Split screen

C

ClaireM

New Member
I’m a complete novice and a slight technophobe, so some help would be greatly appreciated.
I am converting old family videotapes to digital. The tapes play perfectly on the TV screen but the image in the app, which records fine, is split so that the heads are at the bottom and feet at the top of the screen. How can I adjust this so that the images are centred
 
A

AaronD

Active Member
For a little sneak peek under the hood, there are three separate things happening at the same time here:
  • Color/brightness as one single dot
    • (for a black and white example, imagine a single dimmer switch on the wall, that changes much faster than you can see, and it's limited to the size of a laser pointer...)
  • Horizontal sync
  • Vertical sync
The sync signals are pulses that happen at specific times to keep the screen aligned with the camera. Meanwhile, the color/brightness changes value as the single dot flies across the screen. It "flies to the right" on its own and resets to the left with the H sync, and it "falls down" on its own and resets to the top with the V sync. The speed is adjusted so that the single dot traverses the screen exactly between sync pulses. And both the screen and your eyes continue to show whatever color/brightness the single dot had when it was last in each position.

To produce your problem, your capture card is simply not getting the V sync, and so it resets *itself* to the top in an attempt to make *something* work, with no idea of what it *should* be doing.

TV's are generally pretty good at picking out a bad sync, because an analog TV broadcast is that same signal on an AM radio. Capture cards, not so much.
 
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