Wow I stumbled across this question because I have the answer to it (and was looking for an easy way to incorporate 2d flat video into a 3d one).
The answer is IW3 which generates a 3d video after depth mapping the 2d source and adjusting the video. (Full sbs works with vr headsets, Half sbs works with 3d TVs)
It is free software that is bundled on GitHub with nunif.