Multiple buses routed to different group mixer makes them to share variables in a Render Callback

Question

I had a render callback with 20 buses synchronized and routed to a same mixer but now I need to apply effects to some of these 20 buses, so now, they are divided into groups of 5.

So now, I have 20 buses divided into 4 groups.

Buses 0-4 -routed to - Mixer1

AUGraphSetNodeInputCallback (processingGraph,mixer1Node,
                                                  input, //0-4
                                                  &inputCallbackStruct
                                                  );

Buses 5-9 -routed to - Mixer2

AUGraphSetNodeInputCallback (processingGraph,mixer2Node,
                                                  input, //0-4
                                                  &inputCallbackStruct
                                                  );

Buses 10-14 -routed to - Mixer3 ...

Buses 15-19 -routed to - Mixer4 ...

Now, my issue is every of these groups are getting [0] to [4] inBusNumber, with the same data in the render callback. So the old inBusNumber [5] now is [0] of Mixer2, with the same render data of bus [0] of Mixer1. All the variables are now shared with buses of the other Mixers.

Now my complex render code is useless .... I need independent variables on each bus.

Any ideas how to deal with it ?

Is it a matter of losing track of which bus is which within the render callback? — dave234, Feb 23 '17 at 04:42
I'm moving to kAudioUnitSubType_MatrixMixer , seems better for my purpose — Fischer, Feb 23 '17 at 09:58
How did kAudioUnitSubType_MatrixMixer work out? Post your solution! — dave234, Feb 28 '17 at 21:54

score 0 · Accepted Answer · answered Mar 01 '17 at 11:37

I made it with kAudioUnitSubType_MatrixMixer. It allows to have any number of inputs and any number of outputs. So I'm setting buses 0-4 to output 0, buses 0-9 to output 1... etc. It's possible to set volume from any input to any output of the Matrix Mixer in this way:

 UInt32 element = (inputChannel<<16) | outputChannel;
 AudioUnitSetParameter(mixerMatrix, kMatrixMixerParam_Volume, kAudioUnitScope_Global, element, gain, 0);

With this method, all the buses are routed to the same mixer (MatrixMixer) and I can share variables in the render callback.

Multiple buses routed to different group mixer makes them to share variables in a Render Callback

1 Answers1