Setting up effect audio units for CoreAudio - objective-c

Question

I'm trying to setup a high-pass filter but AUGraphStart gives me -10863 when I try. I cannot find much documntation at all. Here is my attent to set up the filter:
- (void)initializeAUGraph{
AUNode outputNode;
AUNode mixerNode;
AUNode effectNode;
NewAUGraph(&mGraph);
// Create AudioComponentDescriptions for the AUs we want in the graph
// mixer component
AudioComponentDescription mixer_desc;
mixer_desc.componentType = kAudioUnitType_Mixer;
mixer_desc.componentSubType = kAudioUnitSubType_AU3DMixerEmbedded;
mixer_desc.componentFlags = 0;
mixer_desc.componentFlagsMask = 0;
mixer_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// output component
AudioComponentDescription output_desc;
output_desc.componentType = kAudioUnitType_Output;
output_desc.componentSubType = kAudioUnitSubType_RemoteIO;
output_desc.componentFlags = 0;
output_desc.componentFlagsMask = 0;
output_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
//effect component
AudioComponentDescription effect_desc;
effect_desc.componentType = kAudioUnitType_Effect;
effect_desc.componentSubType = kAudioUnitSubType_HighPassFilter;
effect_desc.componentFlags = 0;
effect_desc.componentFlagsMask = 0;
effect_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// Add nodes to the graph to hold our AudioUnits
AUGraphAddNode(mGraph, &output_desc, &outputNode);
AUGraphAddNode(mGraph, &mixer_desc, &mixerNode);
AUGraphAddNode(mGraph, &effect_desc, &effectNode);
// Connect the nodes
AUGraphConnectNodeInput(mGraph, mixerNode, 0, effectNode, 0);
AUGraphConnectNodeInput(mGraph, effectNode, 0, outputNode, 0);
//Open Graph
AUGraphOpen(mGraph);
// Get a link to the mixer AU
AUGraphNodeInfo(mGraph, mixerNode, NULL, &mMixer);
// Get a link to the effect AU
AUGraphNodeInfo(mGraph, effectNode, NULL, &mEffect);
//Setup buses
size_t numbuses = track_count;
UInt32 size = sizeof(numbuses);
AudioUnitSetProperty(mMixer, kAudioUnitProperty_ElementCount, kAudioUnitScope_Input, 0, &numbuses, size);
//Setup Stream Format Data
AudioStreamBasicDescription desc;
size = sizeof(desc);
// Setup Stream Format
desc.mSampleRate = kGraphSampleRate;
desc.mFormatID = kAudioFormatLinearPCM;
desc.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
desc.mBitsPerChannel = sizeof(AudioSampleType) * 8; // AudioSampleType == 16 bit signed ints
desc.mChannelsPerFrame = 1;
desc.mFramesPerPacket = 1;
desc.mBytesPerFrame = sizeof(AudioSampleType);
desc.mBytesPerPacket = desc.mBytesPerFrame;
// Loop through and setup a callback for each source you want to send to the mixer.
for (int i = 0; i < numbuses; ++i) {
// Setup render callback struct
AURenderCallbackStruct renderCallbackStruct;
renderCallbackStruct.inputProc = &renderInput;
renderCallbackStruct.inputProcRefCon = self;
// Connect the callback to the mixer input channel
AUGraphSetNodeInputCallback(mGraph, mixerNode, i, &renderCallbackStruct);
// Apply Stream Data
AudioUnitSetProperty(mMixer, kAudioUnitProperty_StreamFormat,kAudioUnitScope_Input,i,&desc,size);
AudioUnitSetParameter(mMixer, k3DMixerParam_Distance, kAudioUnitScope_Input, i, rand() % 6, 0);
rotation[i] = rand() % 360;
rotation_speed[i] = rand() % 5;
AudioUnitSetParameter(mMixer, k3DMixerParam_Azimuth, kAudioUnitScope_Input, i, rotation[i], 0);
AudioUnitSetParameter(mMixer, k3DMixerParam_Elevation, kAudioUnitScope_Input, i, 30, 0);
}
// Reset stream fromat data to 0
memset (&desc, 0, sizeof (desc));
// Setup output stream format
desc.mSampleRate = kGraphSampleRate;
// Apply Stream Data to Output
AudioUnitSetProperty(mEffect,kAudioUnitProperty_StreamFormat,kAudioUnitScope_Input,0,&desc,size);
AudioUnitSetProperty(mEffect,kAudioUnitProperty_StreamFormat,kAudioUnitScope_Output,0,&desc,size);
AudioUnitSetProperty(mMixer,kAudioUnitProperty_StreamFormat,kAudioUnitScope_Output,0,&desc,size);
//All done so initialise
AUGraphInitialize(mGraph);
}
It works when I remove the high pass filter. How do I get the filter working?
Thank you.
PS: Is the 3D elevation supposed to do nothing?

Answer 1

if u still have the problem...u should add a converter unit between the mixernode and the effect node and set the input format of it as the mixer output and the output format to the format u get from audiounitgetproperty (converternode)

Answer 2

Not all Audio Units that are available on OSX are available on iOS. In fact, only a few are. According to below documentation the highpassfilter effect is not supported on iOS : http://developer.apple.com/library/ios/#documentation/MusicAudio/Conceptual/AudioUnitHostingGuide_iOS/UsingSpecificAudioUnits/UsingSpecificAudioUnits.html#//apple_ref/doc/uid/TP40009492-CH17-SW1
"The iPod EQ unit (subtype kAudioUnitSubType_AUiPodEQ) is the only effect unit provided in iOS 4."
Note that it mentions iOS4. But I am unable to find any documentation on this for later versions of iOS.