VHS Chrome noise - Postprocessing

[solouplay]

https://www.pixeltopic.com/image/yavskvbvtqkqvad/?size=full
The footage is from 1986, it's not a master-copy, but probably 3rd gen or something like that.

As you can see there's bad chroma noise/bleeding happening in the picture. And I was wondering if there's any filter for VirtualDub that can reduce this effect?
I tried the "field shift" plugin with virtualdub, it does help since I can move the chroma to line up properly, but you still get the blue/purple shaders.

Also, can somebody explain why this is happening? I'm thinking that the color-burst signal on the VHS-tape is damaged so the colors in detailed areas are getting distorted?

Help very much appriciated! :)
/Solouplay

Edit: I messed up the title...

[jagabo]

I think you problem is the incorrect handling of interlaced YV12 video in VirtualDub, bad deinterlacing, and oversharpening, not a chroma shift/bleed issue. Upload a sample of your original video, not reencoded.

[solouplay]

I think you problem is the incorrect handling of interlaced YV12 video in VirtualDub, bad deinterlacing, and oversharpening, not a chroma shift/bleed issue. Upload a sample of your original video, not reencoded.

No I doubt it. Here's a picture of the absolute raw capture (no de-interlacing)
https://www.pixeltopic.com/files/2017/2/uxweacoyiluceu.png

I have captured many tapes with the same settings, but this is the only tape that has this kind of problem, so I don't think it's a capture/digital problem :)
/Solouplay

[jagabo]

suit yourself

[solouplay]

suit yourself

What do you mean? :)

[jagabo]

I'm not going to bother looking at the problem without a video sample.

[solouplay]

I'm not going to bother looking at the problem without a video sample.

I'm so sorry, I thought you said (picture) sample :)
https://www.youtube.com/watch?v=-dFdl0viHro&feature=youtu.be

That's a sample from the raw capture, not de-interlaced or anything. 720x576 at 25fps
PS: When I'm capturing I'm using YUV420, and later I de-interlace with Yadif (double fps)

Edit: It seems like youtube have de-interlaced the sample, I don't know if that's a problem? :/

[jagabo]

Youtube reencodes, screwing up everything. Upload a sample directly to this site. Use the "Upload files/Manage attachments" button below the edit boxes were you enter your posts.

[solouplay]

Ok, here it is

[TimA-C]

You're sure the visor hasn't got a graduated tint on it?

[solouplay]

You're sure the visor hasn't got a graduated tint on it?

The chroma problem is present all the time, not only during the scene I've shared :)
The quality of this tape is bad overall, it's probably a 3rd or 4th generation copy and it has been stored in uncertain conditions for 30 years.

[jagabo]

You've encoded interlaced video with an h.264 encoder in progressive mode. That has caused the two fields of the chroma channels to blur together. There's also a lot of chroma carrier crosstalk in the luma channel causing herringbone noise. Those are things you should fix the next time you capture, but not the main issue you're asking about here.

There's something definitely wrong with the U channel. It has severe halos at many edges:


[Attachment 40758 - Click to enlarge]

That's the original color frame at the top left (simple bob deinterlace), just the luma channel at the top right, the U channel at the bottom left, and the V channel at the bottom right. You can see the crosstalk in the luma channel. And the V channel looks about normal for VHS (ie, not sharp). But I don't know how those halos got in the U channel. Dehalo_alpha() on the U channel might help.

[jagabo]

Here's a dirty trick, invert and copy the V channel to the U channel:

YtoUV(VtoY().Invert(), VtoY(), last)


[Attachment 40759 - Click to enlarge]

The chroma could be sharpened a bit too.

[solouplay]

You've encoded interlaced video with an h.264 encoder in progressive mode. That has caused the two fields of the chroma channels to blur together. There's also a lot of chroma carrier crosstalk in the luma channel causing herringbone noise. Those are things you should fix the next time you capture, but not the main issue you're asking about here.

Oh, I've always thought that it was the VCR causing those issues, and fixed it in post-processing.. Thanks for letting me know! :)

Here's a dirty trick, invert and copy the V channel to the U channel:
YtoUV(VtoY().Invert(), VtoY(), last)
The chroma could be sharpened a bit too.

That looks great! Very good work!
But is this a script meant for AviSynth? I'm using VirtualDub, but I'll see if I can find a solution.
Also I can't seem to find any chroma sharpening filters, maybe I need to use a script for that too.

Thanks for helping me out! :)
/Solouplay

[pandy]

You can try to apply "erode" over U channel - it looks like some analog sharpen filter was applied to U signal and as such this nasty "halo".

[jagabo]

You've encoded interlaced video with an h.264 encoder in progressive mode. That has caused the two fields of the chroma channels to blur together. There's also a lot of chroma carrier crosstalk in the luma channel causing herringbone noise. Those are things you should fix the next time you capture, but not the main issue you're asking about here.

Oh, I've always thought that it was the VCR causing those issues, and fixed it in post-processing.. Thanks for letting me know!

The blended chroma can't really be fixed in post. The crosstalk can be reduced with a capture device with a better comb filter.

Here's a dirty trick, invert and copy the V channel to the U channel:
YtoUV(VtoY().Invert(), VtoY(), last)
The chroma could be sharpened a bit too.

That looks great! Very good work!

But it's not a general fix. It works for this shot because the U and V channels are largely complimentary. With other colors it may cause big color shifts.

But is this a script meant for AviSynth? I'm using VirtualDub, but I'll see if I can find a solution.

Yes, it's an AviSynth command.

Also I can't seem to find any chroma sharpening filters, maybe I need to use a script for that too.

In AviSynth you would do something like

SeparateFields()
MergeChroma(last,  aWarpSharp(depth=20)
Weave()

or even better:

SeparateFields()
MergeChroma(last, Spline36Resize(width/3,height).aWarpSharp(depth=20).Sharpen(0.5,0.0).Spline36Resize(width,height))
Weave()

The reason for downscaling the width before sharpening is because VHS has much less chroma resolution horizontally than vertically. This way the colors are sharpened more equally vertically and horizontally.

[solouplay]

You can try to apply "erode" over U channel - it looks like some analog sharpen filter was applied to U signal and as such this nasty "halo".

Do you mean some kind of AVIscript?, I'll try everything;)

SeparateFields()
MergeChroma(last, Spline36Resize(width/3,height).aWarpSharp(depth=20).Sharpen(0.5,0.0).Spline36Resize(width,height))
Weave()

The reason for downscaling the width before sharpening is because VHS has much less chroma resolution horizontally than vertically. This way the colors are sharpened more equally vertically and horizontally.

I just got AVIsynth going, it's my first time using it.
I inserted the code listed above and it does seem to do something, but for some reason only the top left quarter of the screen is working, the other three quarters are green?
Is it thinking that my video is in 320x240 resolution? Do I have to specify 720x576 for some reason? :)

LoadPlugin("D:\Program\VirtualDub Avisynth\plugins\aWarpSharp.dll")
avisource("H:\Video\duc86_raw.avi")
SeparateFields()
YtoUV(VtoY().Invert(), VtoY(), last)
MergeChroma(last, Spline36Resize(width/3,height).aWarpSharp(depth=20).Sharpen(1,0.0).Spline36Resize(width,height))
Weave()

[jagabo]

I think your h.264 decoder is putting out YV24 instead of YV12. aWarpSharp doesn't work correctly with YV24. Add pixel_type="YV12" to AviSource line:

avisource("H:\Video\duc86_raw.avi", pixel_type="YV12")

If your video is the same as the sample you sent, it's 720x576, interlaced, top field first.

[jagabo]

Here's an example of what happens with YtoUV(VtoY().Invert(), VtoY(), last):


[Attachment 40770 - Click to enlarge]

On the left is the full range of colors, on the right the result of the transform. You can see that greens and purples have been lost, replaced with browns and blues.

[solouplay]

I think your h.264 decoder is putting out YV24 instead of YV12. aWarpSharp doesn't work correctly with YV24. Add pixel_type="YV12" to AviSource line:

Now it works! :)

Here's an example of what happens with YtoUV(VtoY().Invert(), VtoY(), last):
On the left is the full range of colors, on the right the result of the transform. You can see that greens and purples have been lost, replaced with browns and blues.

Okay, yeah that won't be good for moving images.

So now I got the sharpening filter to work. Is there any other filters you would recommend? :)

[solouplay]

Well at any rate it sure is getting better! Again, thanks for all the help! :)



/Solouplay