Фоновый конфликт аудиоустройства

У меня есть приложение для анализа звука, использующее Audio Units, которое отлично работает, когда приложение запускается изолированно. Однако, если в фоновом режиме работают другие аудиоприложения, AudioUnitRender возвращает ошибку -50.

Кто-нибудь знает способ решить эту проблему, чтобы AudioUnitRender работал даже при запуске других аудиоприложений?

Заранее спасибо.

Инициация аудиосессии

AVAudioSession *session = [AVAudioSession sharedInstance];
[session setPreferredHardwareSampleRate:sampleRate error:&err];
[session setCategory:AVAudioSessionCategoryRecord error:&err];
[session setActive:YES error:&err];
[session setMode:setMode:AVAudioSessionModeMeasurement error:&err];
[session setDelegate:listener];
UInt32 audioRouteOverride = kAudioSessionOverrideAudioRoute_None;
AudioSessionSetProperty (kAudioSessionProperty_OverrideAudioRoute,sizeof (audioRouteOverride),&audioRouteOverride);

Описание блока ввода/вывода:

    OSStatus err;
AudioComponentDescription ioUnitDescription;
ioUnitDescription.componentType = kAudioUnitType_Output;
ioUnitDescription.componentSubType = kAudioUnitSubType_RemoteIO;
ioUnitDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
ioUnitDescrition.componentFlags = 0;
ioUnitDescription.componentFlagsMask = 0;

// Declare and instantiate an audio processing graph
NewAUGraph(&processingGraph);

// Add an audio unit node to the graph, then instantiate the audio unit.
/* 
 An AUNode is an opaque type that represents an audio unit in the context
 of an audio processing graph. You receive a reference to the new audio unit
 instance, in the ioUnit parameter, on output of the AUGraphNodeInfo 
 function call.
 */
AUNode ioNode;
AUGraphAddNode(processingGraph, &ioUnitDescription, &ioNode);

AUGraphOpen(processingGraph); // indirectly performs audio unit instantiation

// Obtain a reference to the newly-instantiated I/O unit. Each Audio Unit
// requires its own configuration.
AUGraphNodeInfo(processingGraph, ioNode, NULL, &ioUnit);

// Initialize below.
AURenderCallbackStruct callbackStruct = {0};
UInt32 enableInput;
UInt32 enableOutput;

// Enable input and disable output.
enableInput = 1; enableOutput = 0;
callbackStruct.inputProc = RenderFFTCallback;
callbackStruct.inputProcRefCon = (__bridge void*)self;

err = AudioUnitSetProperty(ioUnit, kAudioOutputUnitProperty_EnableIO, 
                           kAudioUnitScope_Input, 
                           kInputBus, &enableInput, sizeof(enableInput));

err = AudioUnitSetProperty(ioUnit, kAudioOutputUnitProperty_EnableIO, 
                           kAudioUnitScope_Output, 
                           kOutputBus, &enableOutput, sizeof(enableOutput));

err = AudioUnitSetProperty(ioUnit, kAudioOutputUnitProperty_SetInputCallback, 
                           kAudioUnitScope_Input, 
                           kOutputBus, &callbackStruct, sizeof(callbackStruct));


// Set the stream format.
size_t bytesPerSample = [self ASBDForSoundMode];

err = AudioUnitSetProperty(ioUnit, kAudioUnitProperty_StreamFormat, 
                           kAudioUnitScope_Output, 
                           kInputBus, &streamFormat, sizeof(streamFormat));

err = AudioUnitSetProperty(ioUnit, kAudioUnitProperty_StreamFormat, 
                           kAudioUnitScope_Input, 
                           kOutputBus, &streamFormat, sizeof(streamFormat));



// Disable system buffer allocation. We'll do it ourselves.
UInt32 flag = 1;
err = AudioUnitSetProperty(ioUnit, kAudioUnitProperty_ShouldAllocateBuffer,
                           kAudioUnitScope_Output, 
                           kInputBus, &flag, sizeof(flag));}

Рендеринг обратного вызова:

RIOInterface* THIS = (__bridge_transfer RIOInterface *)inRefCon;
COMPLEX_SPLIT A = THIS->A;
void *dataBuffer = THIS->dataBuffer;
float *outputBuffer = THIS->outputBuffer;
FFTSetup fftSetup = THIS->fftSetup;
float *hammingWeights = THIS->hammingWeights;

uint32_t log2n = THIS->log2n;
uint32_t n = THIS->n;
uint32_t nOver2 = THIS->nOver2;
uint32_t stride = 1;
int bufferCapacity = THIS->bufferCapacity;
SInt16 index = THIS->index;

AudioUnit rioUnit = THIS->ioUnit;
OSStatus renderErr;
UInt32 bus1 = 1;


renderErr = AudioUnitRender(rioUnit, ioActionFlags, 
                            inTimeStamp, bus1, inNumberFrames, THIS->bufferList); 

if (renderErr < 0) {
    return renderErr;
}