iOS AUGraph connecting kAudioUnitSubType_Reverb2 unit between Mixer and kAudioUnitSubType_RemoteIO

In my AuGraph I have following situation:

sampler --------->

                mixer ----> remoteIO

6 callbacks ----->

AudioUnitGraph 0x311E02A:   
Member Nodes:   
   node 1: 'auou' 'rioc' 'appl', instance 0xc66c020 O       
   node 2: 'aumx' 'mcmx' 'appl', instance 0x598f20 O    
   node 3: 'aumu' 'samp' 'appl', instance 0x59ba40 O    
Connections:    node   3 bus   0 => node   2 bus   7  [ 2 ch,  44100 Hz, 'lpcm' (0x00000C2C) 8.24-bit little-endian signed integer, deinterleaved]  
                node   2 bus   0 => node   1 bus   0  [ 2 ch,      0 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]   
Input Callbacks:    {0x1a7bb1, 0xd1f5648} => node   2 bus   0  [1 ch, 44100 Hz]
                    {0x1a7bb1, 0xd1f5648} => node   2 bus   1  [1 ch, 44100 Hz]     {0x1a7bb1, 0xd1f5648} => node   2 bus   2  [1 ch, 44100 Hz]     
                    {0x1a7bb1, 0xd1f5648} => node   2 bus   3  [1 ch, 44100 Hz]     
                    {0x1a7bb1, 0xd1f5648} => node   2 bus   4  [1 ch, 44100 Hz]     
                    {0x1a7bb1, 0xd1f5648} => node   2 bus   5  [1 ch, 44100 Hz]           
                    {0x1a7bb1, 0xd1f5648} => node   2 bus   6  [1 ch, 44100 Hz]

And everything is working fine, nevertheless formats don't match. Callbacks work and sampler sounds like a charm.

Now I try to plug in reverb like this:

sampl->

mixer ----> reverb --> remoteIO

6 call-->

And I get this graph:

AudioUnitGraph 0x313402A:
  Member Nodes:
    node 1: 'auou' 'rioc' 'appl', instance 0x569060 O  
    node 2: 'aumx' 'mcmx' 'appl', instance 0x56a210 O  
    node 3: 'aumu' 'samp' 'appl', instance 0x56b200 O  
    node 4: 'aufx' 'rvb2' 'appl', instance 0x56ba30 O  
  Connections:
    node   3 bus   0 => node   2 bus   7  [ 2 ch,  44100 Hz, 'lpcm' (0x00000C2C) 8.24-bit little-endian signed integer, deinterleaved]
    node   2 bus   0 => node   4 bus   0  [ 2 ch,  44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]
    node   4 bus   0 => node   1 bus   0  [ 2 ch,      0 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]

    Input Callbacks: (the same as before)

And the error: AUGraphInitialize error: -10868*

Connection code:

result = AUGraphConnectNodeInput ( processingGraph,
            mixerNode,         // source node
             0,                 // source node output bus number
             revNode,            // destination node
             0                  // desintation node input bus number
         );


result = AUGraphConnectNodeInput ( processingGraph,
                                                                    revNode,         // source node
                                                                    0,                 // source node output bus number
                                                                    iONode,            // destination node
                                                                    0                  // desintation node input bus number                                                         );

Also I tried to unify formats for Reverb and Mixer:

AudioStreamBasicDescription asbd;
UInt32 asbdSize = sizeof (asbd);
memset (&asbd, 0, sizeof (asbd));

AudioUnitGetProperty(mixerUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &asbd, &asbdSize);
AudioUnitSetProperty(reverbUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &asbd, sizeof(asbd));

What am I doing wrong? Sorry for the bad formatting, joined today.

I had the same problem, but found out that I had to copy the ASBD from one of the units at the mixer input and set it to the output scope of the mixer unit.

AudioStreamBasicDescription asbd;
UInt32 sz = sizeof(asbd);
result = AudioUnitGetProperty(someUnitBeforeMixer, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &asbd, &sz);
NSCAssert (result == noErr, @"Unable to get ASBD. Error code: %d '%.4s'", (int) result, (const char *)&result);
result = AudioUnitSetProperty(mixerUnit,
                              kAudioUnitProperty_StreamFormat,
                              kAudioUnitScope_Output,
                              0,
                              &asbd,
                              sizeof(asbd));
NSCAssert (result == noErr, @"Unable to set ASBD. Error code: %d '%.4s'", (int) result, (const char *)&result);

Instead of copying the ASBD, you could set it up manually if you know what format it should be.