Tested over multiple samples

When plotting the extents of Start / End within a line and also the line numbers I have identified these:

• negative video line numbers for dropouts
• PAL + NTSC max dropout start is after max dropout end (thought they were cut at the end of a line)
• Without negative lines 0-313 is is 314 inclusive which is higher than 0-312 expected (625/2 = 312.5 rounded up for half line)