When Android Studio registers videos, it includes the status and bottom bar. Usually they are not terribly important to show the app’s core business, and they also take space to be encoded. ffmpeg can help to optimize app video previews.

The command I usually use (for example for ‘Weight’) to crop them is

ffmpeg -i in.mp4 -filter:v "crop=640:1134:0:50" -an out.mp4

It takes the in.mp4 video, and selects an area whose size is 640x1134 pixels located on the left edge (the 0 in the crop numbers), and 50 pixels from the top edge. The flag “-an” removes the audio track.