I have some videos that I recorded in very high quality and ended up being too heavy. To save some space I decided to resize them and I found this can be easily done with ffmpeg.
To install ffmpeg:
1 sudo apt install ffmpeg
Then, we just need one command to change the resolution of a video:
1 ffmpeg -i input.mp4 -vf scale=-1:720 output.mp4
The scale argument means the output video will have a width of 720px and the height will be set based on the ratio of the original video.