Corner shadow artifacts

[introspect]

Hi, all. I'm seeing artifacts appear in the vicinity of slight shadowing. I have a couple frames taken post-IVTC, but these corner artifacts were present in the source as well.

http://img523.imageshack.us/img523/6062/corners1mu5.th.jpg (http://img523.imageshack.us/my.php?image=corners1mu5.jpg)http://img523.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

http://img372.imageshack.us/img372/5958/corners2sm0.th.jpg (http://img372.imageshack.us/my.php?image=corners2sm0.jpg)http://img372.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

What do you think it is/what's causing it? What do you recommend to remove them, if they should be removed?

[pitch.fr]

it's called vignetting I think :
http://www.google.com/search?hl=en&q=vignetting&lr=

how it ended up on some music video....no clue :D

I think a friend of mine is using some AVS filter to fix the problem on his DIY pj, I can ask him if you like

[introspect]

Ah, makes sense. I guess the vignetting part was deliberate. But as for the artifacts introduced by it, what would you call them? I don't have a lot of experience in identifying these things, but from my limited vocabulary it may be rainbowing or ringing, and there seems to be filters/scripts dedicated to addressing either, but not both? Or it could be something completely different and I don't know the term.

[Sagekilla]

The darker parts could be considered "flat" so the encoder that this was source from might have allocated less bits than it needed, so you get blocking.

That's what happened in x264 before AQ, anyway.

[Mug Funky]

ugh. ugly. vignettes are so cheesy. they're like the new lens-flare-plugin effect. too bad they don't improve crap pictures at all. with a much softer edge and the correct aspect ratio it might be acceptable.

sry, me being a snobbish grader.