Setting rate on AudioUnit subtype kAudioUnitSubType
I'm trying to get/set the rate of an AudioUnit with subtype kAudioUnitSubType_NewTimePitch .
The audio unit is added to an AUGraph , through an AUNode , which has the following component description:
acd->componentType = kAudioUnitType_Effect;
acd->componentSubType = kAudioUnitSubType_NewTimePitch;
acd->componentManufacturer = kAudioUnitManufacturer_Apple;
According to AudioUnitParameters.h , get/set the rate should be as simple as get/set the rate parameter on the audio unit.
// rate control.
// Global, rate, 1/32 -> 32.0, 1.0
kNewTimePitchParam_Rate = 0,
However, while setting the value seems no problem (no error is returned) getting the value yields a OSStatus with value -10878 (kAudioUnitErr_InvalidParameter) .
Here is how I set the value :
- (void)setTempo:(float)value {
OSStatus err = noErr;
err = AudioUnitSetParameter(tempoUnit, kNewTimePitchParam_Rate, kAudioUnitScope_Global, 0, (Float32)value, 0);
if (err != noErr) {
NSLog(@"Could not set tempo unit rate: %d", err);
} // no error
}
and how I (try to) get it :
- (float)tempo {
OSStatus err = noErr;
Float32 value = 1.0;
err = AudioUnitGetParameter(tempoUnit, kNewTimePitchParam_Rate, kAudioUnitScope_Global, 0, &value);
if (err != noErr) { // -10878
NSLog(@"Could not get tempo unit rate: %d", err);
}
return value;
}
The input of the node is connected to a mixer node, and the output to the RemoteIO unit.
Any ideas ?
It turns out the type of the Audio Unit was wrong.
I changed for kAudioUnitType_FormatConverter for the type and kept the same subtype.
Both get/set the tempo now works as expected.
I'm still unclear about why I didn't get any error, neither on setting up the audio unit, nor when setting the value for the rate.
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