Utility software
FFMpeg (macOS, Linux, Win) ***
FFMpeg is a swiss-army knife for playing and streaming video and audio. Visual node-based editor for FFMPeg, Freemium. - https://ffmpeg.guide/ FFMpeg CLI snippets, from video archivists. - https://amiaopensource.github.io/ffmprovisr/ https://github.com/jeanslack/Videomass
HandBrake (macOS, Linux, Win) ***
Open Source Video transcoder https://github.com/HandBrake/HandBrake
MPV (macOS, Linux, Win) ***
MPV is a video player library, like FFMpeg. It has several GUI for different platforms. It is very scriptable Windows - https://github.com/mpvnet-player/mpv.net
Shutter Encoder (macOS, Linux, Win) ***
Graphical frontend for FFMpeg to convert video, images, and audio.
VLC
Multi-platform video playing / streaming swiss army knife.
https://linuxkamarada.com/en/2019/08/31/vlc-how-to-play-fullscreen-on-second-monitor-while-keeping-controls-on-first-monitor/ ProjectM is an audio visualizer that is FFMpeg compatible.