you'll need node.js
run
npm install
run
npm run scroll [url] [width] [height] [stepsize] [deviceScaleFactor] [directory]
all parameters but must be in that order. They default to https://github.com, 512, 512, 25, 1, ./output/. stepsize defines how far a page is scrolled between taking screenshots.
you'll need ffmpeg.
run
cat output/*.png | ffmpeg -an -f image2pipe -i - -framerate 60 -vcodec libx264 -pix_fmt yuv420p -profile:v baseline -level 3 output.mp4
run
rm output/*.png