IOS: RemoteIO audio device not working on iPhone

Question

I am trying to create my own Sound Unit Audio effects based on microphone input. This application allows the simultaneous input / output of a microphone to the speaker. I can apply effects and work using the simulator, but when I try to check on the iPhone, I don’t hear anything. I am inserting 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 microphone audio data is available. But never come here when I test 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 just needed to initialize the AudioSession before playing / recording. I did this 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); 

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