No problem.

If I don't call the set element count API, I do get an error when trying to 
connect to the input, so that's not the issue here. However, I can't hear 
anything from any input greater than 7.


Anyone else may have a clue?


Thanks!



________________________________
From: Dave O'Neill <[email protected]>
Sent: Monday, March 7, 2016 4:14 PM
To: Marcelo Birnbach; [email protected]
Subject: Re: kAudioUnitType_Mixer limit?

I don't have it handy,  but the thing I was testing to see if I could change 
the kAudioUnitProperty_ElementCount after it was initialized, I was able to 
update the property while audio was being produced.  Maybe try initializing 
first.  Also, I wasn't using an AUGraph, not sure if that changes anything.

Dave

On Mon, Mar 7, 2016 at 1:03 PM, Marcelo Birnbach 
<[email protected]<mailto:[email protected]>> wrote:

Hi Dave,


Thanks for your response. We call that API before connecting anything to the 
mixer:


    err = AudioUnitSetProperty(mMixer, kAudioUnitProperty_ElementCount, 
kAudioUnitScope_Input, 0, &numbuses, sizeof(numbuses));

    if (err) {

        NSLog(@"Error - initializeAUGraph - AudioUnitSetProperty - 
kAudioUnitProperty_ElementCount - error:%d", err);

        return false;

    }



We are compiling with target SDK 10.6 (I'm not sure that makes any difference 
but we need backward compatibility).


It's interesting you mentioned you've used it with 100 for a test and that 
worked. Do you happen to have that test handy so I can give it a try?


Thanks

Marcelo



________________________________
From: Dave O'Neill <[email protected]<mailto:[email protected]>>
Sent: Monday, March 7, 2016 3:43 PM
To: Marcelo Birnbach
Cc: [email protected]<mailto:[email protected]>
Subject: Re: kAudioUnitType_Mixer limit?

For kAudioUnitSubType_MultiChannelMixer you have to set the channel count 
before using any more than eight.  I've used 100 for a test and it was smooth 
sailing.


UInt32 channelCount = 16;
AudioUnitSetProperty(mixerUnit , kAudioUnitProperty_ElementCount, 
kAudioUnitScope_Input, 0, &channelCount, sizeof(channelCount));



On Mon, Mar 7, 2016 at 12:31 PM, Marcelo Birnbach 
<[email protected]<mailto:[email protected]>> wrote:

Hi all,


I wonder if there's any limit to the number of input buses a 
kAudioUnitType_Mixer can use. I empirically found that buses higher than ~8 are 
discarded. That means that I can mix up to 7 inputs but the 8th and higher are 
silent in the output mix.


I tried with kAudioUnitSubType_MultiChannelMixer, kAudioUnitSubType_StereoMixer 
and kAudioUnitSubType_3DMixer sub-types. All input buses are set to mono 
44100hz and the mixer output is stereo.


I got the same behavior regardless whether I connected other nodes to the mixer 
input buses or using render input callbacks.


We are calling setting setting the kAudioUnitProperty_ElementCount property 
with the right value (e.g. 11 buses).


Does anyone have an idea of what's going on? I was thinking about using N 
number of mixers and connecting them to a master mix but that sounds like a 
hack to me and I'd love to understand what's going on first.


Thanks

Marcelo




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