configure the soundbank URL and maximum frames per slice.
> > 
> > This set up is enough for my app to successfully produce music by sending 
> > MIDI note on/off events to specific synth units. For some soundfonts, the 
> > produced sound is not correct, as if it was distorted. Because the 
> > soundfonts I'm using are popular and publicly available soundfonts, tested 
> > on multiple devices and different synths, I'm pretty certain the soundfonts 
> > are not at fault here. My best guess is that I'm missing parts of the 
> > configuration:
> > 
> > 1. Is any additional configuration required for any of the AudioUnits I 
> > use? In particular, should I configure synth units output stream format, so 
> > that for instance, the sample rate matches what is actually used by the 
> > hardware? Should I also configure stream format for the mixer or IO units? 
> > How should the stream format configs look like?
> > 2. If I do need to do the above configuration, how should I respond to 
> > audio session route changes? I noticed, for instance, that plugging in 
> > headphones changes the hardware output sample rate from 48kHz to 44.1kHz.
> > 
> > Regards,
> > Bartosz
> > 
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> 
> 

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