No problem you are welcome. The mystery it's that now the catalyst recognize the video firewire box but Qt doesn't .
to make it work I've enabled more then just the default 1 video input and it happen that the box was video input number two .
Strange thing tough it's that once I've then disabled the second input the firewire box appear in the first input .
I don't know I know it's sound spaghetti but that's what happen