Best option(s) for chroma key

I need to overlay a video with alpha on top of another video in Unity. After some digging I think my best option is to composite the video so the transparent areas are green and then use chroma key asset or shader to make the green areas transparent. Has anyone tried this? Is my best option to purchase an asset from the asset store or to write my own custom shader or?

I don’t know about inside Unity, but in general Chroma Keying sounds more expensive (in terms of cpu/gpu) since its trying to turn some range of colours into transparency info. If you already have alpha in the video then it would be better to just use that info directly if it is possible.

I’m out of date. I don’t even know what video formats/codecs support alpha channels anymore, what have you got in this regard? So sorry I can’t actually point you towards a solution that does it the way I’ve indicated would be better in theory.