We have local stored video that we display using the media module and Video in field views.
In a view with several videos only a few gets a thumbnail image representing the video. This configuration:
Controls: visible Autoplay: nej Loop: nej Muted: nej Size: 100% x 225 Multiple files: tags Field template: Drupal default
With Firefox we got 90 % of the videos with image preview and with Chromium 50 %.