What VHS error is this?

[premiumcapture]

The chroma seems to glow around the sword, feel, and arms, and it seems to trail the action. Not sure what this called or how to tackle it.

Sample attached in Lagarith (166 MB).

[jagabo]

You mean the halos at high contrast edges? Those are from over sharpening by the VHS deck. And maybe from your capture device too. If your VHS deck has a sharpness control turn it down. The same goes for your capture device. You can alleviate it with a dehalo filter like dehalo_alpha() in AviSynth.

AviSource("ijs.avi") 
ConvertToYV12(interlaced=true) # dehalo_alpha requires YV12
Separatefields()
Dehalo_alpha(rx=4, ry=2)
Weave()

original on left, dehalo on the right:

[premiumcapture]

You mean the halos at high contrast edges? Those are from over sharpening by the VHS deck. And maybe from your capture device too. If your VHS deck has a sharpness control turn it down. The same goes for your capture device. You can alleviate it with a dehalo filter like dehalo_alpha() in AviSynth.

AviSource("ijs.avi") 
ConvertToYV12(interlaced=true) # dehalo_alpha requires YV12
Separatefields()
Dehalo_alpha(rx=4, ry=2)
Weave()

original on left, dehalo on the right:


[Attachment 31188 - Click to enlarge]

Thanks, does this also result the brown glow around the sword and by the mans arms where the arrows are pointed is also a result of sharpening?

[lordsmurf]

Chroma is offset +
the chroma is smeared (even when offset is fixed, it will bleed over).

Fix offset in Avisynth.
Use VirtualDub CCD to fix the rest.

[premiumcapture]

Thank you for the help LS. I can script it myself, but how can you tell which direction it is offset in? I played with vertical offset and it looked better in some areas and not so in others.

[lordsmurf]

Thank you for the help LS. I can script it myself, but how can you tell which direction it is offset in? I played with vertical offset and it looked better in some areas and not so in others.

That's the bleeding. You have to do as best as possible, then let CCD take over.

[jagabo]

You can see how much to shift the colors by looking at the video. Here's the source video with a big saturation increase (to see the colors better) and the luma channel to the right, then the U and V channels (stretched to the same size as the luma) below:


After sharpening the chroma and shifting up by 4 pixels, right by two pixels:

MergeChroma(aWarpSharp(depth=20))
ChromaShift(l=-4,c=2)

See how the colors align better on the flag and the barrels. The chroma channels in VHS are very low resolution horizontally. About 40 lines across the entire frame.

[premiumcapture]

You can see how much to shift the colors by looking at the video. Here's the source video with a big saturation increase (to see the colors better) and the luma channel to the right, then the U and V channels (stretched to the same size as the luma) below:

[Attachment 31197 - Click to enlarge]

After sharpening the chroma and shifting up by 4 pixels, right by two pixels:

[Attachment 31198 - Click to enlarge]

MergeChroma(aWarpSharp(depth=20))
ChromaShift(l=-4,c=2)

See how the colors align better on the flag and the barrels. The chroma channels in VHS are very low resolution horizontally. About 40 lines across the entire frame.

Awesome, thank you for this! Very insightful.

Just for me to double-check here - I can apply WarpSharp only to chroma, right? Also, when you say that the chroma channels are low resolution, are you saying that this particular issue in the example photos you posted is common to the VHS format? Would this include the sensation of chroma lagging behind luma in some cases?

Sorry for all the questions, but I am learning a lot here and I cant help it

[premiumcapture]

Thank you for the help LS. I can script it myself, but how can you tell which direction it is offset in? I played with vertical offset and it looked better in some areas and not so in others.

That's the bleeding. You have to do as best as possible, then let CCD take over.

Is there a difference between CCD in VirtualDub and AviSynth? In this instance, I can see a difference with CCD but it is relatively weak, and making more than one or two passes begins to kill the color in unintended places in the trouble spots.

[jagabo]

Just for me to double-check here - I can apply WarpSharp only to chroma, right?

Yes. MergeChroma() applies the chroma channels of one video to the luma channel of another.

Also, when you say that the chroma channels are low resolution, are you saying that this particular issue in the example photos you posted is common to the VHS format?

All VHS. I think your video is a little worse than normal though. Probably an n'th generation copy.

Would this include the sensation of chroma lagging behind luma in some cases?

You mean temporally? No. That's more likely to be caused by a digital temporal noise filter.

[premiumcapture]

Would this include the sensation of chroma lagging behind luma in some cases?

You mean temporally? No. That's more likely to be caused by a digital temporal noise filter.

Yes, temporally. Is this a filter inside the VCR? Using a JVC 9800 and AG1980 and getting similar results on both.

[jagabo]

I'm not real familiar with those S-VHS decks but they might have temporal noise filters.

Also be aware that aWarpSharp() requires progressive frames. It will blend the chroma of the two fields together if you use it on interlaced frames. MergeChroma() can be used on interlaced frames -- if both videos are interlaced.

[premiumcapture]

I'm not real familiar with those S-VHS decks but they might have temporal noise filters.

Also be aware that aWarpSharp() requires progressive frames. It will blend the chroma of the two fields together if you use it on interlaced frames. MergeChroma() can be used on interlaced frames -- if both videos are interlaced.

I just realized that between the two copies of the same source I have, the one posted is an nth copy as you suspected. The other one I own is MUCH cleaner. No need for me to freak out about my equipment anymore

Thanks for the help. Between here and the DigitalFaq, I am on my way to have a degree

[lordsmurf]

Low chroma resolution is what causes the bleeding, even after proper alignment.

"Mouse trails" are always a temporal filter done badly.
But it's not just VCRs, or software. You often saw this on 80s camcorders and VCRs, during recording.
Don't be quick to place blame. (That happens too much around here.)

[premiumcapture]

Low chroma resolution is what causes the bleeding, even after proper alignment.

"Mouse trails" are always a temporal filter done badly.
But it's not just VCRs, or software. You often saw this on 80s camcorders and VCRs, during recording.
Don't be quick to place blame. (That happens too much around here.)

By temporal filter, are you talking about bad temporal denoising? Is this usually done by a VCR or is it inherent in most capture equipment? I noticed multi-generational tapes seem to exhibit it very obviously.