HI there , D tube uses html5 (markup language for structuring and presenting content on the worldwide web). Find some useful information about the video formats that are accepted by such a markup language. https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats

A format that always works for me is mp4 /h.264(audio)
This is your standard format when you export from windows movie maker.Hope this helps