So the OSSC is an FPGA controlled TVP7002 which is a brilliant idea. 🙂
If I understand correctly PLL stabilizes the HSync because HSync is somehow unstable or distorted when VSync is active?;
and H-PLL pre/post coast are the region in time where the PLL locks/unlocks a more stable HSync signal while the VSync does its job and replaces the unstable HSync with the fixed-HSync while it’s active.
Now that raises few question;
Why the analog HSync during Vsync so distorted that it requires fixing before digitization?
Why some consoles require more than other?
How a CRT handles it?