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 demuxers.
Then there is MPV<https://en.wikipedia.org/wiki/Mpv_(media_player)>
described as free and open-source media player software based on MPlayer, mplayer2 and
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 MPV that meets the GNOME Human Interface Guidelines.
Makes me wonder if MPV is now becoming more popular than VLC ???