This effect allows displacing, cropping, and/or scaling the source video horizontally and/or vertically. The In and Out parameters operate similar to the camera and projector functions in the Compositor:
Identical values for both In and Out that are less than the source dimension will simply crop the source. Different values will stretch (or compress if Out > In) the source in that direction (and crop if In is less than the source dimension).
This effect supports keyframes so these parameters can change smoothly over time. You can use this effect for many things such as having a cropped insert clip move across the screen, or have it change size or stretch while doing so. Be forewarned though, that for interlaced footage horizontal displacements are likely to destroy the field order, resulting in all sort of flickering and jumping movements.
The CINELERRA-GG Community, 2021