iOS: Audio Unit RemoteIO not working on iPhone - iphone

Question

I'm trying to create my own custom sound effects Audio Unit based on the input from the mic. This application allows simultaneous input/output from the microphone to speaker. I can apply effects and work using the simulator, but when I try to test on the iPhone I can't hear anything. I paste my code if anyone can help me:
- (id) init{
self = [super init];
OSStatus status;
// Describe audio component
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// Get component
AudioComponent inputComponent = AudioComponentFindNext(NULL, &desc);
// Get audio units
status = AudioComponentInstanceNew(inputComponent, &audioUnit);
checkStatus(status);
// Enable IO for recording
UInt32 flag = 1;
status = AudioUnitSetProperty(audioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
kInputBus,
&flag,
sizeof(flag));
checkStatus(status);
// Enable IO for playback
status = AudioUnitSetProperty(audioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
kOutputBus,
&flag,
sizeof(flag));
checkStatus(status);
// Describe format
AudioStreamBasicDescription audioFormat;
audioFormat.mSampleRate = 44100.00;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket = 1;
audioFormat.mChannelsPerFrame = 1;
audioFormat.mBitsPerChannel = 16;
audioFormat.mBytesPerPacket = 2;
audioFormat.mBytesPerFrame = 2;
// Apply format
status = AudioUnitSetProperty(audioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
kInputBus,
&audioFormat,
sizeof(audioFormat));
checkStatus(status);
status = AudioUnitSetProperty(audioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&audioFormat,
sizeof(audioFormat));
checkStatus(status);
// Set input callback
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = self;
status = AudioUnitSetProperty(audioUnit,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Global,
kInputBus,
&callbackStruct,
sizeof(callbackStruct));
checkStatus(status);
// Set output callback
callbackStruct.inputProc = playbackCallback;
callbackStruct.inputProcRefCon = self;
status = AudioUnitSetProperty(audioUnit,
kAudioUnitProperty_SetRenderCallback,
kAudioUnitScope_Global,
kOutputBus,
&callbackStruct,
sizeof(callbackStruct));
checkStatus(status);
// Allocate our own buffers (1 channel, 16 bits per sample, thus 16 bits per frame, thus 2 bytes per frame).
// Practice learns the buffers used contain 512 frames, if this changes it will be fixed in processAudio.
tempBuffer.mNumberChannels = 1;
tempBuffer.mDataByteSize = 512 * 2;
tempBuffer.mData = malloc( 512 * 2 );
// Initialise
status = AudioUnitInitialize(audioUnit);
checkStatus(status);
return self;
}
This callback is called when new audio data from the microphone is available. But never enter here when I test on the iPhone:
static OSStatus recordingCallback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) {
AudioBuffer buffer;
buffer.mNumberChannels = 1;
buffer.mDataByteSize = inNumberFrames * 2;
buffer.mData = malloc( inNumberFrames * 2 );
// Put buffer in a AudioBufferList
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0] = buffer;
// Then:
// Obtain recorded samples
OSStatus status;
status = AudioUnitRender([iosAudio audioUnit],
ioActionFlags,
inTimeStamp,
inBusNumber,
inNumberFrames,
&bufferList);
checkStatus(status);
// Now, we have the samples we just read sitting in buffers in bufferList
// Process the new data
[iosAudio processAudio:&bufferList];
// release the malloc'ed data in the buffer we created earlier
free(bufferList.mBuffers[0].mData);
return noErr;
}

Answer 1

I solved my problem. I simply needed to initialize the AudioSession before playing/recording. I did so with the following code:
OSStatus status;
AudioSessionInitialize(NULL, NULL, NULL, self);
UInt32 sessionCategory = kAudioSessionCategory_PlayAndRecord;
status = AudioSessionSetProperty (kAudioSessionProperty_AudioCategory,
sizeof (sessionCategory),
&sessionCategory);
if (status != kAudioSessionNoError)
{
if (status == kAudioServicesUnsupportedPropertyError) {
NSLog(#"AudioSessionInitialize failed: unsupportedPropertyError");
}else if (status == kAudioServicesBadPropertySizeError) {
NSLog(#"AudioSessionInitialize failed: badPropertySizeError");
}else if (status == kAudioServicesBadSpecifierSizeError) {
NSLog(#"AudioSessionInitialize failed: badSpecifierSizeError");
}else if (status == kAudioServicesSystemSoundUnspecifiedError) {
NSLog(#"AudioSessionInitialize failed: systemSoundUnspecifiedError");
}else if (status == kAudioServicesSystemSoundClientTimedOutError) {
NSLog(#"AudioSessionInitialize failed: systemSoundClientTimedOutError");
}else {
NSLog(#"AudioSessionInitialize failed! %ld", status);
}
}
AudioSessionSetActive(TRUE);
...