Problem of putting Controls on a Video

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C#

DirectX

When there is no video at the back, everything are no problem. All the controls' backcolor is transparent and they have a image background(TGA format).
http://img834.imageshack.us/img834/1606/problemnormal.png[^]

But if I put a video between the background of the form and the controls.
Although I set the controls as transparent, the controls' background become the background of the form but not the video.
http://img40.imageshack.us/img40/8155/problemtransparent.png[^]
(I set the background color as black so the problem may be not easy to identify)

Also if I use the transparency key (black), I got a terrible result!!
The background of the controls become fully transparent and they can show me the desktop. Even the color of the ideo that same as the color of transparency key become transparent.
http://img190.imageshack.us/img190/7398/problemtransparencykey.png[^]

I am using the Microsoft.DirectX.AudioVideoPlayback to play the video.
And when I search on the Internet, some people said that it cannot be solved.
So I hope someone in this site can help me to solve this problem.