Having a hell of a time trying to get mmal to work still just following the wiki. For those who have this working, do you get a result when you run ffmpeg -codecs | grep mmal ? Thats something that seemed needed previously but I cannot get it to show up with --enabled-shared on. And no matter what I do and recompiling Attractmode each time, I can't get MMAL to show up on the decoder menu. Is there any dependencies that might not be listed or.. I don't know, things I should remove? This is an oldish setup (Everything is up to date, but its seen endless amounts of tweaking and testing and package removal and reinstallation so I imagine there could be something small and stupid I'm missing)
Make sure you have removed any previous ffmpeg or libav packages you may have installed previously before building ffmpeg yourself. It might be that you have a conflicting ffmpeg package that attractmode is linking to
To confirm what ffmpeg attract-mode is getting, run
attract --version
and compare the version of avcodec against the version of ffmpeg that you are compiling with mmal enabled
hope this helps