It can be a nightmare searching.
Quickly, it can be the aspect ratio of the picture, it really needs to
conform to around the 4.3 video size, so if you have cropped it and it's now
6.3 it won't come out properly. If the resolution is low and you have used
an effect on it it won't help. PC screens do not show off picrures to there
best, have you exported it and watched it on a tv to see how it looks?