I took some time today to get the event loop working. The loop itself was quite straightforward; recognition of the exact event types took some more time.
My next step will be to rebuild a macro for the event loop, much like the one in cl-sdl. The complete hand-written version I have now is not very user-friendly. But at least I can see all the details of how to set it up.
Other note: I still have to take another look at querying the video info. And I have to package everything up using asdf.