It used DirectX because it uses the Hardware decoders and encoders provided by ATI, Intel or Nvidia.
DirectX12 has different 'feature levels'. It will work at DX 11, 10, 9 level if that's what software needs. In order to take fully advantage of the advanced computing capabilities the software needs to be re-written appropriately.
I have high hopes more from the new WDDM 2.0 included in Windows 10 that will allow for a better use of GPU multitasking powers. In previous models of WDDM, there are latency issues that limits that severely. This is a kernel component, more important than DirectX.
Of course, this won't happen automatically, software needs to be re-written.
https://en.wikipedia.org/wiki/Windows_Display_Driver_Model
http://www.anandtech.com/show/8962/the-directx-12-performance-preview-amd-nvidia-star-swarm/2
This message was edited 7 times. Last update was at Aug 09. 2015 09:53