Hi,
If i try to preview an html5 ogv video before publishing it, i have the information that "Video format or MIME type is not supported." When i publish the video, edit it again and try to preview it, then i can see it with.
So it seems that the problem is happening before we publish it.

Steps to reproduce

- Create a new class with a "Media" attribute with HTML5 video parameter
- create an object of the created class, with am "ogv" video, with "Controller:" checked
- Before publishing the video, try to preview it