I'm afraid I did a bad job with this contribution.
I merged it into the development branch of the source tree a long time ago. My intention was to improve the implementation by using some features of the Sozi player that Robert didn't know about.
Unfortunately, I did not take the time to do it.
This work is still on my todo list.
Independently, Kai Wegner developed catchi with a different approach: instead of modifying the Sozi player, he developed a separate application that you can use to manage, annotate, and control Sozi presentations.