video not able to fallback to flash in ie8

Hi,

I’m using the new mediaelement.js capabilities to embed my videos in my wp site, but i run into a problem when viewing pages containing videos on IE8.
here is the shortcode i use:
[video width="640px" height="368px" mp4="http://mysite.com/myvideo.mp4" webm="http://mysite.com/myvideo.webm"][/video]

Everything works fine on most devices, using chrome, firefox, android…
but on ie8, the library is supposed to use flash fallback, but it doens’nt, i can click play but i have a black zone (the 640x368px), and just the sound, the progress bar does not move, and the time counter stays to 00:00. When i right click on the black “zone”, i have no flash controls, so i guess it’s just trying to load the mp4, but can’t render the video.

Thank you, any help appreciated.