Overview: Preview thumbnails
Preview thumbnails associate representative pictures with an episode or a navigable point within media.
An episode thumbnail helps identify a programme; a chapter thumbnail represents a position used for navigation. Both may be derived from media, but they attach to different library relationships. Catalogue identity and navigation position give each kind of preview its own association.
Episode thumbnails
An episode thumbnail is associated with a particular episode presentation or record, which can differ from series artwork and locally extracted frame previews.Chapter thumbnails
A chapter thumbnail associates a rendered frame preview with a programme position, requiring the selected source, time mapping and image derivative to remain coherent.