While the app is based on video.js I found an issue on Github:
There it’s said:
Video.js passes the mime type you supply directly to the browser to check if the type is supported, so if video/quicktime doesn’t work, then the browser is saying it can’t support it. Or there’s an error in the file that’s blocking playback.
So maybe it works with another browser or maybe you just need a quicktime plugin (don’t know if there is one for Chrome).
This change just had the result, that neither mov nor mp4 played in the NC video player. It is now offered to be downloaded.
I undid the change and can now again play mp4 on the server. But as before, mov and mkv won’t play and only through an error message, that the file type is not supported. I use Firefox 58.
This old question has been mine too and now I decided to convert all my iphone .mov and .mp4 files. So I just installed ffmpeg and all its dependencies and the nextcloud video converter app on my debian stretch nextcloud and NAS server.
Just did that and abrakadabra - all videos are playing just fine without converting. Simple solution. I just never installed ffmpeg because it depends on X11-common, what I never wanted on a server.