Turns out output to video suffers from loss of quality problems when in
color (not grayscale). It may be better in some cases to just output
each frame as a png and combining them later with ffmpeg like how it is
mentioned here: https://trac.ffmpeg.org/wiki/Slideshow . Grayscale video
is noticably better, but both cases result in large video sizes, so care
may be needed if free disk-space is sparse.
