DirectX question

Hi, quick question about DirectX. I have 11, have been told to download 9c. Do I need to add 9c or does 11 supersede 9c?

The background is I have Corel Video Studio Pro X4. Since day one the previewing of the edited videos (before outputting to an actual video file) have been choppy as all hell and sometimes the video part of it would stall all together while the audio kept going without issue. At first I thought it was my crappy camera, so I finally replaced that, only to have the same issue. I contacted Corel, they had me run DxDiag and provide that to them, along with wanting to know my computer's specs and updating QuickTime. I provided that. DxDiag shows that I have DirectX 11, but they just sent me a link to download Dx 9c from Microsoft along with instructions to uninstall and reinstall Video Studio. So now I'm confused, do I need 9c as well as 11 or are they just covering all bases?

Thanks in advance.

 

Nevermind, I tried installing 9c and it wouldn't let me as I had a more up to date version.

Thanks for looking.