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)

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

Quote:

Originally Posted by Lyris

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...)

17th September 2009, 22:57	#1 \| Link
martinfrombern Registered User Join Date: Mar 2009 Posts: 57	Horizontal lines on progressive source 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)

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17th September 2009, 23:29	#2 \| Link
Guest Guest Join Date: Jan 2002 Posts: 21,901	Not seeing any lines here. Can you point them out?

18th September 2009, 04:21	#3 \| Link
Lyris Registered User Join Date: Sep 2007 Location: Europe Posts: 602	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

18th September 2009, 04:28	#4 \| Link
Inspector.Gadget Registered User Join Date: May 2008 Posts: 1,618	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.

18th September 2009, 21:09	#6 \| Link
Lyris Registered User Join Date: Sep 2007 Location: Europe Posts: 602	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...)