After capturing a session and an mpeg is produced, there is a "Play" button offered in a "Capture results" window. Clicking this button attempts to run mplayer (src/app_data.c line #407). Note that this is just a convenience thing, your movie is still available, and you can click the "close" button to dismiss the results window. I'm going to guess that this means that mplayer should be a dependency, or a patch of some sort should be made for the code? Reproducible: Always This may effect earlier versions of this program, but I can only get this version to build.
I will add an elog message to the ebuild for 1.1.7 release. See bug #234383.