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]>
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]>
> *Sent:* Monday, March 7, 2016 3:43 PM
> *To:* Marcelo Birnbach
> *Cc:* [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]>
> 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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