Bad Video Picture on SDL 1.3 Windows PC porting

I tried using SDL 1.3 for Media playback .
Video APIs are changed a lot , but they are more friendly I think.

New d3d render is applied. The Video picture itself is 320*240, and the
video window is like a “wide screen”.
Then we see the blank area is not black. see attached picture.
http://www.nabble.com/file/p26071100/sdl_1_3.jpg

Can D3D experts explain this in more details?
thanks.

Xinghua–
View this message in context: http://www.nabble.com/Bad-Video-Picture-on-SDL-1.3-Windows-PC-porting-tp26071100p26071100.html
Sent from the SDL mailing list archive at Nabble.com.