Cameras are on the belly and the fin normally.
Terrible pic but here's the 777 "forward" cam. The 777 down camera probably just looks like a little porthole in the bottom of the fuselage.
That's the nose gear camera for the Ground Manoeuvre Camera System for the flightdeck only.
The cameras for the IFE are located forward of that, just behind the radome on the underside. Both the forward and downward cameras are located in this place.
The location is slightly left of the fuselage centreline, that's why the IFE image looks a little skewed when the aircraft is in a bank and turn.
The cameras can be seen here, behind the small dark panel, just aft of the radome.