How can I get the handle to the DXVA-2 decoder device?

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C++

directshow

There is a structure in MSDN:

typedef struct _D3DAUTHENTICATEDCHANNEL_CONFIGURECRYPTOSESSION {
 D3DAUTHENTICATEDCHANNEL_CONFIGURE_INPUT Parameters;
 HANDLE                                  DXVA2DecodeHandle;
 HANDLE                                  CryptoSessionHandle;
 HANDLE                                  DeviceHandle;
} D3DAUTHENTICATEDCHANNEL_CONFIGURECRYPTOSESSION;

And about the parameter:

DXVA2DecodeHandle: A handle to the DirectX Video Acceleration 2 (DXVA-2) decoder device.

So far I can only get the IDirectXVideoDecoder pointer.
Do anybody know how I can get the handle to decoder device?