VIP Suite Frame Buffer issue

Hi,

I'd like to use the Frame Buffer function in a simple design :

Clocked Video Input -> Frame Buffer -> Clocked Video Output

And it doesn't work (black screen).

I tried this design before :

CVI -> CVO

and it works.

I looked with SignalTap the signals between the CVI and the FB and nothing happened.

Can anyone explain me how to resolve this problem, please?

Thanks

Dath