How to use the input tab

Open input movie
Interlace

Open input movie

The input tab is where you open the movie(s) to be processed.
You can clear a movie by clicking "Choose" then clicking "Cancel".
The Movies Diff feature is the only one that needs two input movies (unless you want to make an edge movie).
If only one movie is open it will be used. If two are open and only one is needed the first is used.

Interlace

In some cases we need to know if the movie is interlaced (not progressive). Most video is interlaced, including most DV and MPEG2. Look for the tell-tale comb structure at the edges of horizontally moving objects.
DV video is "bottom field first" meaning that the picture consisting of lines 2,4,6,...,480 of the video frames is 1/60 second earlier than the picture consisting of lines 1,3,5,...,479.
HD video is top field first.