Chroma Upsampling (Chroma Interpolation)

Shooting green-screen onto a 4:2:0 chroma-subsampled format, intending of course to use it for chroma-keying.  Obvious disadvantage is green-ness of green-screen only gets sampled at quarter-resolution.  Not a show-stopper, given my target deliverable is standard definition, but anyhow, towards perfectionism, is there any way to up-sample to 4:4:4 i.e. full definition colour? It does occur […]