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How did the author do the actual zoom detection? (or rather, what is any method that can work for automating this?)

I'm sure it's not rocket science, but I don't know how to do this offhand.

there's a link at the bottom to the code (https://github.com/antiboredom/camera-motion-detector/). I use optical flow and then just count the percentage of pixels that appear to be moving away from the center. If that's bigger than ARBITRARY_THRESHOLD it's a zoom-in.

This was the only thing I was curious about, since the article was just leaping to conclusions and speculation.

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