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Re: Coreaudio-api Digest, Vol 3, Issue 193

Ah, looking back I see you posted this among other code an earlier email. Sorry for missing it.

One thing to check: your earlier code sample includes the line

err = AUGraphInitialize(auGraph);

after you try to set the device and enable IO. I believe this must be done before setting the device properties of the AUHAL unit.


I also notice that you were not setting the number of busses for the Mixer. I'm not sure this matters, as it may be 1 by default, but in my use of the mixer I include the following during setup (error checks removed):

UInt32	numbuses;

numbuses = 1;
AudioUnitSetProperty(	_outMixerUnit,
			kAudioUnitProperty_BusCount,
			kAudioUnitScope_Input,
			0,
			&numbuses,
			sizeof(UInt32) );
		
numbuses = 1;	
AudioUnitSetProperty(	_outMixerUnit,
			kAudioUnitProperty_BusCount,
			kAudioUnitScope_Output,
			0,
			&numbuses,
			sizeof(UInt32) );



On Jun 21, 2006, at 3:03 PM, email@hidden wrote:

Part 2)
In answer to two other questions regarding setting the volume on the
mixer.   Yes, I do do this.   I'm using code gleaned from
MatrixMixerTest, which does:
- (void) setVolumes {
	OSStatus err = AudioUnitSetParameter(mixerUnit,
kMatrixMixerParam_Enable, kAudioUnitScope_Input, 0, 1, 0);
	checkErr(err);
	err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Enable,
kAudioUnitScope_Output, 0, 1, 0);
	checkErr(err);


	// Set global volume
	err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume,
kAudioUnitScope_Global, 0, 1, 0);
	checkErr(err);


As a sidenote, here's a sample function I use to set crosspoint volumes:

- (OSStatus) setCrosspointVolume: (float) volume atInput: (UInt32) input atOutput: (UInt32) output
{
OSStatus err = noErr;

if ([self validInputChannel:input] && [self validOutputChannel:output]) {
UInt32 element = (input << 16) | (output & 0x0000FFFF);
err = AudioUnitSetParameter( _outMixerUnit,
kMatrixMixerParam_Volume,
kAudioUnitScope_Global,
element,
volume,
0);
} else {
err = INVALID_CHANNEL;
}

return err;
}



	
	// Set master volume
	err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume,
kAudioUnitScope_Global, 0xFFFFFFFF, 1, 0);
	checkErr(err);
	
	// Set input and output volumes
	err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume,
kAudioUnitScope_Input, 0, 1, 0);
	checkErr(err);
	err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume,
kAudioUnitScope_Output, 0, 1, 0);
	checkErr(err);
}





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