Camera Tracking problem

Hi everyone,

Would you know any good English/French tutorials to create 3D Camera Tracking in Blender (v2.76b).

I keep getting weird shadows when I try or shivering images: when I select “set as background” and “setup tracking scene” there is a part of my scene that is darker (and therefore visible), which is not normal. My cube has no shadow and the video is disproportionate (see picture attached : http://www.zupimages.net/viewer.php?id=16/53/05iq.png).

Could you please give me a hand with that?

Thanks a lot for your help,

SmartRmax