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The operating system requires a GFX driver to meet the same requirements for handling DRM-protected content as any other driver in the WDM audio system. In order to support DRM (digital rights management), the GFX/AVStream filter implements a property handler for KSPROPERTY_DRMAUDIOSTREAM_CONTENTID. This handler calls DrmForwardContentToDeviceObject to advise the DRMK system driver of the connected downstream pin that receives the content. The GFX/AVStream filter calls KsPinGetConnectedPinFileObject and KsPinGetConnectedPinDeviceObject to retrieve the FILE_OBJECT and DEVICE_OBJECT parameters to pass to DrmForwardContentToDeviceObject.