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what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err?

Subject: what would cause QTSetComponentProperty to fail with a kAudioUnitErr_InvalidPropertyValue err?
From: Michael Dautermann <email@hidden>
Date: Fri, 9 Mar 2007 16:09:01 -0800
Delivered-to: email@hidden
Delivered-to: email@hidden

Hi all,

The answer to this should be staring me in the face but it's escaping my notice.

I'm putting together a new Audio Hardware plugin. I'm very thankful for the JackRouter project (THANKS Stéphane!) but oh how I wish there were more sample code & projects to rely on.

Under DeviceGetPropertyInfo, I set the size of the kAudioDevicePropertyDeviceUID property to CFStringRef and for DeviceGetProperty, I'm returning my device uid properly using:

*outString = CFStringCreateWithCString(kCFAllocatorDefault, "MyNiftyDevice:0", CFStringGetSystemEncoding());

I can see these properties and the UID of my plugin just fine when I examine it under HALLabs.

But when I try to set the Sequence Grabber in my application to pick it up (via QTSetComponentProperty, using the same format as WhackedTV):

err = [self setPropertyWithClass: kQTPropertyClass_SGAudioRecordDevice id: kQTSGAudioPropertyID_DeviceUID size: sizeof(uid) address: &uid];

this fails with a kAudioUnitErr_InvalidPropertyValue.

Anyone have any ideas off the top of their head what I might be missing?

p.s. as an aside, WhackedTV passes an NSString in for the UID and that NSString's "sizeof" byte count doesn't match the byte count for the [ NSString length ]. Should I be surprised this works for Apple sample code?

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