I've got a situation where I have a video, and on the left of the screen for the duration of about one second, I have an unwanted artifact, it's black/grey and in the shape of a triangle. I've got a black blurred border around the whole video anyway, but it's still showing through for that one second. Just to make it clearer, it doesn't just flash up then go again, it appears from out of the side of the left of the screen, then goes away again.
Is there any way, for the short duration that it is visible, to make it 'fit in' with the black blurred border that's already sort of covering it, therefore making it just appear as part of the border? It doesn't stretch beyond the inner edge of the border, so I'm really just looking for a way to make the colour of the artifact and the colour of the border match.
I know the easiest way would be to just make the border black solid, or make it thicker, but unfortunately that's not an option.
Thanks in advance, I hope that wasn't too complicated...!