Core Audio Swift Equalizer adjusts all bands at once? - ios

Question

I am having trouble setting up a kAudioUnitSubType_NBandEQ in Swift. Here is my code to initialize the EQ:
var cd:AudioComponentDescription = AudioComponentDescription(componentType: OSType(kAudioUnitType_Effect),componentSubType: OSType(kAudioUnitSubType_NBandEQ),componentManufacturer: OSType(kAudioUnitManufacturer_Apple),componentFlags: 0,componentFlagsMask: 0)
// Add the node to the graph
status = AUGraphAddNode(graph, &cd, &MyAppNode)
println(status)
// Once the graph has been opened get an instance of the equalizer
status = AUGraphNodeInfo(graph, self.MyAppNode, nil, &MyAppUnit)
println(status)
var eqFrequencies: [UInt32] = [ 32, 250, 500, 1000, 2000, 16000 ]
status = AudioUnitSetProperty(
self.MyAppUnit,
AudioUnitPropertyID(kAUNBandEQProperty_NumberOfBands),
AudioUnitScope(kAudioUnitScope_Global),
0,
eqFrequencies,
UInt32(eqFrequencies.count*sizeof(UInt32))
)
println(status)
status = AudioUnitInitialize(self.MyAppUnit)
println(status)
var ioUnitOutputElement:AudioUnitElement = 0
var samplerOutputElement:AudioUnitElement = 0
AUGraphConnectNodeInput(graph, sourceNode, sourceOutputBusNumber, self.MyAppNode, 0)
AUGraphConnectNodeInput(graph, self.MyAppNode, 0, destinationNode, destinationInputBusNumber)
and then to apply changes in the frequency gains my code is as follows:
if (MyAppUnit == nil) {return}
else{
var bandValue0 :Float32 = tenBands.objectAtIndex(0) as! Float32
var bandValue1 :Float32 = tenBands.objectAtIndex(1) as! Float32
var bandValue2 :Float32 = tenBands.objectAtIndex(2) as! Float32
var bandValue3 :Float32 = tenBands.objectAtIndex(3) as! Float32
var bandValue4 :Float32 = tenBands.objectAtIndex(4) as! Float32
var bandValue5 :Float32 = tenBands.objectAtIndex(5) as! Float32
AudioUnitSetParameter(self.MyAppUnit, 0, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue0, 0);
AudioUnitSetParameter(self.MyAppUnit, 1, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue1, 0);
AudioUnitSetParameter(self.MyAppUnit, 2, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue2, 0);
AudioUnitSetParameter(self.MyAppUnit, 3, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue3, 0);
AudioUnitSetParameter(self.MyAppUnit, 4, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue4, 0);
AudioUnitSetParameter(self.MyAppUnit, 5, AudioUnitScope(kAudioUnitScope_Global), 0, bandValue5, 0);
}
Can anyone point out what I am doing wrong here? I think it is related to the second variable in AudioUnitSetParameter. I have tried AudioUnitParameterID(0), and AudioUnitParameterID(kAUNBandEQParam_Gain + 1) for this Value but those don't seem to work at all. Any help is appreciated!

Answer 1

Comment adding as answer because comments are insufficient.
The following Code is in Objective-c but it should help identify your problem.
There are a number of places this might fail. Firstly, you should check the status of the AudioUnitSetParameter, and indeed all the AudioUnit Calls as this will give you a clearer point of where you're code is failing.
I've done this successfully in Objective-C and have a test app i can make available, if you need it, which shows the complete graph setup and setting the bands and gains by moving a slider ... back to your specific question. The following works just fine for me, this might help you rule out a particular section.
You can try and obtain the current "gain", this will indicate if your bands are set up correctly.
- (AudioUnitParameterValue)gainForBandAtPosition:(uint)bandPosition
{
AudioUnitParameterValue gain;
AudioUnitParameterID parameterID = kAUNBandEQParam_Gain + bandPosition;
OSStatus status = AudioUnitGetParameter(equalizerUnit,
parameterID,
kAudioUnitScope_Global,
0,
&gain);
if (status != noErr) {
#throw [NSException exceptionWithName:#"gettingParamGainErrorException"
reason:[NSString stringWithFormat:#"OSStatus Error on getting EQ Gain! Status returned %d).", (int)status]
userInfo:nil];
}
return gain;
}
then setting the gain can be done in the following way;
- (void)setGain:(AudioUnitParameterValue)gain forBandAtPosition:(uint)bandPosition
{
AudioUnitParameterID parameterID = kAUNBandEQParam_Gain + bandPosition;
OSStatus status = AudioUnitSetParameter(equalizerUnit,
parameterID,
kAudioUnitScope_Global,
0,
gain,
0);
if (status != noErr) {
#throw [NSException exceptionWithName:#"settingParamGainAudioErrorException"
reason:[NSString stringWithFormat:#"OSStatus Error on setting EQ gain! Status returned %d).", (int)status]
userInfo:nil];
}
}
Finally, what value are you trying to set, the valid range (if I'm not mistaken) is -125.0 to 25.0