Audio Unit file recording with aurioTouch - AudioStreamBasicDescription configuration issue? - ios

Question

I've started down the path on learning Audio Unit with aurioTouch. After a few days of learning Audio Unit, I'm still feeling a bit lost and I think I'm missing something very obvious.
Full source can be view at: http://pastebin.com/LXLYDEhy
Also listed the partial source down here
In my performRender callback, I've changed the code to
static OSStatus performRender (void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
OSStatus err = noErr;
AudioController *audioController = (__bridge AudioController *)inRefCon;
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0].mData = NULL;
OSStatus status;
status = AudioUnitRender(cd.rioUnit,
ioActionFlags,
inTimeStamp,
inBusNumber,
inNumberFrames,
&bufferList); // bufferList.mBuffers[0].mData is null
status = ExtAudioFileWriteAsync(audioController.extAudioFileRef, bufferList.mNumberBuffers, &bufferList);
}
The audio units are setup like this
- (AudioStreamBasicDescription)getAudioDescription {
AudioStreamBasicDescription audioDescription = {0};
audioDescription.mFormatID = kAudioFormatLinearPCM;
audioDescription.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;
audioDescription.mChannelsPerFrame = 1;
audioDescription.mBytesPerPacket = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mFramesPerPacket = 1;
audioDescription.mBytesPerFrame = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mBitsPerChannel = 8 * sizeof(SInt16);
audioDescription.mSampleRate = 44100.0;
return audioDescription;
}
- (void)setupIOUnit
{
try {
// Create a new instance of AURemoteIO
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
AudioComponent comp = AudioComponentFindNext(NULL, &desc);
XThrowIfError(AudioComponentInstanceNew(comp, &_rioUnit), "couldn't create a new instance of AURemoteIO");
// Enable input and output on AURemoteIO
// Input is enabled on the input scope of the input element
// Output is enabled on the output scope of the output element
UInt32 one = 1;
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &one, sizeof(one)), "could not enable input on AURemoteIO");
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &one, sizeof(one)), "could not enable output on AURemoteIO");
// Explicitly set the input and output client formats
// sample rate = 44100, num channels = 1, format = 32 bit floating point
CAStreamBasicDescription ioFormat = CAStreamBasicDescription(44100, 1, CAStreamBasicDescription::kPCMFormatFloat32, false);
// AudioStreamBasicDescription audioFormat = [self getAudioDescription];
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &ioFormat, sizeof(ioFormat)), "couldn't set the input client format on AURemoteIO");
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &ioFormat, sizeof(ioFormat)), "couldn't set the output client format on AURemoteIO");
// Set the MaximumFramesPerSlice property. This property is used to describe to an audio unit the maximum number
// of samples it will be asked to produce on any single given call to AudioUnitRender
UInt32 maxFramesPerSlice = 4096;
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(UInt32)), "couldn't set max frames per slice on AURemoteIO");
// Get the property value back from AURemoteIO. We are going to use this value to allocate buffers accordingly
UInt32 propSize = sizeof(UInt32);
XThrowIfError(AudioUnitGetProperty(_rioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, &propSize), "couldn't get max frames per slice on AURemoteIO");
_bufferManager = new BufferManager(maxFramesPerSlice);
_dcRejectionFilter = new DCRejectionFilter;
// We need references to certain data in the render callback
// This simple struct is used to hold that information
cd.rioUnit = _rioUnit;
cd.bufferManager = _bufferManager;
cd.dcRejectionFilter = _dcRejectionFilter;
cd.muteAudio = &_muteAudio;
cd.audioChainIsBeingReconstructed = &_audioChainIsBeingReconstructed;
AURenderCallbackStruct renderCallback;
renderCallback.inputProc = performRender;
renderCallback.inputProcRefCon = self;
XThrowIfError(AudioUnitSetProperty(_rioUnit, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 0, &renderCallback, sizeof(renderCallback)), "couldn't set render callback on AURemoteIO");
// Initialize the AURemoteIO instance
XThrowIfError(AudioUnitInitialize(_rioUnit), "couldn't initialize AURemoteIO instance");
}
catch (CAXException &e) {
NSLog(#"Error returned from setupIOUnit: %d: %s", (int)e.mError, e.mOperation);
}
catch (...) {
NSLog(#"Unknown error returned from setupIOUnit");
}
return;
}
Full source can be view at: http://pastebin.com/LXLYDEhy

Answer 1

Your code generally looks good from glancing at it, but there's at least one significant issue: instead of allocating space for the data to be copied into the buffers, you are explicitly setting them to NULL. Instead, you should allocate space and then copy it in with AudioUnitRender
Example code:
AudioBufferList *bufferList;
bufferList = (AudioBufferList *)malloc(sizeof(AudioBufferList) + sizeof(AudioBuffer));
bufferList->mNumberBuffers = 1;
bufferList->mBuffers[0].mNumberChannels = 1;
bufferList->mBuffers[0].mDataByteSize = 1024 * 4;
bufferList->mBuffers[0].mData = calloc(1024, 4);
(Note that you may need to adjust the allocation sizes to fit your stream type, size, etc -- the above is just example code, but it addresses your main issue.