I remember years ago there was a request to implement GMICs in CinGG.
The answer was that they were too heavy and would slow down the
program too much. They are actually better suited for still images
than video. A morphing filter would be nice, though.
I think G'MIC itself can read/write some videos IF compiled with OpenCV support (and OpenCV in turn compiled with video support)
Also, Igor posted interesting video I only saw today
"Alpha Track Matte with the Reroute and Chroma Key effects in Cinelerra."