clicked coordinates not correctly displayed in a video player

[qt_user]

I have made a video player. In it , I display the video on a labe. I now want to display a line on two clicks of the mouse. For that I implemented the overloaded mousepressEvent() function, retrieved the coordinates(mouseEvent->x(),mouseEvent->y() ) and displayed then on a frame(laid on a pixmap over the label) using a painter(on a QPixmap) but the line is being made shifted above from the original points and the line is also scaled to a lesser value as if the coordinates are displayed with respect to the whole video player and not with respect to the label.............
What should I do to correct this(i don't have the code right now)....plz help........thanx in advance