ffmpeg has been proven to be stable for our needs (extract video thumbnails, get duration of videos).
At the same time, mplayer has lost traction and mplayer2 is abandoned. mpv seems to be what mplayer2 once was, but we already have ffmpeg support and ffmpeg is reasonably wide-spread among distros.
- Remove mplayer support
- Review video thumbnails (do we really need to extract several images per time-step?)