watching anime with chromecast?

so how do i watch my downloaded files without getting a black screen? i get audio but no video and to answer the inevitable questions:

yes i tried a different player, didnt work

yes i tried changing the extension/reencoding it, didnt work

yes everything else ive tried works except this

no im not installing whatever plex is or anything else for that matter, i shouldnt have to have multiple programs running just to get this to work.