The repeating pattern probably follows the brightening and darkening pattern of the AGC-triggering MV pulses in the VBI. The top of your image is also flickering, separately from your main level jumps.
https://gfycat.com/FixedThirstyHummingbird
Small GIF version, if that link dies in future
FixedThirstyHummingbird-size_restricted.gif
MV is still present in your capture, to some degree. See that little white bar visible at the left edge of the head-switching noise? It's a signature of MV in the horizontal blanking interval that has been pushed into the visible picture area due to the head switch causing the image to skew to the right. Not all MV tapes have this, though.
VCR blue back, VSYNC shown at top
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Sweep recorded to VHS, VSYNC shown at top
Raw capture, 525i, Y8 rolling display - PV-S4670 blue back.jpg
Titanic VHS, VSYNC shown in middle. 4 VBI pulses, white VBI bar separated from pulses, plus white bar in HBI.
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Home Alone VHS, VSYNC shown in middle. 5 VBI pulses, white VBI bar right next to pulses, no white bar in HBI.
Raw capture, 525i, Y8 rolling display - PV-S4670 AVIANITA.jpg
There are probably also some residual MV pulses in the vertical blanking interval that weren't removed by the Personal TBC IV, like with the MX-1 video mixer. So the overall point here is that MV was removed enough to trick the drivers into not digitally distorting the signal, but not enough to avoid triggering AGC on the analog input side like a VCR recording would.
http://www.digitalfaq.com/forum/vide...s-showing.html
Quote:
Originally Posted by me
Apparently the MX-1 leaves some residual lines containing MV, while the MV stripper of course over-corrects by also killing the closed caption lines.
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