I just recently reformatted(win 8.1 x64) and have the newest MPC-HC. I noticed that everytime I open a video file, or drag and drop a video to an instance of MPC already open, I get a heavy system lag spike that will freeze my mouse cursor in place for a half second, garble friends on discord for the same half second, ect. I have not made any changes to the default settings since installing and I don't remember this issue on my last install.
Could this be a GPU driver thing?
Looks like I may have discovered the issue. The default renderer "enhanced video renderer" seems to be the issue. If I select VMR9 the issue dissapears. I wonder if there is a way to have EVR with no lag?