Blurring part of a video using ffmpeg

Hello, future Neil! You are probably trying to remember how you blurred part of a video. You blurred the bottom left portion of a circus video, using ffmpeg. You used: ffmpeg -i vid.mp4 -filter_complex "[0:v]crop=440:80:0:370,boxblur=2[mask];[0:v][mask]overlay=0:370[v]" -map "[v]" -map 0:a -c:a copy vid-with-blur.mp4 where: crop=440:80: this is the size of the boxblur, 440px wide, 80px high :0:370: this is the position of the boxblur, starting from left top. i.e. 0 pixels from the left, 370 pixels from the top boxblur=2: this is how dense the blurring is. 2 is quite weak; 10 is strong overlay=0:370: this needs to match the position of the boxblur