static-captcha/run.sh

#!/bin/bash

FPS=30
DURATION=5
COMPRESSION=40

X=400
Y=150

# Create the mask
convert \
	-background none -fill black \
	-pointsize 120 -size ${X}x${Y} -gravity center \
	label:$1 mask.png

# Create large static image
convert -size 2000x${Y} canvas: +noise Random -monochrome -alpha off background.png

# Create video
ffmpeg -loglevel error -hide_banner -y -framerate $FPS -loop true -t $DURATION -i background.png -i mask.png \
	-filter_complex "
		[0] crop=x=n:w=${X}:h=${Y},split[bg][a];
		[a] hflip,vflip [flip];
		[1] alphaextract [mask];
		[flip][mask] alphamerge [text];
		[bg][text] overlay"\
	-c:v libx264 -crf $COMPRESSION -an out.mp4

rm mask.png background.png