regarding dxva2 driver

Dear Experts,

We are trying to understand what components to be written for such a

The device does h.264 decoding. This plugs over PCI and is not a display
card, but can only decode different kinds of video like h.264.

We understood that the Windows Media Foundation Transforms with hardware
decoding to be written.

Should we write a MFT talking using DXVA2 driver or can the MFT directly
call the device through some proprietary interface? DXVA2 driver is
closely tied to display driver. How will this work?

Please help in understanding this.