Quantcast Flickering colours on VHS tape? - digitalFAQ Forum
  #1  
10-04-2016, 01:07 AM
koberulz koberulz is offline
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Is there anything I can do to fix the flickering going on in this clip?


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File Type: avi Flickering.avi (22.86 MB, 51 downloads)
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  #2  
10-04-2016, 09:58 AM
msgohan msgohan is offline
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An unprocessed sample would be better. This one was converted to RGB at some stage, so the true chroma channels can't be examined.

My thinking would be that heavy temporal noise reduction on the chroma should even out the flickering more, but if it does work you'd have to live with the chroma trailing artifacts that result.
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10-04-2016, 11:10 AM
koberulz koberulz is offline
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Attached the unprocessed version.


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File Type: avi Unprocessed.avi (37.54 MB, 40 downloads)
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  #4  
10-04-2016, 12:05 PM
msgohan msgohan is offline
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I could be wrong, but it looks like this one went through an RGB intermediate stage too. If you don't mind, please briefly list the workflow used to create this file from VCR all the way to final AVI. Or if it's too much trouble, hopefully someone else has some ideas.
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  #5  
10-04-2016, 12:18 PM
koberulz koberulz is offline
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The tape was inserted into a Panasonic NV-HS1000.
The video signal then passed through an S-Video cable to a TBC-1000.
Then through another S-Video cable to a Hauppauge USB-Live2.
Into a PC, where it was captured as a YUY2 Lagarith AVI file in VirtualDub.

What do you mean it looks like it went through an RGB intermediate stage?

I threw VirtualDub's default temporal smoother at it, and it definitely improves things if I crank it up enough. Not sure what 'chroma trailing artefacts' are, so I'm not sure at what point it starts to look bad (I can only play it at one or two frames per second, too, which doesn't help). There is a point at which the outline of the Mitsubishi logo starts showing through the channel 7 logo before the cut, so I've kept it below that line, but other than that...
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  #6  
10-04-2016, 05:49 PM
sanlyn sanlyn is offline
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Quote:
Originally Posted by koberulz View Post
What do you mean it looks like it went through an RGB intermediate stage?

I threw VirtualDub's default temporal smoother at it
What msgohan means is that if you "threw" a VirtualDub filter at the it, it performed an RGB conversion (temporal smoother is an RGB filter. It won't work in YUY2). Then the vid was recompressed to YUY2 (?). But that doesn't undo the action of the RGB conversion.

This looks like a multigenerational tape. Whether it is or not, the tape has been abused and/or improperly stored in heated, humid conditions. The "flicker" (which is not really what it is) is a sign that the oxide layer is separating from the adhesive that holds it onto the mylar. The flood of rips and dropouts are one sign of that damage. This could be improper storage or it could be tape that was damaged during play -- literally, it isn't making solid contact against the video heads. I've seen this so many times it's deja vu from so many old damaged family tapes.

You can throw filters at it forever without getting very far, or throw filters at it until you don't have much video loft to watch. You can only do the best you can with temporal smoothers which don't work so well with interlaced video, so use smoothers designed for interlaced source. If you use strong temporal smoothers later in the video when there is motion, you'll soon learn what "chroma trailing artifacts" look like.

Some shortcomings are evident in the capture stage. Colors are clipped above y=16 and the original is seriously over saturated.

Sometimes a video is so badly damaged you just have to do the best you can and live with it. We've all been there. I made a trial run by deinterlacing, shifting chroma around, applying motion smoothers, etc., and reinterlacing. But later parts of the video are bound to suffer from so much filtering. Avisynth and the captured colorspace were required for the attached mp4. Others could get different results and use different methods,


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File Type: mp4 TrialRun2.mp4 (2.61 MB, 21 downloads)

Last edited by sanlyn; 10-04-2016 at 06:36 PM.
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  #7  
10-04-2016, 07:21 PM
msgohan msgohan is offline
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Quote:
Originally Posted by koberulz View Post
What do you mean it looks like it went through an RGB intermediate stage?
Chroma edges as sharp as what's found in your video are impossible with any consumer analog tape format. They are also probably (definitely?) impossible to send along an S-Video wire even from an ultra-high quality source. Typically these false edges are produced as artifacts from a YUY2 -> RGB -> YUY2 roundtrip, because each conversion step is never perfect.

YUY2 source, UtoY():
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ConvertToRGB().ConvertToYUY2().UtoY()
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Unprocessed.avi, UtoY()
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Maybe instead caused by cranking up sharpness on the Hauppauge proc amp settings? Dunno. But it's somewhere on the digital side of things, not the analog side.


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  #8  
10-04-2016, 08:35 PM
sanlyn sanlyn is offline
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msgohan: some good insight into facets of RGB conversions I've not considered.

How the original sample came to be so saturated or sharpened I can't know. But I doubt the player is doing it on its own. Half the noise level faded when I lowered saturation about 40%. I know that some users pump saturation and.or sharpness to compensate for old and faded tape, but it's usually overdone.

But I'm just guessing. Perhaps koberulz can give more info about this tape's history.
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  #9  
10-04-2016, 11:47 PM
koberulz koberulz is offline
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Quote:
Originally Posted by sanlyn View Post
What msgohan means is that if you "threw" a VirtualDub filter at the it, it performed an RGB conversion (temporal smoother is an RGB filter. It won't work in YUY2). Then the vid was recompressed to YUY2 (?). But that doesn't undo the action of the RGB conversion.
I knew that, I was asking how it could look that way.

Quote:
You can only do the best you can with temporal smoothers which don't work so well with interlaced video, so use smoothers designed for interlaced source.
Suggestions?

Quote:
Colors are clipped above y=16 and the original is seriously over saturated.
What does this mean?

Quote:
Sometimes a video is so badly damaged you just have to do the best you can and live with it.
Trust me, I know I'm not getting this one to look great. I'm largely after 'less distracting'.

Quote:
Maybe instead caused by cranking up sharpness on the Hauppauge proc amp settings? Dunno. But it's somewhere on the digital side of things, not the analog side.
I always leave sharpness at default in the proc amp; the only settings I've ever altered are brightness and contrast. The Panasonic has a sharp<>soft slider on the front of the machine, could that be it?

The tape isn't mine, and in fact has existed longer than I have, so I can't help you with its history.
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  #10  
10-05-2016, 12:50 AM
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lordsmurf lordsmurf is offline
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The original "flickering" looked like chroma noise from reusing a tape, where the recorder lacked flying erase heads.

The next "unprocessed", however, show it to be just plain chroma noise. Nothing special, nothing to do with reuse.

This is why it's important to always give unprocessed video, when showing samples. Sometimes attempts to fix it can muddy the situation. And in this case, make repair harder.

- The 1st issue would have been hard, while the 2nd really is not.
- The 1st issue is repaired best by temporal chroma NR in Avisynth and/or VirtualDub, while the 2nd is best fixed with VirtualDub CCD.

There's also a lot of chroma offset, and Avisynth is needed for that. (Best method, at least. CCD can somewhat hide it, but not entirely.)

Color being clipped or not clipped is probably the source or the tape, not the conversion method. Or both. Or all of the above. VHS is crummy. It can be made better, of course. But I use my eyes, not meters and graphs. In this short sample, I'm not willing to adjust colors. It's fine.

I don't have an issue with the chroma edges. I don't see halos.

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  #11  
10-05-2016, 01:05 AM
koberulz koberulz is offline
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So what am I doing that's making it worse? I've already got CCD in the VirtualDub chain that produced the first sample. It definitely looks worse than with VDub's default temporal smoother added (which gets me in the ballpark of sanlyn's sample).

I've used flaXen's VHS filter in VirtualDub to handle the chroma shift. What's the reason for preferring AviSynth?
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  #12  
10-05-2016, 01:09 AM
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Not sure.

I can't open your files in VirtualDub. Is that Lagarith, and not Huffyuv? On my current video system, to appease the codec gods, I've not installed anything that I don't use. I'd need a Huffyuv conversion.

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  #13  
10-05-2016, 01:35 AM
koberulz koberulz is offline
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I can't open HuffYUV in Premiere, so I always use Lagarith.


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File Type: avi FlickeringHuff.avi (31.42 MB, 1 downloads)
File Type: avi UnprocessedHuff.avi (37.48 MB, 3 downloads)
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  #14  
10-05-2016, 02:22 AM
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I have no issues with Premiere. The fix to install both x86 and x64 together was discussed in another thread.
See here: Problems encoding with MainConcept TotalCode Studio?

This was an easy problem.

See attached. I could have tweaked it more, but this is mostly just proof of concept.
- Avisynth offset fix (Flaxen is lousy)
- Avisynth CNR
- VirtualDub CCD
- VirtualDub Chroma NR
- VirtualDub CCD again

I also added a stabmod() and my script to remove most tracking/dropout issues. This last one is a bit hard to explain, not ready to do it yet. Even on Skylake CPU, these drag it down to 4fps, so not for weak systems!

See clip attached. MP4 @ 15mbps, AVI not needed, huge.

You're right, CCD was not enough. So it may still be an erase head issue.


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File Type: mp4 unproc4_out.mp4 (9.79 MB, 26 downloads)

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  #15  
10-05-2016, 03:38 AM
koberulz koberulz is offline
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Quote:
Originally Posted by lordsmurf View Post
I have no issues with Premiere. The fix to install both x86 and x64 together was discussed in another thread.
See here: Problems encoding with MainConcept TotalCode Studio?
Not really sure I follow that. Is there any reason to go with HuffYUV over Lagarith?

Quote:
- Avisynth offset fix (Flaxen is lousy)
- Avisynth CNR
- VirtualDub CCD
- VirtualDub Chroma NR
- VirtualDub CCD again
What's the actual code in AviSynth to use those? I assume 'CNR' and 'Chroma NR' are both short for 'chroma noise reduction'?

What are you achieving by running CCD either side of Chroma NR in VDub?

What's lousy about Flaxen?

Quote:
I also added a stabmod() and my script to remove most tracking/dropout issues.
What does stabmod do? I Googled it and found your AviSynth guide thread in the General Discussion section, but there doesn't seem to be much info on what it actually does.
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  #16  
10-05-2016, 05:35 AM
msgohan msgohan is offline
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Very nice work LS, but the chroma does trail into the shot change over 4 frames before disappearing on the 5th. We need a sample from koberulez with real motion to see how much artifact balancing is truly required.

Quote:
Originally Posted by koberulz View Post
The Panasonic has a sharp<>soft slider on the front of the machine, could that be it?
No. As I mentioned, it's happening after the analog signal has entered the digital domain: at the Hauppauge digitization step or thereafter -- leaning heavily towards "thereafter", especially now that you've confirmed Hauppauge sharpness and saturation were at default. Even if something like the TBC-1000 was converting to RGB internally, or you cranked sharpness to insane levels with 10 video processors chained together, the chroma edges would still end up softened before and/or at the capture stage because of the limitations of S-Video and capture device samplers.

I don't know whether this makes things any more clear, but the first test pattern in each "VHPatterns2" column in this thread includes a patch for checking chroma resolution (on the bottom, particularly the one labelled "1.5"). If you look at the greyscale chroma view, you can see how blurry even the best capture devices that I've used are, as compared with the super-sharp chroma edges found on your capture. (I discovered that the DVD player I used is partly at fault for reducing the chroma res, but that's another story: most of the capture devices can't even keep up with the reduced level put out by this player, and DVD has much higher chroma bandwidth than VHS. VHS captures "should" always have blurry chroma.)

Quote:
Originally Posted by lordsmurf View Post
I don't have an issue with the chroma edges. I don't see halos.
There are luma halos. Most visible along the "P" in "Perth", I think.

These added chroma edges from roundtrip conversion are invisible when actually watching content. The only reason I brought it up was because the added conversions hinder analysis and possibly processing. Had you guys responded with filtering suggestions first I'd have kept my mouth shut and left it to the restoration experts.
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  #17  
10-05-2016, 06:01 AM
sanlyn sanlyn is offline
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Quote:
Originally Posted by msgohan View Post
These added chroma edges from roundtrip conversion are invisible when actually watching content. The only reason I brought it up was because the added conversions hinder analysis and possibly processing. Had you guys responded with filtering suggestions first I'd have kept my mouth shut and left it to the restoration experts.
Thanks for the links to that chroma testing. If you're curious about the mp4 I posted it was done entirely in YUV, mostly with a few passes of dfttest and FluxSmoothT -- not that I'm happy with the results. I treated it as both progressive and as interlaced and got exactly the same results, as it seemed originally telecined and incorrectly deinterlaced, then the VCR played it as interlace while mediaInfo sez progressive.

That video has certainly been around a few neighborhoods, at least one of which was digital, and looks as if it went from tape to digital and back to tape, then maybe sat in the sun on someone's window sill or in an auto's trunk for a few summers. I echo the requests, what else is on this tape? Is it a TV show? Are there people, animals, cars, motion, what?
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10-05-2016, 06:04 AM
koberulz koberulz is offline
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Not sure how helpful a motion sample will be; quality is all over the place between the opening graphics package, the in-studio introduction, and then even each individual camera angle through the game. I was fiddling with the chroma shift earlier to get the Mitsubishi logo right, and now it's completely out of whack during the main program.

So this one's a serious case of multiple combined restoration efforts being required, and as such posting a clip from the game itself probably isn't helpful with resolving a graphics issue. All the motion there, and the general lack of any graphics at all, should mask the chroma noise a bit anyway meaning lower settings can be got away with in order to preserve everything else.

In any event, I can't put together samples right at this moment.

EDIT: sanlyn posted while I was typing. It's a basketball game from 1985.
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  #19  
10-05-2016, 06:07 AM
msgohan msgohan is offline
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Quote:
Originally Posted by sanlyn View Post
If you're curious about the mp4 I posted
To be honest I didn't check it out until now, but it looks like a nice result as well. Since the sample doesn't really feature motion I wasn't too interested in checking out the restorations. I only bothered downloading Smurf's because he mentioned fixing tracking/dropouts. (I really am that lazy.)
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10-05-2016, 06:08 AM
koberulz koberulz is offline
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lordsmurf, I'm trying to download your AviSynth filters pack from the guide thread, but it's failed twice. Is there an issue with it, or is the problem at my end?
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