[ADV7511W] Unused input pins.

Hi,

I have a question about unused input pins of ADV7511W.

The ADV7511W_Hardware_Users_Guide.pdf says as follows:
     6.1.1 Unused Inputs
     Any input data signals which are not used should be connected to ground.

Question:
Is it OK that the unused input pins are connected to ground directly?
Or
Should we use pull-down resistance to be connected to ground?
If we should use pull-down resistance, how much ohm of resistance should we use?
1kohm, 4.7kohm or 10kohm? etc.

Thank you!
Best regards.
Tamu