It would be nice if you could crop during playback, for example I have a couple recorders that record 4x3 resulting in letterboxed video (black bar top and bottom) for 16x9 sources. if I try to play back fullscreen on a widescreen monitor the letterboxed 4x3 video gets pillarboxed (black bars on both sides) so the actual video ends up about 70% of the size it could be if the bars could be cropped.
you can crop by using the w key or the +/- key.