I should add a video to a survey, it should have sounds, and it should be possible to see only once. (Some kind of test or exam, got the request from a researcher.)
Of course there must be first some other page showing a video so that the user can set up volume level etc. Then, I can add a video by direct HTML code, <video autoplay muted>, and use timer to put some time limit to the [pseudo]question showing video. But autoplay only works if the video has no sound. So is there anything I can do, like some JS that would start timer when the user starts looking video?