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View Full Version : Horizontal lines on progressive source

martinfrombern
17th September 2009, 22:57
I've seen this kind of artifact before and always wanted to know what is it and what's causing it. Looks like some kind of interlace artifact, but that confuses me because source is progressive.
Seems that Vinverse() deals very good with removing it. Is that the right approach or is there a better one?

screenshot (thumbnail)
http://thumbnails22.imagebam.com/4919/6a2aa449185571.gif (http://www.imagebam.com/image/6a2aa449185571)
Guest
17th September 2009, 23:29
Not seeing any lines here. Can you point them out?
Lyris
18th September 2009, 04:21
Do you mean the very small scanlike-like pattern visible above the left eye?

This is the result of Interlaced encoding. The two fields are compressed separately, so basically you'll see compression artefacts with scanlines "running through" them.

It is very common for 50hz film material to be encoded interlaced, even if the source is progressive. Most PAL DVDs are done this way :(
Inspector.Gadget
18th September 2009, 04:28
Post a representative source sample. Open the VOBs with DGIndex, set your cut points using the bracket buttons, and then "Save Project and demux video." Delete the d2v file, upload the m2v to mediafire, and post the link here. That way we can all see what you're talking about it.
martinfrombern
18th September 2009, 08:25
Do you mean the very small scanlike-like pattern visible above the left eye?
exactly. they are all very small and are all over the place. i updated screenshot with pointers to just few of them.
so the reason seems to be interlaced encoding. what's to correct way to deal with it? It's looking ugly to me, and I'm sure it's note very compressable :)
Lyris
18th September 2009, 21:09
I don't think there's a lot you can do with that, unfortunately. Maybe if you try vertically softening the image, you can blur out the scanline artefacts without impacting on actual picture detail (depending on how detailed the source is).

Another strategy would be to do light temporal denoising on the whole clip then re-grain it afterwards. Not an especially tactful method, but it would likely kill the artefacts. (And probably make some new ones...)