AVC Plugin is a plug-in that utilizes the system.framework bundle, in addition to a bundle that was developed together with this plug-in. On OSX AVC devices (i.e. camcorders, etc.) are represented in the IORegistry as instances of IOFireWireAVCUnit.
The AVCbundle.bundle, developed with Project Builder, is a shared library; the plugins CFM runtime requires the MachO runtime the AVCbundle provides. Most of the work is done by the MachO bundle, which delivers a callback function the FWNotification class implements.