remoteIO unit not entering input callback in AUGraph
remoteIO unit not entering input callback in AUGraph
- Subject: remoteIO unit not entering input callback in AUGraph
- From: Alex Wiltschko <email@hidden>
- Date: Thu, 28 Jan 2010 22:48:39 -0500
Hello all,
I've finished an app using Audio Units to acquire audio directly from the mic. I'm in the process of converting my code to use AUGraphs, so that I can stick in a mixer eventually.
My problem is, using an AUGraph, the render callback is never being entered.
I've stuck with Apple's example code closely, and I can't quite get it to work. The code posted below was modified only slightly to use a graph instead of a single unit, so I'm baffled as to what is not working.
Here's what I'm doing:
// Setting up the Audio Session...
// Initialize and configure the audio session, and add an interuption listener
AudioSessionInitialize(NULL, NULL, sessionInterruptionListener, self);
UInt32 audioCategory = kAudioSessionCategory_PlayAndRecord;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(audioCategory), &audioCategory);
// Allow iPod audio to continue to play while the app is active.
UInt32 flag = 1;
AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(flag), &flag);
// Add a property listener to listen to changes to the session
AudioSessionAddPropertyListener(kAudioSessionProperty_AudioRouteChange, sessionPropertyListener, self);
Float32 preferredBufferSize = 0.00125;
AudioSessionSetProperty(kAudioSessionProperty_PreferredHardwareIOBufferDuration, sizeof(preferredBufferSize), &preferredBufferSize);
//set the audio session active
AudioSessionSetActive(YES);
OSStatus err;
// Now start setting up the graph & nodes
//create the graph & its only node, which will be of type remoteIO
NewAUGraph(&graph);
AUNode ioNode;
// First describe the node, graphs are made up of nodes connected together, in this graph there is only one node.
// the descriptions for the components
AudioComponentDescription outputDescription;
outputDescription.componentFlags = 0;
outputDescription.componentFlagsMask = 0;
outputDescription.componentType = kAudioUnitType_Output;
outputDescription.componentSubType = kAudioUnitSubType_RemoteIO;
outputDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
// Create the remoteIO node, and open the graph
err = AUGraphAddNode(graph, &outputDescription, &ioNode);
NSAssert(err == noErr, @"Failed to add the remoteIO node");
err = AUGraphOpen (graph);
NSAssert(err == noErr, @"Opening the audio graph failed");
// Grab an instance of the remoteIO unit from the graph
AudioUnit ioUnit;
err = AUGraphNodeInfo(graph, ioNode, NULL, &ioUnit);
NSAssert(err == noErr, @"NOOO! (couldn't get the node info)");
// Set the audio format on the audio unit instance
AudioStreamBasicDescription audioFormat;
memset(&audioFormat, 0, sizeof(audioFormat));
// Let's talk formats for just a sec
audioFormat.mSampleRate = 44100.0f;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kAudioFormatFlagsCanonical;
audioFormat.mFramesPerPacket = 1;
audioFormat.mChannelsPerFrame = 1;
audioFormat.mBitsPerChannel = 16;
audioFormat.mBytesPerPacket = 2;
audioFormat.mBytesPerFrame = 2;
// set the format on the bus coming into the app ...
err = AudioUnitSetProperty(ioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
kInputBus,
&audioFormat,
sizeof(audioFormat));
NSAssert(err == noErr, @"Error setting Output Scope for Bus 1 (from microphone to app)");
// ... and on the bus leaving the app for the mic
err = AudioUnitSetProperty(ioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&audioFormat,
sizeof(audioFormat));
NSAssert(err == noErr, @"Error setting Input Scope for Bus 0 (from app to mic)");
// Enable IO from the mic to the app...
UInt32 one = 1;
err = AudioUnitSetProperty(ioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
kInputBus, // BUS 1
&one,
sizeof(one));
NSAssert(err == noErr, @"Could not enable the Input Scope of Bus 1");
// ... and from the app back out to the mic
err = AudioUnitSetProperty(ioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
kOutputBus, // BUS 0
&one,
sizeof(one));
NSAssert(err == noErr, @"Could not enable the Output Scope of Bus 0");
// This is what doesn't seem to be working
// ***********************************
AURenderCallbackStruct playbackCallbackStruct;
playbackCallbackStruct.inputProc = continuousDisplayOutputCallback;
continuousCallbackData *cd = (continuousCallbackData *)malloc(sizeof(continuousCallbackData));
cd->ssb = secondStageBuffer;
cd->au = &outputAudioUnit;
playbackCallbackStruct.inputProcRefCon = cd;
// Register a callback with the AUNode
err = AUGraphSetNodeInputCallback (graph,
ioNode,
kInputBus,
&playbackCallbackStruct);
// continuousDisplayOutputCallback() is never entered! I have an NSLog; return; right at the beginning,
// and the app sits silent after initialization, and no audio is acquired.
// ***********************************
// Now we get to start it all up!
err = AUGraphInitialize(graph);
NSAssert(err == noErr, @"Could not initialize audio graph");
err = AUGraphStart(graph);
NSAssert(err == noErr, @"Could not start audio graph");
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