[Michael Lansdell]"I mostly work with SD Pal programmes. I've often wondered about the filters 'Color Smoothing - 4:2:2' and 'Color Smoothing - 4:1:1'. What are these for?"
Chroma Smoothing helps to rebuild the Chroma after Downsampling.
That one works when you edit 411 stuff (DV NTSC, DVCProPAl) on a 422/444 sequence.
For 420 stuff the only Chroma smooth filter I know is the Nattress.