Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
[Help] HDTV jagged "step" artifacts
#1
I hinted at this in another thread, thinking it was due to interlacing in the footage. After looking at the normal interlaced footage, I think I can somewhat safely exclude this possibility.

Maybe it's more like some kind of aliasing.

Here's a comparison screenshot. Left is the HDTV, right is a WEB-DL (including some DeHaloing):

    (Click to enlarge)

You can see how the lines of the font are clear on the right, but "jagged" on the left. 

Any idea what might be causing this and what a good solution would be, if there is any? I'm already combining the two sources, which mildens the effect, but it's still visible.

I get the same problem with finer textures in a few shots, like finer lining on a shirt, resulting in a form of aliasing, whereas the image is rather clear in the WEB-DL.

I doubt it's simple blocking, as it is too ... predictable and constant for it, and the bitrate of the source is also acceptable, in fact it's a bit better than the WEB-DL (although MPEG-2)
Reply
Thanks given by:
#2
Dunno... maybe oversharpening (where WEB-DL seems a bit too blurred IMHO), combined with MPEG-2 macroblocking; consider that MPEG-2 to get the same quality of AVC should have a considerable higher bitrate. Take a look at the advanced Kush Gauge calculator to see if the quality if "right" (educated guess, but still better than nothing): http://blog.sporv.com/advanced-kush-gauge-calculator/
Reply
Thanks given by:
#3
The blurriness is from the Dehaloing, which didn't work out as ideally as I hoped whenever there's text in the image.

And I think the jaggedness might be from bad upscaling and aliasing in the original source, exaggerated and blurred through the bad upscale, as someone on Blutopia suggested. Upscaling a text in Photoshop with Bilinear gives similar artifacts. Makes me wonder if I can use Debilinear to reverse the effect. I tried as much to 1280x720, but it wasn't ideal. I would need to somehow determine the native resolution I think. No idea how I would do that tho.

Your calculator spat out 13522 kbps. Video has 17.2 Mbps. Though it's 29.97, I used 23.976 tho. Your calculator says 16903 kbps for 29.976. But it's not "real" 29.976, so I dunno.

For H264 your calculator says 6960 kbps. WEB-DL has 9864 kbps.

So according to that data they should be both fine. I think they did some weird processing with the source, that's why it looks shite.
Reply
Thanks given by:
#4
Well, if it's "only" bad upscaling, the jagginess should be even in the whole text, but it seems it is really noticeable in just few places - like on the bottom right of the R, and on all left side of the A. Of course, it could concur to other factor; even if bitrate is quite good, it is still quite low to allow macroblocking in MPEG-2.

Have you tried deblock_qed? Maybe it can help somehow; in addition, I'd try a denoiser, too. Still, merging the HDTV with WEB-DL (after some tweaks on the former) is maybe the best solution.
Reply
Thanks given by:
#5
Could you send me the DCTFilter files? They seem offline everywhere and are required for DeBlock_QED

Also, how the hell does MaskTools not support YV24, when it clearly claims to ... pos.
Reply
Thanks given by:
#6
DCTfilter.dll: http://www53.zippyshare.com/v/Mxjvo2no/file.html
Reply
Thanks given by:
#7
Thanks! Doesn't seem to do much at all.

Edit: just realized this might sound sarcastic because I wrote the statements together. It was a real thanks tho.
Reply
Thanks given by:
#8
You know, an avisynth script is like a food recipe: any ingredient could make a small, or huge, difference, but the grandtotal of them makes the final result... so, ***maybe*** using it with another filter ***could*** help... or not, who knows? Big Grin you should only test. Doom9 forum is a great resource for avisynth, so let's try to find info there, or start a new thread; I found some important help there!
Reply
Thanks given by:
#9
I found 2 more WEB-DLs of this older master. They all have exactly the same issue. So I suspect it's ultimately down to the master, as those are neither interlaced nor have identical blocking. I'm trying a Median to at least reduce compression artifacts, which works, but it also loses detail, as the WEB-DLs seem to have been degrained and have low-ish bitrates. Sad. Sad

Yeah I know, playing around is always good, but you need some kind of intuition, which I currently lack. No biggie though, the project is already pre-rendered with the combined HDTV and WEB-DL. Now I just need to go through it and find the instances where AutoAlign fucked up, fix it, and v1.0 should be as good as good to go. Big Grin
Reply
Thanks given by:
#10
Hint: sharpen the most blurred sources - limitedsharpenfaster works best IMHO - then, when median'ed, the eventual oversharpening of this script (very light, if any), should disappear! Of course, play with the settings - I usually only tweak the strenght, though.
Reply
Thanks given by:


Forum Jump:


Users browsing this thread: 1 Guest(s)