Remote IO audio is very noisy - ios

Question

I am new to core audio and remote io. I need data of size 320 bytes which I encode and send. Also a minimum of 50 frames per second. Here is what I have done:
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
desc.componentManufacturer = 0;
// Get component
AudioComponent inputComponent = AudioComponentFindNext(NULL, &desc);
// Get audio units
 AudioComponentInstanceNew(inputComponent, &audioUnit);
// Enable IO for recording
UInt32 flag = 1; AudioUnitSetProperty(audioUnit,  kAudioOutputUnitProperty_EnableIO,  kAudioUnitScope_Input,   kInputBus,  &flag,   sizeof(flag));
// Enable IO for playback AudioUnitSetProperty(audioUnit,  kAudioOutputUnitProperty_EnableIO,   kAudioUnitScope_Output,   kOutputBus, &flag,   sizeof(flag));
UInt32 shouldAllocateBuffer = 1;
AudioUnitSetProperty(audioUnit, kAudioUnitProperty_ShouldAllocateBuffer, kAudioUnitScope_Global, 1, &shouldAllocateBuffer, sizeof(shouldAllocateBuffer));
// Describe format
audioFormat.mSampleRate = 8000.00;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger|kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket = 1;
audioFormat.mChannelsPerFrame = 1;
audioFormat.mBitsPerChannel = 16;
audioFormat.mBytesPerPacket = 2;
audioFormat.mBytesPerFrame = 2;
// Apply format AudioUnitSetProperty(audioUnit,  kAudioUnitProperty_StreamFormat,  kAudioUnitScope_Output, 1,   &audioFormat,  sizeof(audioFormat));
AudioUnitSetProperty(audioUnit,  kAudioUnitProperty_StreamFormat,  kAudioUnitScope_Input,  0,  &audioFormat,  sizeof(audioFormat));
// Set input callback
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = self;
AudioUnitSetProperty(audioUnit,   kAudioOutputUnitProperty_SetInputCallback,   kAudioUnitScope_Global,   1,   &callbackStruct,   sizeof(callbackStruct));
// Set output callback
callbackStruct.inputProc = playbackCallback;
callbackStruct.inputProcRefCon = self;
 AudioUnitSetProperty(audioUnit, kAudioUnitProperty_SetRenderCallback,  kAudioUnitScope_Global,   0, &callbackStruct,  sizeof(callbackStruct));
// Initialise
AudioUnitInitialize(audioUnit);
AudioOutputUnitStart(audioUnit);
With this settings, i get 186 frames in the callback method when tried with device.
I have allocated by buffer:
bufferList = (AudioBufferList*) malloc(sizeof(AudioBufferList));
bufferList->mNumberBuffers = 1; //mono input
for(UInt32 i=0;i<bufferList->mNumberBuffers;i++)
{
bufferList->mBuffers[i].mNumberChannels = 1;
bufferList->mBuffers[i].mDataByteSize = 2*186;
bufferList->mBuffers[i].mData = malloc(bufferList->mBuffers[i].mDataByteSize);
} 
From this 372(2 x 186)  bytes in the callback, i took 320 byte data and used as per my requirement. It is working, but very noisy.
Someone please help me. I am in big trouble.

Answer 1

A couple of suggestions -
Sample rate and buffer size get set using the AVAudioSession class.
386 is an unusual number of frames. Your callback is probably asking for 512 or 1024. You might try using a ring buffer to allow varying varying buffer size/ frame rates to suit your needs.
Here are some examples:
MixerHost
TimeCode