Remove semi-transparant Purple/green line at top of analogue video?

[Killer3737]

I have a video captured from a Video8 tape. A friend of a friend did the capture and whilst I don't know what the cause is, a new transfer isn't currently possible, so I have to work with what I have. The video has a 10px line at the top over the image that is semi-transparant, you can see the video below it.

Most of the time it's purple:



Some times it's green:


Other times it's not there at all.

Is there anything I can do to fix this, rather than just cropping it out and losing those 10 lines? Using AviSynth, video is lossless UT Video.

[poisondeathray]

Problem with v channel inversion

You can filter the top by cropping, inverting the v channel, stackvertical back onto the original. But you won't find a strip not quite matching from probably from chroma subsampling and some compression artifacts / rounding. You can crop 1px values if you use YV24, but the edge blurring occurred farther in the past. Maybe you can reduce it father buy applying a denoiser through a mask



This is for the image, you would adjust for the video

ImageSource("EIsatm9.png")
converttoyv24()
a=last

a
crop(0,0,0,-131,true)
a1=last

a
crop(0,11,0,0,true)
a2=last

u_chroma = UToY(a1)
v_chroma = VToY(a1).invert()
YToUV(u_chroma, v_chroma)
MergeLuma(a1)
a1f=last

stackvertical(a1f,a2)

Other times it's not there at all.

Then you might need some detection script, with logic . Maybe conditionalfilter or conditionalselect if you don't want to manually identify which sections to apply

[jagabo]

Another way to hide it is to reflect colors from lower in the frame up over the bad colors:

STRIP_HEIGHT = 14
top = Crop(0,0,width,STRIP_HEIGHT)
bottom = Crop(0,STRIP_HEIGHT,width,STRIP_HEIGHT).FlipVertical()
top = MergeChroma(top, bottom)
Overlay(last, top)

Or stretch the chroma from below the bad strip up over the bad strip:

STRIP_HEIGHT = 14
strip = Crop(0,STRIP_HEIGHT,width,STRIP_HEIGHT).BilinearResize(width, STRIP_HEIGHT*2)
Overlay(last, strip, mode="chroma")

[raffriff42]

[Attachment 45072 - Click to enlarge]


[Attachment 45070 - Click to enlarge]

I believe the top strip has its R and G channels swapped.
But there are other issues (level shifts, gradients) that will make actual repair very difficult.