Ok, I don’t understand anything of the discussion anymore, but it is safe for me to assume that the video thumbnail as preview image is to complicated for me to achieve.
@texnixe, would this be a reasonable feature to request? If so, I would write up a feature request. Actually I think the whole video file format could need some love. In my projects, I almost always need images side by side next to videos and find it very unfortunate that with images you have a wealth of metadata and with video files almost none.