Error in picture

[pernavoi]

I have this strange error on only one channel. At upper left corner of piture(first row of picture or even above) there is horizontal line length about two thirds of the picture width. Line is thin and consist kind of from black and white blocks about 1cm per block.

 

What can cause this? It looks very annoying.

[Derrick]

This is not an error but probably WSS (wide screen signaling). Though it is a remainder from analog TV, many providers still use it. On a normal tv screen it is not visible (overscan).