Comment 4 for bug 604333

comment from upstream:

"The videos you're using have keyframes which are too far apart; when the
thumbnailer tries to seek to a position between two keyframes, GStreamer
instead seeks it to the nearest keyframe it can find. If you've got it set to
do a high number of screenshots, this will result in duplicate screenshots. The
solution is to reduce the number of screenshots taken.

More accurate seeking is bug #619788.
"

That's a gstreamer issue so i'm reassigning this report, thanks.