Import video in cubase 6.5.5

Hi everyone, for the first time I find myself having to work in syncro with video in cubase 6.5.5, but I can’t import any video format. I use windows 7. I have updated the codecs but nothing. If I have not misunderstood according to the instructions of steinberg it is necessary to purchase Video Decoder for Avid DNxHD®, is it correct? Do you know? Thank you.