xcode - AUiPodEQ AUGraph

Question

I'm developing a music application for iOS using the AVAudioplayer, in which I want to implement an equalizer. I searched the internet for a good solution, and ended up with and AUGraph configuration like this:

// multichannel mixer unit
AudioComponentDescription mixer_desc;
mixer_desc.componentType = kAudioUnitType_Mixer;
mixer_desc.componentSubType = kAudioUnitSubType_MultiChannelMixer;
mixer_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
mixer_desc.componentFlags = 0;
mixer_desc.componentFlagsMask = 0;
// iPodEQ unit
AudioComponentDescription eq_desc;
eq_desc.componentType = kAudioUnitType_Effect;
eq_desc.componentSubType = kAudioUnitSubType_AUiPodEQ;
eq_desc.componentManufacturer =  kAudioUnitManufacturer_Apple;
eq_desc.componentFlags = 0;
eq_desc.componentFlagsMask = 0;
// output unit
AudioComponentDescription output_desc;
output_desc.componentType = kAudioUnitType_Output;
output_desc.componentSubType = kAudioUnitSubType_GenericOutput;
output_desc.componentManufacturer =  kAudioUnitManufacturer_Apple;
output_desc.componentFlags = 0;
output_desc.componentFlagsMask =  0;

// create a new AUGraph
OSStatus result = NewAUGraph(&mGraph);
// Add Audio Nodes to graph
AUNode outputNode;
AUNode eqNode;
AUNode mixerNode;
AUGraphAddNode(mGraph, &mixer_desc, &mixerNode);
AUGraphAddNode(mGraph, &eq_desc, &eqNode);

AUGraphAddNode(mGraph, &output_desc, &outputNode);

// open the graph AudioUnits (but not initialized)
result = AUGraphOpen(mGraph);
// grab the audio unit instances from the nodes
AudioUnit mEQ;
AudioUnit mMixer;
result = AUGraphNodeInfo(mGraph, mixerNode, NULL, &mMixer);
result = AUGraphNodeInfo(mGraph, eqNode, NULL, &mEQ);

// set number of input buses for the mixer Audio Unit
UInt32 numbuses = 0;
AudioUnitSetProperty ( mMixer, kAudioUnitProperty_ElementCount,
                      kAudioUnitScope_Input, 0, &numbuses, sizeof(numbuses));

// get the equalizer factory presets list
CFArrayRef mEQPresetsArray;
UInt32 sizeof1 = sizeof(mEQPresetsArray);
AudioUnitGetProperty(mEQ, kAudioUnitProperty_FactoryPresets,
                     kAudioUnitScope_Global, 0, &mEQPresetsArray, &sizeof1);


result = AUGraphConnectNodeInput(mGraph, mixerNode, 0, eqNode, 0);
result = AUGraphConnectNodeInput(mGraph, eqNode, 0, outputNode, 0);

AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Enable, kAudioUnitScope_Input, 0, 1, 0);

AUPreset *aPreset = (AUPreset*)CFArrayGetValueAtIndex(mEQPresetsArray, 7);
AudioUnitSetProperty (mEQ, kAudioUnitProperty_PresentPreset,
                      kAudioUnitScope_Global, 0, aPreset, sizeof(AUPreset));

AUGraphInitialize(mGraph);
AUGraphStart(mGraph);

The AUGraph is running, but the EQ isn't applied. The argument '7' in AUPreset *aPreset = (AUPreset*)CFArrayGetValueAtIndex(mEQPresetsArray, 7); is the index of the equalizer that should be applied. (Electronic) I got that index from logging the values of the mEQPresetsArray-Array:

for (int i = 0; i < CFArrayGetCount(mEQPresetsArray); i++) {
    AUPreset *aPreset = (AUPreset*)CFArrayGetValueAtIndex(mEQPresetsArray, i);
    NSLog(@"%d: %@", (int)aPreset->presetNumber, aPreset->presetName);
}

How can I solve my problem? I've already tried the NVDSP, but it didn't seem to be working as well. I didn't find any other solution on the internet.

Thanks in advance, Fabian.

Answer 1

If this is for iOS then you need to use kAudioUnitSubType_RemoteIO instead of kAudioUnitSubType_GenericOutput.