WiDi is now practically Miracast, a WiFi Alliance Standard.
On PC, the wifi direct channel will be the same channel that your PC uses to connect to the network. So, interferences are not from your own network but from your neighbor's. Try change your router's channel to see if it makes a difference. Also, Miracast is still in its infancy. Adapter's quality vary a lot.
Remember, videos are decoded on the PC, then re-encoded into H.264 by the graphics card and send over wifi direct to the Miracast adapter. The PQ will always suffer this way. Make sure your graphics driver and wifi driver are up to date.