There is a very useful (essential?) utility that comes with this package, in the examples/ subfolder, that allows you to integrate mplayer with this v4l2 loopback device. It's just a simple/single c file, "yuv4mpeg_to_v4l2". I really think it should get installed into the system with this package. (I.e. it seems to be necessary to get it to work with mplayer.) Reproducible: Always
I've introduced USE=examples to install such tools and codes. Thank you for your notice.