OSStatus callback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) {
	AudioBufferList list;

	// redundant
	list.mNumberBuffers = 1;
	list.mBuffers[0].mData = sampleBuffer;
	list.mBuffers[0].mDataByteSize = 2 * inNumberFrames;
	list.mBuffers[0].mNumberChannels = 1;
	
	ioData = &list;
	
	AudioUnitRender(instance, ioActionFlags, inTimeStamp, 1, inNumberFrames, ioData);

	// the sample buffer now contains samples you can work with

	return 0;
}

void init() {	
	AudioComponentDescription desc;
	
	desc.componentType = kAudioUnitType_Output;
	desc.componentSubType = kAudioUnitSubType_RemoteIO;
	desc.componentFlags = 0;
	desc.componentFlagsMask = 0;
	desc.componentManufacturer = 0;
	
	AudioComponent component = AudioComponentFindNext(NULL, &desc);
		
	AudioComponentInstanceNew(component, &instance);
	
	UInt32 enableIO;
		
	sampleBuffer = malloc(4 * 1024);
	
	enableIO = 1;
	AudioUnitSetProperty(instance,
						 kAudioOutputUnitProperty_EnableIO,
						 kAudioUnitScope_Input,
						 1, // input element
						 &enableIO,
						 sizeof(enableIO));
	
	enableIO = 0;
	AudioUnitSetProperty(instance,
						 kAudioOutputUnitProperty_EnableIO,
						 kAudioUnitScope_Output,
						 0,   //output element
						 &enableIO,
						 sizeof(enableIO));
	
	UInt32 shouldAllocateBuffer = 1;
	AudioUnitSetProperty(instance, kAudioUnitProperty_ShouldAllocateBuffer, kAudioUnitScope_Global, 1, &shouldAllocateBuffer, sizeof(shouldAllocateBuffer));
		
	AudioStreamBasicDescription format;

	format.mBitsPerChannel = 16;
	format.mBytesPerFrame = 2;
	format.mBytesPerPacket = 2;
	format.mChannelsPerFrame = 1;
	format.mFormatFlags = kAudioFormatFlagIsPacked | kAudioFormatFlagIsSignedInteger; //kAudioFormatFlagsCanonical + (kAudioUnitSampleFractionBits << kLinearPCMFormatFlagsSampleFractionShift);
	format.mFormatID = kAudioFormatLinearPCM;
	format.mFramesPerPacket = 1;
	format.mReserved = 0;
	format.mSampleRate = 8000.0;
	
	//set format to output scope
    err = AudioUnitSetProperty(instance, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &format, sizeof(AudioStreamBasicDescription));

	AURenderCallbackStruct callback_struct;
	
	callback_struct.inputProc = callback;
	callback_struct.inputProcRefCon = instance;
	
	err = AudioUnitSetProperty(instance, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 0, &callback_struct, sizeof(callback_struct));

	err = AudioUnitInitialize(instance);
	
	err = AudioOutputUnitStart(instance);
}