Thanks for your info. I haven't seen any banding in my conversions yet. I just like to add dithering for safety reasons when going down to 8bit because I have read that it is recommended when bit depth is reduced.

I would be interested to know if DGHDRtoSDR uses dithering when converting to YV12.

If not, I think this script should be fine when I need dithering to prevent banding:

ConvertBits(16)
DGHDRtoSDR(fulldepth=true)
ConvertBits(8, dither=0)