816x has 3 HD (DVO1/DVO2/HDCOMP) and 1 SD (SDVENC) display vencs
On VVDN HD SDI reference design the connection are:
DVO1/HDMI - On Chip HDMI output
DVO2 ->SIL9022A -> Off chip HDMI output
HDCOMP -> ths7360 -> VGA (Display is tied to HDMI display)
SD Venc -> Composite
I don't have VVDN HD SDI reference design with me but looking at the usecase it appears
nothing is output on DVO2 ->SIL9022A -> Off chip HDMI output path
Do you want to modify the hardware to
DVO2 ->SDI Transmitter -> SDI output
and make the corresponding usecase changes ?