In theory, the developers of the d-cinema system have considered everything into one smooth hands-free operation. But as the philosopher Yogi Berra says, "In theory, there is no difference between theory and practice. In practice there is."
When things go wrong, you need to describe the problem with some intelligence to the people who are going to assist you in solving the problem. Missing one movie is worth hundreds or thousands of money units. But it isn't only movies that you are showing.
Digital cinema projectors can show many different types of entertainment from many different sources. If the mechanism of getting the proper version of a movie and keys is complicated, alternative content sources all bring the same plus additional complexity: different boxes, different cables, different aspect ratios, different sound mixes.
the possibilities are nearly endless, each one with different potential and different expectations...and different boxes and connectors, different potential points of failure.
Alternative content comes with many standards. This course gives you the fundamentals to be conversant with them.