tvctl on distorts image in NTSC

[nutki]

The change in 8d7bd58 causes tvctl to shift the even field display area up by 1 instead of the previous 2. Since the odd field is still shifted by 2, this causes a misalignment in the video display.
I have a PR that attempts to use the proper lines without modifying tvctl.
Maybe @ZXGuesser could verify this works as I don't have any device to decode CEA608 CC.

[ZXGuesser]

Yup that seems to be working, at least as far as the demo code repeating "hello!" is concerned with the datastream going in the first field.