Andrew,

BUT I should have mentioned that there is a problem if the Settings->Preferences, Playback A, Video Driver is set to X11-OpenGL.  There appears to be some thrashing.  I have logged this in BT #434 and am hoping a Graphics guru can give us a hint of how to avoid this.  Using X11 driver works at really good hardware speed.  GG was looking at MPV to try to avoid this because according to the Forum topic "Multiple GPUs..." it works just fine there, as well as on the ffmpeg command line.  I searched on the internet and found no clues.   We are hoping there is some GL command to avoid the problem but we are not even close to GL experts.