Sorry, to resurrect this thread, @grahamh but I said before:
I spotted this post in another thread:
This command fixes the problem I was talking about in the post I just quoted, and makes things as sharp as they used to be a couple of months ago, instead of more shimmery. Unfortunately the command also disables the newly-enabled diagonal filtering that looks so nice on hardware-decoded field-interlaced DVD remuxes.
It’s possible that’s not a coincidence, and that turning on diagonal filtering makes cases where the deinterlacer goes into field-interlaced mode when it shouldn’t look worse than they used to. It’s also possible that there’s some other additional post-processing being enabled as well, and both that and the diagonal filtering are deactivated by that command. But whatever is happening, there’s a definite association between those two things.
I don’t know if the issue kallek was complaining about in the other thread is the same thing I was grumbling about. Maybe! 