Totem uses a visualization plugin to display visual effects while playing audio。This includes generating thumbnails of video files when browsing in Nautilus and a video plugin for Netscape-compatible browsers (e.g. Firefox).Totem Movie Player automatically loads and displays subtitles if the file that contains them has the same name as the video file and has an asc, txt, sub, smi, or ssa file extension.
Reference：https://projects.gnome.org/totem/