>The potential amount of encodable data is larger than the file size of the image itself! Screw secret messages, we’re literally creating data storage out of nothing!

Uh, nope. The file is small because the frames are non random, and thus heavily compressed. If you wanted to store arbitrary data, the frames would be far more random, and therefore take up more space.

(The above was written halfway through the article)

I disagree that you need "deep knowledge of how image compression works". I have very little idea how the actual compression works, the only thing I needed to know was that images are compressed and random/arbitrary data doesn't compress as well for fundamental algorithmic reasons. It's obvious that changing images can make them larger even without any knowledge of the particular compression used.