I have a movie, and I want to produce a new movie out of it with an area blurred (e.g. an object, a writing or a face). The area is moving, so I must have fine control of the current frame and move the position of the blur area accordingly. Blur is an option, but also a dark mask is fine too.
Now, I have a question open at superuser on which software to use, but since I suspect I will have to buy adobe premiere to do something like this, and I don't want to shell out a kidney for something I have to do once, I am thinking about coding it myself in python.
What are the best libraries available for this task ?