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原来是旧式电视信号同步出了差错
电视信号一次发送 1 条水平线,并在屏幕上按顺序绘制,当到达底部时,它会返回停止并重新开始。
What causes the picture to roll over on old TV sets?
nickasummers · 8 yr. ago
Its eli5 so ill take a few liberties when it comes to reality. Also, I don't actually know TV tech, im a game developer and i heard an explaination of how this effect was intentionally achieved for a game, so this might not actually be why it DOES happen, but its certainly a way it could happen that shows how it isnt magic
Tv signals are sent 1 horizontal line at a time and drawn sequentially down the screen and when he bottom is reached it goes back to the stop and starts over. if it gets out of sync with incoming data, say, if it thought there were supposed to be 3 lines per picture when really there are 4, this happens:
frame 1
11111
22222
33333
frame 2
44444
11111
22222
Im honestly not sure how the desync happens, and the number of lines is, uh, significantly more than 3. also extra data coming in could concievably cause this:
frame 1
11111
02222
20333
33044
frame 2
44401
etc |
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