I’m a CoreAudio beginner and I got tripped up over this one. Hopefully this post (and radar bug) will improve error reporting in future releases of Apple’s audio queue services API.
Here’s the problem: we’re supposed to use the AudioQueueSetProperty API when associating a AudioQueueRef with an AudioObject. Instead of passing the AudioDeviceID of the device, we’re supposed to pass the device unique id, a pointer to a CFStringRef.
The call to AudioQueueSetProperty will succeed regardless of the CFStringRef's value
What does that mean? That means you’ll fail later in your application if you’ve passed a bad value to AudioQueueSetProperty
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AudioQueueRef audioQueue = ...; CFStringRef garbageUID = (CFStringRef)@"Garbage!"; OSStatus status = AudioQueueSetProperty(audioQueue, kAudioQueueProperty_CurrentDevice, &garbageUID, sizeof(CFStringRef)); // status is still noErr ... // Sometime later UInt32 cookieSize; status = AudioQueueGetPropertySize (audioQueue, kAudioQueueProperty_MagicCookie, &cookieSize); // And now status is kAudioQueueErr_InvalidDevice |