It’s actually a part of the source video, which is ripped losslessly from the DVD:
I guess they screwed up encoding it for the disc. It probably wasn’t so bad on old TVs.
I fell in love with the Theia model and and turning sharpen all the way to 100, but then I noticed it made this problem much worse. Sharpening an error makes a big, ugly error, obviously. Using Artemis LQ softens the problem a lot, but it doesn’t add nearly as much sharpening/detail.
I thought maybe I could run Artemis LQ to reduce the problem and then Theia to add detail without wrecking it too much, but running Theia after the video has already been processed by Artemis doesn’t seem to have any noticeable effect on anything.
What is this problem called? An artifact? A flicker? Is there anything else I can try, or is Artemis LQ as good as it’s going to get?