I have a fx factory plugin called "frame info" it's telling me my video is Interlaced which I was sure it was Progressive according to Mpeg streamclip. How can I tell if the video is progressive or interlaced?
If you have a horizontal move, you should see the interlace lines.
The info in the clip could be meaningless, as it is a flag that can be set by anyone to their liking.
The only way to be sure is to check it visually, or knowing the source and history.
(eg, 5d material is always progressive, as the cam can't shoot otherwise. But if it was shot at 24P and someone added pulldown, it will be interlaced...)