What kind of noise is this?

[Sharc]

The captures of some of my VHS tapes show this kind of noise (http://www.mediafire.com/file/a4ps338hpi9sqx3/VHS_sample.ts). Is this typical for a certain defect, e.g. due to an aged tape or due to a problem with the capturing HW? The video signal is composite, so I thought it could be excessive dotcrawl. It is however not the same for all tapes, some are almost free of this kind of noise.
Any thoughts or suggestions how to fix it?
Thanks.

[Mounir]

Secam tape eh ? You probably need a better vcr, it'll be hard to remove that ugliness now

[Sharc]

No, it's PAL. I'll try to find another VCR or videocam to play the tape back via different HW and see whether it makes a difference. And yes, it's probably impossible to remove this noise without spoiling the rest.

[Mick]

@Sharc
this Noise is in the "Chroma" Part. My Tip: Try S-Video instead of Composite and use VirtualDub with enabled "Noise Reduction". Set the Slider for the Noise Reduction not too high to avoid "smearing". Which Codec did you use for capturing ?

Cheers
Mick

[Sharc]

@Mick
My VHS player does not support S-Video which would eliminate the Luma/Chroma crosstalk of Composite as you mention. I have some doubt if it would really help because other tapes are much much better. I think its the tape itself which is bad.
I had some success with
separatefields()
bilinearresize(480,256).spline36resize(720,288) #downscale - upscale, proved to be most effective
temporalsoften(4,4,8,10,mode=2)
fluxsmoothST(3,3)
weave()

[jmac698]

Someone really needs to implement the bbc pal decoder as a plugin.

[TlatoSMD]

The red flicker looks very typical of faulty cables or improperly attached connectors to me. Plus it has a moire pattern as if either source or receiving device gives or expects an S-VHS signal but the other side is just set to composite. Try and see what happens if you wiggle the connectors, use a new cable, and fiddle with the S-VHS vs. composite setting on either the source or receiving device. Of course, it could well be the fault already happened when the original VHS-C or Video8/Hi-8 tape was copied to a regular VHS, so it's already within your copy.

Oh, and what's wrong with the aspect ratio? It looks like you've zoomed into a 4:3 image to avoid pillarboxing in 16:9, and then encoded the resulting 16:9 footage with a CinemaScope aka Panavision aspect ratio of 1:2.35.

As a last resort when you can't eliminate the artifacts by looking into the hardware setup, I'd recommend Tacosalad's Dotcrawl filter: http://home.earthlink.net/~tacosalad/video/dotcrawl.html (set to Trellis correlation and Multi-path minimum delta), then MSU Smart Sharpen (http://www.compression.ru/video/smart_sharpen/index_en.html ; options set to your own discretion in combination with the next filter), then the old version of MSU Denoiser (http://www.compression.ru/video/denoising/src/msu_denoiser_161.zip , protip: a bigger temporal denoise figure produces less visual artifacts than with most other temporal denoiser filters), all in one pass in VDub. BTW: Movement artifacts from the Dotcrawl filter, while more visible on single frames or slow-moving footage, can be reduced a bit by means of MSU's old Deblocking filter http://www.compression.ru/video/deblocking/index_en.html at the bottom of the filter chain.

If that's not enough, add HQ smoothing ( http://www.doki.ca/filters/ ), or add MSU's Cartoon Restore in advanced mode and set it to a high value on certain factors. Use either or both at the bottom of the filter chain made up of the other filters above.

Lastly while not directly related, I don't know about the BBC PAL filter but somebody really needs to at last write the cross-color and cross-luma PAL filter for VDub that Tacosalad has announced already more than a decade ago. I've mailed him about him around 2005 and he said he has "all the math in his head" for a genuine PAL version of his Dotcrawl filter with that, but nothing doing so far. MSU has been faster and implemented the thing in their commercial MSU Tuner TV Restore filter: http://www.compression.ru/video/tuner_tv_restore/index_en.html (look at the guy's shirt to see what I mean). Well, we need either that, or a proper GUI for Avisynth at least. After all, I'm just a button clicker, not a programmer.

[Sharc]

Thanks for your suggestions, TlatoSMD.
I can rule out any cable or loose connectors issues. I think it's really in the tape itself (duped version, or defects due to aging).

Don't worry about the Aspect Ratio. I just cropped the picture to show the ugly part of it only. Sorry, I should have mentioned this to avoid confusion.

Tacosalads's filter: I saw this, but he wrote:
PAL users: Sorry guys, this filter doesn’t fix PAL rainbows and dots. I just got my hands on some PAL specifications, and my algorithms all require some adjustments before they’ll work. Eventually. Soon, I hope!
So I didn't even try.

I will try your MSU suggestions, but I think some require a license.

I'll report back when I find something which is noticeably better than what I already did. Thanks again.

[TlatoSMD]

Oh, Tacosalad's Dotcrawl filter wasn't written for PAL indeed and that's why it doesn't do what it says on the box (or in his sample pix) when using it for PAL video. However, it can be used as one rather efficient general noise filter in PAL at least when using the settings I've mentioned above, especially in combination with MSU's Smart Sharpen and MSU's old Denoiser filter next in line during the same cleaning pass. In PAL, Tacosalad's Dotcrawl filter not only denoises the image but also sharpens it at the same time.

Granted, when there's fast motions or moving vertical lines, it also produces artifacts that can look nasty on individual frames or in slo-mo, but a.) those artifacts are less noticeable when the video is running at full 25fps again, and b.) adding MSU's old Deblocking filter at the very bottom of the filter chain somewhat takes care of them.

All the MSU filters I've linked above are freeware, except for Tuner TV Restore, which is the only filter (outside of cryptic AviSynth) I've ever seen that does actually take care specifically of PAL cross-color and cross-luma. Only linked that one filter to say somebody really needs to come up with a simply freeware PAL filter to do that, after Tacosalad has been promising it for over a decade and MSU has already implemented it into a commercial filter.

As for the aspect ratio, your video file didn't only look cropped. The trees also looked vertically crushed, so I set VLC to 16:9 during playback, and that's when the trees looked normal.

[TlatoSMD]

So how's the results been so far, with or without Tacosalad's Dotcrawl filter?

[Sharc]

Tacosalad's filter works very well on NTSC sources with "normal" dotcrawl, however it had hardly any effect on my PAL source.
The other free filters from MSU are more suitable for final fine tuning rather than helping with the basic problem.
My butcher's method seems still to be most effective so far...... although not satisfactory. The noise is just too heavy to have it suppressed without damaging the rest, I believe.

[TlatoSMD]

Dotcrawl only does things on frames in sequence, not on single frames like many or most other filters. That's why you're not seeing much unless you hit preview play and wait a second or two.

[Sharc]

I know with the sequence. But the problem is that Scott Elliot's (aka Tacosalad) filter has no PAL mode.
- works well on NTSC material (I tested it)
- has little to no effect on PAL material (I tested it).
There are avisynth plugins like guavacomb which claim to support PAL for dotcrawl, however even those could not repair the bad source.

Some improvement I got with:

#step1
clip=converttoyv12(clip,interlaced=true)
chroma = checkmate(clip,thr=12,max=25,tthr2=25)
luma = checkmate(clip,thr=12,max=25,tthr2=0)
step1 = MergeChroma(luma,chroma)

#step2
step2=separatefields(step1).bilinearresize(480,288).spline36resize(720,288)
step2=temporalsoften(step2,4,4,8,10,mode=2).fluxsmoothST(3,3)
final=weave(step2)

return final