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  1. Member
    Join Date
    Jul 2007
    Location
    United Kingdom
    Search Comp PM
    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:
    Click image for larger version

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    Click image for larger version

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    Some times it's green:
    Click image for larger version

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    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.
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  2. 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

    Click image for larger version

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

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

    Code:
    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)
    Click image for larger version

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

    Code:
    STRIP_HEIGHT = 14
    strip = Crop(0,STRIP_HEIGHT,width,STRIP_HEIGHT).BilinearResize(width, STRIP_HEIGHT*2)
    Overlay(last, strip, mode="chroma")
    Click image for larger version

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  4. Image
    [Attachment 45072 - Click to enlarge]


    Image
    [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.
    Last edited by raffriff42; 1st Apr 2018 at 08:39.
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