Video files under 15 seconds (mobile)

Lets say i sent a pic of a plastic bag stuck in a tree to a friend. Cool anyone can. let's step it up, its a still image i want to record a 15 second or shorter clip of the plastic bag, flowing through the wind. which would make him laugh. cause you know, memes. regardless there are other times I'd like to send short clips to friends. unsure if its the formatting my phone records in or if discord just don't accept video files. or a built in "record a moment" feature for mobile users.