View source for VLC HowTo/Crop

If you want to crop local video with command-line parameters, use
 vlc input --vout-filter=crop --crop-geometry=120x120+10+10
120x120 is the wanted resolution (in pixels), and 10+10 is the position where the cropping should start (in pixels)

or if you want certain aspect ratio
 vlc input --vout-filter=crop --crop-ratio=1777
where 1777 is aspect ratio you want (divide it with 1000 to get correct value, in this case 1,777 aka 16:9)