Timing of Vertical Sync Pulse on Composite Video

[PConst167]

Hi friends,

For you who understand about how old CRT tv's work....... Or even new ones that accept composite input...

What would happen in the vertical sync pulse were one line longer than normal? What if the total length is actually 320us rather than 160us ?

That is, 4 lines rather than 2.5 ? I have tried this and no problems, however I'd like to know how the TV deals with this... Does it just ignore the remaining integrated voltage after pushing the electron beam? Or Does the beam stay up there for a little longer ?

Thanks a lot

 

[Nigel Goodwin]

It would depend entirely on the particular TV, very old analogue ones would almost certainly cope perfectly well, but more modern digital ones (and some IC based analogue ones) may have problems, depending on their design.