Accessing Events from Video Device

I have an intra-**** video device that's supported by Apple's AVCaptureDevice. I can use the AV classes to connect to the device and get video. However, this device has a button that's used to acquire still images from the video stream. I can't use the IOUSBDeviceInterface to do an asynchronous read, because the Apple driver has the device opened exclusively. How do I go about receiving the button event in this scenario? I know which pipe to read, based on a bus analyzer when I run this on Windows, I just need to know how to access that pipe when the device is opened by another process.

Accessing Events from Video Device
 
 
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