What are these artefacts called ?

[AssassiNBG]

K I could really use some help please. :) Here's my problem:

http://www.myfilebin.com/userfiles/tvhell/artefacats.png

Denoisers only amplify it, especially removegrain. Could you tell me what's that called, and how would you suggest to clean it ?

BTW TMPGEnc's Noise Reduction works very good on it, but it wipes out a lot of detail (characters' faces).

[Revgen]

It looks blocky. Did you capture this from sattelite or digital cable? If so, then it may be MPEG2 artifacts which a you can use a deblocker for.

[Anonymouses]

It looks blocky. Did you capture this from sattelite or digital cable? If so, then it may be MPEG2 artifacts which a you can use a deblocker for.

It's not blocking looks more like posterization to me. Here's a screenshot with the contrast increased:

http://img127.imageshack.us/img127/3358/artefact24kt.png

[AssassiNBG]

Yeah, source is DVB-S. What deblocker would you recommend, Revgen ?

[foxyshadis]

A deblocker wouldn't help. You need something like Smart Smoother HQ, MSmooth, or FFT3D to get rid of those... My preferred method is chaining the first two, but you have to be careful if you have a lot of details in the source.

[AssassiNBG]

MSmooth(threshold=15, strength=3, chroma=true)
VD_SmartSmoothHiQ(7, 90, 254, "weighted")

Doesn't do much of a difference, and blurs the hell out of some spots in the clip. And there may be more which I haven't noticed. FFT3DGPU is what I tryed (faster for my 6600 GT) but it's causing some lines across the image with sigma=3 and bt=1. :\

Or maybe if you could suggest a nice sharpener. (I couldn't get LimitedSharpen to work - but I read it's pretty good).

[Didée]

Could someone try to explain the artefacting? Frankly, I can't see anything particular distracting in that pic ... probably better to see in motion.

[Revgen]

Could someone try to explain the artefacting? Frankly, I can't see anything particular distracting in that pic ... probably better to see in motion.

If you adjust the brightness or contrast on the monitor, you should see it better.

[Revgen]

I'd suggest using ffdshow's SPP deblocking.

Go into ffdshow and enable SPP, then enter

ffdshow("default")

into your .avs script.

[AssassiNBG]

OMFG dude! It looks awsome! Let's hope after compression with xvid it doesn't end up ugly.

[Chainmax]

I don't see anything either (what exactly does posterization mean, BTW?), but if it needs deblocking, I suggest Deblock() from DGDecode.dll which comes on neuron2's dgmpgdec package. It uses an AVC-like deblocking method and it works really good.

[AssassiNBG]

Thankz for the suggestion. I'll surely try that one too!

[Seed]

It looks like halo to me. Search for "halo" and "dehalo". There is a recent thread on halo removal.

[Anonymouses]

It looks like halo to me. Search for "halo" and "dehalo". There is a recent thread on halo removal.

In the original picture? I hope you're not basing that on the picture I posted because that I both upped the brightness and sharpened which is those halos you see.

[mg262]

what exactly does posterization mean, BTW?I don't know whether there's a technical definition, but in practice it means reduced colour depth -- typically 4 bits per channel.

[Anonymouses]

I don't see anything either (what exactly does posterization mean, BTW?)

http://www.michaeldvd.com.au/Articles/VideoArtefacts/VideoArtefactsPosterization.html

[Chainmax]

Thanks for the quick answers :).

[Didée]

Just to have said it - returning home, and everything is obvious at a glance. You won't believe how crappy the monitor is that I have to work with in the office ... :cry:

Indeed, SPP deblocking seems like a good candidate for these blotches. As could Deen/Edeen, or a SmartSmoother or variant therof, all with pretty low thresholds. Also, low thresholded temporal smoothing could be a good way.
Filters we have just enough for that. However, making educated suggestions based on one single screenshot is, well, ridiculous. Post a sample, or just try all available filters. ;)

Final encoding will be the next problem then, if you want to keep it absolutely clean. Possible that AVC is the better choice compared to ASP like XviD, but my experiences with encoding animated sources are close to zero. :)

[foxyshadis]

Thanks for suggesting SPP for this too, I've needed a way to deal with it that isn't as destructive as the ones I offered.

(I always just call it "splotching", it's really common in undithered gifs, but I guess that's not a very technical term.)

[Mug Funky]

i've found degrainmedian works quite well on random blocking in flat areas. it can give a little temporal smearing, but really hardly any at all unless you're abusing it's limity/limituv parms.

[Chainmax]

OMFG, ffdshow SPP deblocking removed almost all of the blocking in my Simpsons sample vob!!! Check it out:

Source:
http://img350.imageshack.us/img350/5686/source0dh.png (http://imageshack.us)

Filtered:
http://img219.imageshack.us/img219/402/filtered8lj.png (http://imageshack.us)

:eek: :eek: :eek: :eek: ........

[Revgen]

Looks good. :)

SPP is my defacto deblocker for cartoons/anime. I like to use Nic's deblocker for live-action because SPP tends to smooth away too much detail.

@AssassiNBG

How did your Xvid encode turn out?

[mg262]

Chainmax,

It seems to have reduced the halos too (look at the bottom of the curtain)... wasn't the only filter you applied? It is pretty impressive -- but I'd want to see the effect on a clip with a bit more detail (painted background) before going wild. [Actually, Revgen, I guess you've just said much the same thing!] In any case, it would be interesting to know what method it uses.

[DryFire]

Go into ffdshow and enable SPP, then enter

ffdshow("default")

into your .avs script.

For some reason that gives me:
Script error: there is no function named "ffdshow"

ffavisynth.dll is in my auto loading directory.

[Revgen]

What version are you using?

I could be wrong, but I believe that Bobor made a GCC build of ffdshow that didn't have ffavisynth working properly.

Try going to http://ffdshow.sourceforge.net/tikiwiki/tiki-index.php?page=Getting+ffdshow and download Milan's builds.

[Chainmax]

The complete filterchain I used is the following one:

DeDot()
TFM(d2v="X:\wherever\SimpTest.d2v",mode=6,PP=7,slow=2,mChroma=true,chroma=true)
TDecimate(mode=1)
FixChromaBleeding()
ffdshow("default")
DeGrainMedian(mode=4)
aWarpSharp(depth=16,cm=1)
Crop(12,0,700,476,align=true)
Lanczos4Resize(640,480)
DeHalo_Alpha(rx=2.5,ry=2.5)
LimitedSharpen(strength=250)

The reason I didn't just use SPP on the "After" picture is because I wanted you guys to see the results of the whole filterchain. Previously, I had to use BicubicResize and avoid LimitedSharpen because they greatly amplified the issue no matter how much smoothing/deblocking I applied. Anyway, if you really want to see the effects of SPP, open the two images in VDub and use the "4X Size" option: you'll see some awful artifacts on the source that simply disappeared now.
Like RevGen said, there is significant detail loss, but I can live with that. For less problematic sources (animated or not), I'd recommend Deblock() from the DGMPGDec package. I don't know how it compares to Nic's deblocking, but it's very good.

[AssassiNBG]

Well. xvid did a great job preserving detail. Looks awsome compared to what I was trying with at first. Also Nic's deblocking couldn't do much. I'll try Deblock() from DGMPGDec tomorrow after school.

[Chainmax]

I don't think it will do much good with this kind of blocking/posterization hybrid kind-of artifacting (it didn't in my Simpsons clip), but please try it and report back.

[Chainmax]

Revgen, do I have to enable postprocessing and SPP in both "Video decoder configuration" and "VFW codec configuration"?

[Revgen]

Only the "Video Decoder Configuration" needs to be used.

EDIT

If SPP is blurring the details too much you can tweak the "Processing Strength" parameter.

[DryFire]

Switching to one of Milan's builds fixed it.

Another interesting filter to play with.