Machine Learning in FAST corner detector

This paper by Edward Rosten and Tom Drummond 2008 describes choosing interest point via machine learning approach using ID3 algorithm. I understand the concept of the ID3 they are using. But my question is how are they fitting this whole training and testing idea of machine learning, while are analysing real time video frame.

Your question is not clear, but I'll try to answer. They dont analyze "real time video frame" with machine learning. What do they do: