Here’s how to resize videos and pictures using FFMPEG.

Bulk Resize Pictures

for filename in *.JPG; do 
  ffmpeg -i "$filename" -vf scale=-1:720 final/"$filename";
done

Bulk Resize Video and Create Thumbnail

for filename in *.MP4; do 
  ffmpeg -i "$filename" -s 1080x720 -pix_fmt yuv420p -crf 18 "$filename".mp4; 
  ffmpeg -ss 00:00:00 -i "$filename" -vframes 1 "$filename".jpg;
done