is described as the libavcodec library from the FFmpeg project provides many of VLC's codecs, but the player mainly uses its own muxers and
Then there is
which is described as free and open-source media player software based on MPlayer, mplayer2 and FFmpeg.
VLC seems to include a GIU. Apparently, it uses QT4 for Linux. While MPV is still primarily a command-line application and there are a number of GUI front-ends available.
I notice that these days the Ubuntu Mate distro includes
(formerly GNOME MPV) - for Linux - based on GTK, written in C. Its goal is to be a simple GTK-based graphical interface for
that meets the GNOME Human Interface Guidelines.
Makes me wonder if MPV is now becoming more popular than VLC ???