Bad interlace lines on progressive video

[PanMarSag]

Hello, can someone tell me how to remove those weird bad interlace lines on video that is progressive? Maybe some AviSynth script would help.

[Selur]

Without a short sample of the file you use as source: no

[PanMarSag]

Here's the short sample of file:
cnpolandecpnextbumpereliotkid.mp4

[johnmeyer]

Those were caused by re-sizing interlaced video without first deinterlacing. They are horizontal lines, but as you can see, they are much taller than a single scan line and are therefore not "interlace lines."

They cannot easily be repaired, although I did come up with a way to dramatically reduce the problem when I helped someone years ago over in doom9.org. Here is a link to that thread:

repair bad deinterlacing

I never took the extra time to generalize the code into a function, so you'll have to tweak it for your frame rate and resolution.

[edit] Post #42 in the thread I linked to has the "final" code that I posted. However, remember that it will not work on your clip without tweaking.

[Selur]

something like:

Spline36Resize(640,240)
AssumeTFF()
QTGMC(Preset="Fast")
Spline36Resize(640,480)

should work. (basically throwing away half of the height)

[jagabo]

You can reduce the damage by only applying the fix to areas where there are comb artifacts.

###################################################
#
# build a mask of areas where there are 
# alternating horizontal lines
#
##################################################

function CombMask(clip v, int "threshold")
{
    threshold = default(threshold, 5)

    Subtract(v, v.blur(0.0, 1.0).Sharpen(0.0, 0.6))
    GeneralConvolution(0, "
        0  8  8  8  0
       -0 -8 -8 -8 -0 
        0  8  8  8  0
       -0 -8 -8 -8 -0
        0  8  8  8  0", chroma=false, alpha=false)
    mt_lut("x 125 - abs")
    mt_binarize(threshold) # threshold
    mt_inpand()
    mt_expand()
    mt_expand(chroma="-128")
}

##################################################

src = LSMASHVideoSource("cnpolandecpnextbumpereliotkid.mp4").AssumeTFF()

combmask = CombMask(src, 5).Blur(1.4).Blur(1.4)
blurry = Spline36Resize(src, src.width, src.height/3).Spline36Resize(src.width, src.height)

Overlay(src, blurry, mask=combmask)