question about deinterlacing

[DaneClark]

I'm going to try a virtualdub chain for improving vhs encodes that in found online and I was wondering if anything bad would happen if I used a deinterlace filter on something that didn't need it

[KarMa]

Hurts the quality, heavily depends on which deinterlacer you use.

[johnmeyer]

Deinterlacing always degrades the video. There is no way around this because you are tying to "estimate" where one field would be in time in order to match the other field. Once you have deinterlaced, you can never go back.

Progressive video is not "better" than interlaced video, although it is most definitely easier to edit. Once you have interlaced video (like a VHS capture) my advice is to always keep it interlaced, and let your TV do the deinterlacing, if it needs to.

In direct answer to your question, my answer is: I don't know. It would depend on the deinterlacer, as KarMa already said, and also on the nature of your video. The less motion in your video, the less damage most deinterlacers will do.

[jagabo]

The better deinterlacers in VirtualDub try not to deinterlace when not necessary. But they are not perfect and will sometimes deinterlace something that's not interlaced. So if your source isn't interlaced it's best not to apply a deinterlace filter.

[DaneClark]

[Attachment 34899 - Click to enlarge]How can I tell if my source is interlaced or not?

BTW, I have attached a picture of the chain I want to try. My source already looks great. It's a VHS rip of the few Charlie Brown specials that Warner Bros hasn't put out on DVD yet. I just want to color correct it an smooth out the grain and pixelation.

[Brad]

A PAL Charlie Brown cartoon probably used speedup from 24fps with no interlacing. But the fields may not be aligned into full frames ("phase-shifted") and there may be residual interlacing from VHS timebase errors. Not sure what VDub filters exist for dealing with that without deinterlacing when not necessary.

If your goal is to improve the quality, don't resize. Especially not a vertical downsize.

[KarMa]

Assuming this material should be 23.976fps, but was telecined to play on a standard NTSC 29.97fps VHS.

I would use this

LoadPlugin("C:\Megui\Megui\tools\avisynth_plugin\TIVTC.dll") #Use your own TIVTC location
tfm(order=-1).tdecimate()

tfm() will restore the original progressive frames, and tdecimate() will remove the extra duplicate frame every 5 frames. tfm() is selective about field matching, and so won't touch a frame it does not think is interlaced.

[jagabo]

Your image appears to show a PAL (720x576) source. Rare NTSC videos are often converted to PAL with field blending. Videos like that should have the blending removed with QTGMC().SRestore() in AviSynth.

[DaneClark]

No wait, I didn't realize that was a PAL filter chain. I'm working in NTSC. And my encodes look great. There don't seem to be any framerate - related artifacts visible. I'm mostly concerned with color correction and grain reduction.

[DaneClark]

I just need a good filter chain for color correcting and cleaning up VHS cartoons that won't result in color casting or crushed black or white levels while still keeping the picture looking nice and sharp without any grain or pixelation. I know it's possible because I've seen avis of VHS cartoons that look that good.

[DaneClark]

Where did everyone go?

[KarMa]

You started with wanting deinterlacing advice, which eventually led you to decide you don't need to deinterlace but instead need color correcting advice. So that is probably a problem with getting responses.

I'm not a pro a color correcting but I use Tweak() to change the sat/brightnes/contrast/hue, and then use Histogram() to see how it looks like on the scope. Just be sure to delete Histogram() before you encode, as it will become part of the encoded video.

http://avisynth.nl/index.php/Tweak
http://avisynth.nl/index.php/Histogram

I do all this in AvsPmod.

[jagabo]

To check for illegal YUV colors you can use HighlightBadRGB() from this post:

https://forum.videohelp.com/threads/360935-Capturing-Correct-Chroma-and-Hue-Levels-From...=1#post2289672

Or you can use Gavino's more accurate, but much slower, script from earlier in that thread. Only about 1/4 of all possible YUV values are legal.

[KarMa]

nice, forgot about that thread

[jagabo]

As to how get your colors right AviSynth has many filters for adjusting colors and levels: ColorYUV(), Tweak(), AdjustRGB(), Levels().