Input Video Format Detection in AD9984A

Hi,

When trying to use AD9984A for YPbPr and PC Graphic Video input to digital conversion, How can I detect the input video resolution(or format) ?

I think it could be decided by Hsync counts per Vsync and other parameters.
Can somebody explain it in detail with an example ?

  - Which registers or values should I check ? From them How can I determine its resolution or format ?

Thanks.