Crop selected area in all videos
Basic command is

ffmpeg -i in.mp4 -vf crop=iw:ih-25:0:0 -c:a copy out.mp4


Note that MP4s usually require the dimensions to be even, so the command above will actually crop 26 pixels from the bottom.

On linux, using bash, the script would be

#!/bin/bash
# Usage: ./crop.sh

mkdir cropped
for file in *.mp4;
do
    ffmpeg -i "${file}" -vf crop=iw:ih-25:0:0 -c:a copy "./cropped/$file"
done