What are the best codecs and formats for importing video?

I've been trying to figure this out for months now, and there seems to be very little helpful information out there!

I know that Unity supports the same formats as Quicktime (which needs to be installed) and that Unity automatically converts video files to Ogg Theora,but the only format ive been able to successfully imort to unity was a .mpg file using the "MPEG-4 video (mp4v)" codec.

All of the other file formats I've tried have failed, even the other .mpg files!

Adobe After Effects will only render this format out as high as 720x576, as far as I can gather.

How do I get HD video into unity???? (I'm using v4.6.1)

p.s. I have also tried pre-formatting my files to ogg theora using other software with no success!