Comment by dekhn
Interesting. Yes, I assume that's possible although I'm not sure how you handle the background- I guess you find an empty frame, and subtract that from every image with a plane.
One of the advantages of working with image data is that movies are really just 3d data and as long as all the movies you work with are the same size, if you have enough ram, or use dask, you could basically do this in a couple lines of numpy.
You could do an add operation if the background is dark enough, or yeah, take a local sample of the background to subtract from each clip, and choose a specific background...