Quantcast Weird chroma flicker, how to remove from VHS capture? - digitalFAQ Forum
  #1  
11-28-2018, 09:43 AM
koberulz koberulz is offline
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Original is a TS file, not sure how to cut a sample without re-encoding. But it's got this weird chroma flicker thing going on. Anything I can do?

-- merged --

So I had a thought, and ended up with this:
Code:
DirectShowSource("clip.ts")
A = last
B = A.Trim(1,0)
Z = MergeChroma(A,B,weight=0.5)
return Z
Which seems to work on the graphics at least, but it looks terrible during fast-moving portions of play. Not sure if there's a better solution though.

EDIT: Also in VDub there's all manner of repeating frames, skipped frames, etc. Sometimes I'll just press F2 and get a completely different frame. When holding the left arrow it often only goes back a handful of frames and then freezes, while the frame counter keeps decreasing. Not sure what's happening there.


Attached Files
File Type: mp4 chromaflicker.mp4 (818.4 KB, 8 downloads)
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  #2  
11-28-2018, 01:55 PM
sanlyn sanlyn is offline
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Frame skipping, scrolling problems:
- Using DirectShowSource with AVC video.
- Frame width is not mod-8. It confuses many decoders. It should be mod-8, or mod-4 at worst . It's only mod-2.
- Your sample is too short and has no motion. It's pretty much a still photo.

Not enough information about the source or capture methods to make detailed conclusions.
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  #3  
11-28-2018, 02:11 PM
koberulz koberulz is offline
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What should I be using, if not DSS?

It's a downloaded file. It is what it is, pretty much.
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  #4  
11-28-2018, 04:43 PM
sanlyn sanlyn is offline
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Quote:
Originally Posted by koberulz View Post
What should I be using, if not DSS?
FFMS2 http://avisynth.nl/index.php/FFmpegSource
or
LSMASH Works http://avisynth.nl/index.php/LSMASHSource

DSS has been "retired" for 5 years now and is considered frame accurate for way video is encoded these days. The FFMS2 functions seem to be the favorites but geeks (who always have to be different) seem to like LSMASH functions.

Why the color is screwed up is another story. I have no answer for that one. Ask the maker what the hell was done to it (although it's probably too late at this point to do anything about it).
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  #5  
11-28-2018, 11:09 PM
koberulz koberulz is offline
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Weirdly the error only seems to affect the graphics. So I guess I could use the chroma merge and mask it...that sounds like a whole lot of fun.

Or just merge the chroma and roll with it. A one-frame 50% chroma desync is certainly the less distracting of the two errors.

Is there a way I can cut a sample of the original TS file, without having to re-encode?
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  #6  
11-28-2018, 11:45 PM
sanlyn sanlyn is offline
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I use TMPGEnc Smart Renderer and VideoRedo TV Suite to smart-render .ts and other h.264b cuts. Both have trial versions. There are (barely) a couple of freebies around but they're difficult to learn and don't smart render as cleanly as the first two mentioned. I deal with a lot of recorded HD and mp4 HD and SD downloads and couldn't live without TMPGenc and VideoReDo. TMPGenc has an easier interface, VideoReDo has a GUI that can be a little difficult. Users swear by the high quality output of both apps. I believe TMPGenc handles a greater variety of formats.
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  #7  
11-29-2018, 01:03 AM
koberulz koberulz is offline
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I guess a Premiere re-encode will have to do then. Shouldn't really matter for this though.

For the record I'm with the geeks, FFMS2 failed to rectify the issue I was having with DSS, LSMASH solved the problem.


Attached Files
File Type: mp4 flicker2.mp4 (12.17 MB, 1 downloads)
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  #8  
11-29-2018, 04:39 AM
sanlyn sanlyn is offline
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Yep, it's nutty. With me, sometimes it's the other way around, sometimes not. No one has figured out why.
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  #9  
11-29-2018, 05:14 AM
koberulz koberulz is offline
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Any thoughts on the flickering? My script definitely looks better than the original, but it's not an ideal solution by any means.
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  #10  
11-30-2018, 12:55 AM
sanlyn sanlyn is offline
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No idea what else to do with it. But it's a case of bad deinterlacing, definitely not with yadif or QTGMC. Also evident in aliasing and line twitter in diagonal lines on the court. It's also possible that the banner was broadcast that way.
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  #11  
12-04-2018, 08:09 AM
koberulz koberulz is offline
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Zero chance it was broadcast like that.

I'll probably go for the chroma merge (which gets the original broadcast colours) and mask, I guess. It doesn't look terrible on non-graphic areas, so I shouldn't need to go frame-by-frame or anything, just a couple of general-area feathered masks should get it done.

The whole archive really is a mess. There's 16:9 footage resized down to 4:3 then pillarboxed, 4:3 footage stretched out to 16:9, audio sync drift upwards of 30 seconds, 720x576 square-pixel footage...it's a disaster.

-- merged --

Weird thing is it seems to be confined to the yellow area as well, it's not even just a problem with the graphics.
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  #12  
12-04-2018, 08:33 AM
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lordsmurf lordsmurf is offline
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No, this can't be fixed without restoration, which means re-encoding. I doubt even hardware TBCs could remove that level of chroma damage.

For something like that, VirtualDub CCD.
Or Avisynth with KNLmeansCL() and followed up by CCD.

You must be careful with chroma fixes, as it easily making "mouse trails", ghosty noise.

I never use Avisynth with compressed video, and always first extract out to lossless using VirtualDub2. For quick testing, ffvideosource (ie ffms2)

With codec choices, be careful of mod2/4/6/8 as sanlyn notes. mod8 means divisible evenly by 8, not a fractional dividend.

Sometimes errors like this are in the source, before the tape recording. Never assume errors are your fault, verify. It means you've fixing embedded issues, and hardware will be lesser effective or not effective at all. Software is the only solution.

I also use TMPG SR fir cutting H264. Probably the only app that doesn't screw up, re-encodes GOP instead of I-frame cutting only. That's ideal.

A Premiere re-encode? Premiere is best as editor, and final output only.

I didn't very look at the interlace, focusing on chroma only. If sanlyn says it's a mess, it probably is.

You have a lot of problem source, but it's good to see you trying to repair it as much as possible.

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  #13  
12-04-2018, 12:35 PM
koberulz koberulz is offline
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Quote:
Originally Posted by lordsmurf View Post
No, this can't be fixed without restoration, which means re-encoding. I doubt even hardware TBCs could remove that level of chroma damage.

I also use TMPG SR fir cutting H264. Probably the only app that doesn't screw up, re-encodes GOP instead of I-frame cutting only. That's ideal.

A Premiere re-encode? Premiere is best as editor, and final output only.
Regarding these matters, I was just talking about the best way to post a sample here. All you really need to see is what the chroma is doing.

This also isn't a VHS capture. It's a file from the internet, the original source of which was presumably some sort of professional format, which may or may not have been tape.

Quote:
For something like that, VirtualDub CCD.
Or Avisynth with KNLmeansCL() and followed up by CCD.

You must be careful with chroma fixes, as it easily making "mouse trails", ghosty noise.
The issue is it's really bad on the yellow/orange areas of the graphics, and absolutely nonexistent elsewhere. I'm already well over halfway through matting a MergeChroma version with the original, so I'll just stick with that. I don't have KNLmeansCL(), and CCD does absolutely nothing.
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  #14  
12-05-2018, 03:06 AM
koberulz koberulz is offline
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Incidentally I resized it to 1024x576 and then lopped off 152 pixels from each side, to remove the pillarboxing. But this also removed a bunch of the content because it was actually 766 pixels wide instead of 720. FFS.
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