I needed to downsize a 20 minute 700 Mb video to under 300 Mb and decided to use VLC. It worked fine, except that the first 10 seconds of video was replaced by a black screen - after that the video was fine, but I am missing the first 10 seconds (audio was fine from the start). I tried various different settings, but this always resulted in the first 10 seconds of video showing up as a black screen.