Title: Crop a video using ffmpeg
Author: Solène
Date: 20 December 2019
Tags: ffmpeg
Description: 

If you ever need to crop a video, which mean that you want to reduce
the area
of the video to a square of it to trim areas you don't want.

This is possible with ffmpeg using the video filter **crop**.
To make the example more readable, I replaced values with variables
names:

- WIDTH = width of output video
- HEIGHT = height of output video
- START_LEFT = relative position of the area compared to the left, left
being 0
- START_TOP = relative position of the area compared to the top, top
being 0

So the actual commands look like

    ffmpeg -i input_video.mp4 -filter:v
"crop=$WIDTH:$HEIGHT:$START_LEFT:$START_TOP" output_video.mp4


If you want to crop the video to get a 320x240 video from the top-left
position 500,100 the command would be

    ffmpeg -i input_video.mp4 -filter:v "crop=320:240:500:100"
output_video.mp4