I want to add a video to my course.

I have an mp4 video and I have the same video in ogv version. 

In the builder the media component shows a still/diashow from the video. So I guess the builder is able to read the video. However when I press preview,I only get a placeholder with a play button. When I press play on the videoarea it does nothing. when I press play in the controls underneath, it starts loading (circling loading icon) but never do I see any playback.

Is this not working in the preview? or is something wrong in the videoformat? or do I need to do something else?