Before Windows 11, DirectX 12 provided application- and driver-level interfaces to support GPU acceleration for several video applications, including:
Video decoding
Video processing
Motion estimation
Starting in Windows 11, D3D12 added a video encoding feature to the existing video API/DDI family. This feature provides a coherent set of encoding APIs/DDIs that are consistent with the existing D3D12 framework, and allows developers to perform video encoding using GPU-accelerated video engines.