VideoHelp Forum

Try DVDFab and download streaming video, copy, convert or make Blu-rays,DVDs! Download free trial !
+ Reply to Thread
Results 1 to 4 of 4
  1. Member
    Join Date
    Jul 2007
    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

Name:	70fRKS6.png
Views:	105
Size:	114.4 KB
ID:	45064
    Click image for larger version

Name:	EIsatm9.png
Views:	67
Size:	139.5 KB
ID:	45065

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

Name:	UayEBB4.png
Views:	75
Size:	102.7 KB
ID:	45066

    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.
    Quote Quote  
  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

Name:	EIsatm9.jpg
Views:	30
Size:	58.6 KB
ID:	45067

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

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

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

    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

Name:	reflect.jpg
Views:	29
Size:	13.8 KB
ID:	45068

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

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

Name:	stretch.jpg
Views:	29
Size:	13.8 KB
ID:	45069
    Quote Quote  
  4. Image
    [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.
    Last edited by raffriff42; 1st Apr 2018 at 08:39.
    Quote Quote  

Similar Threads