iOS RemoteIO - AudioUnitAddRenderNotify Callback - core-audio

Question

I'm trying to do a recording from RemoteIO using AudioUnitAddRenderNotify like this.
Basically, I'm not able to get the samples from bus1, which is my input bus. The recordingCallback does not go past this :
if (*ioActionFlags & kAudioUnitRenderAction_PostRender || inBusNumber != 1) {
return noErr;
}
But I was told that the recordingCallback should be called for each bus every round. ie. called with inBusNumber ==0, then inBusNumber ==1, which are the output (remoteIO out) and input (recording bus) respectively.
What can I do to get recordingCallback to be called on my input bus so that I can record?
Thanks.
Pier.
Here's the callback.
static OSStatus recordingCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
NSLog(#"Entered recording callback");
// Only do pre render on bus 1
if (*ioActionFlags & kAudioUnitRenderAction_PostRender || inBusNumber != 1) {
return noErr;
}
RIO *rio = (RIO*)inRefCon;
AudioUnit rioUnit = rio->theAudioUnit;
//ExtAudioFileRef eaf = rio->outEAF;
AudioBufferList abl = rio->audioBufferList;
SInt32 samples[NUMBER_OF_SAMPLES]; // A large enough size to not have to worry about buffer overrun
abl.mNumberBuffers = 1;
abl.mBuffers[0].mData = &samples;
abl.mBuffers[0].mNumberChannels = 1;
abl.mBuffers[0].mDataByteSize = inNumberFrames * sizeof(SInt16);
OSStatus result;
result = AudioUnitRender(rioUnit,
ioActionFlags,
inTimeStamp,
inBusNumber,
inNumberFrames,
&abl);
if (noErr != result) { NSLog(#"Obtain recorded samples error! Error : %ld", result); }
NSLog(#"Bus %ld", inBusNumber);
// React to a recording flag, if recording, save the abl into own buffer, else ignore
if (rio->recording)
{
TPCircularBufferProduceBytes(&rio->buffer, abl.mBuffers[0].mData, inNumberFrames * sizeof(SInt16));
//rio->timeIncurred += (('p'float)inNumberFrames) / 44100.0;
//NSLog(#"Self-calculated time incurred: %f", rio->timeIncurred);
}
return noErr;
}
Here's the code which calls the callback.
- (void)setupAudioUnitRemoteIO {
UInt32 framesPerSlice = 0;
UInt32 framesPerSlicePropertySize = sizeof (framesPerSlice);
UInt32 sampleRatePropertySize = sizeof (_graphSampleRate);
// 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, &_remoteIOUnit);
if (noErr != status) { NSLog(#"Get audio units error"); return; }
// Enable IO for recording
UInt32 flag = 1;
status = AudioUnitSetProperty(_remoteIOUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
kInputBus,
&flag,
sizeof(flag));
if (noErr != status) { NSLog(#"Enable IO for recording error"); return; }
// Enable IO for playback
status = AudioUnitSetProperty(_remoteIOUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
kOutputBus,
&flag,
sizeof(flag));
if (noErr != status) { NSLog(#"Enable IO for playback error"); return; }
// Obtain the value of the maximum-frames-per-slice from the I/O unit.
status = AudioUnitGetProperty (
_remoteIOUnit,
kAudioUnitProperty_MaximumFramesPerSlice,
kAudioUnitScope_Global,
0,
&framesPerSlice,
&framesPerSlicePropertySize
);
// Describe format
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(_remoteIOUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
kInputBus,
&audioFormat,
sizeof(audioFormat));
if (noErr != status) { NSLog(#"Apply format to input bus error"); return; }
status = AudioUnitSetProperty(_remoteIOUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&audioFormat,
sizeof(audioFormat));
if (noErr != status) { NSLog(#"Apply format to output bus error"); return; }
rio.theAudioUnit = _remoteIOUnit; // Need this, as used in callbacks to refer to remoteIO
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = &rio;
status = AudioUnitAddRenderNotify(_remoteIOUnit, callbackStruct.inputProc, callbackStruct.inputProcRefCon);
NSAssert (status == noErr, #"Problem adding recordingCallback to RemoteIO. Error code: %d '%.4s'", (int) status, (const char *)&status);

Answer 1

I managed to resolve this by not using AudioUnitAddRenderNotify, and by using the following code.
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = &rio;
status = AudioUnitSetProperty(_remoteIOUnit,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Global,
kInputBus,
&callbackStruct,
sizeof(callbackStruct));
if (noErr != status) { NSLog(#"Set input callback error"); return; }
on the input bus instead