Thanks for taking time to look into this issue. I think the OSSC is a seriously great product and I love it, so I don’t mean any disrespect by saying that I think this is an issue with the OSSC and nothing else.
Let me clarify the issue exactly.
I only use PAL PS1 software but its irrelevant in regards to this, as the problem occurs if there is no game in the console.
It’s not the display, my primary TV is an LG TV and once the shimmer has started to test I have moved the HDMI to my secondary Samsung TV and the shimmer still occurs.
To fix I change the input on the OSSC then change the input back. This fixes the issue until the PS1 restarts. There are no shimmer effects reoccurring from 240p to 480i transitions.
Turning the OSSC on and off also stops the shimmer effect and also turning the OSSC off once the shimmer effect has gone does not make it come back.
There is only one place the shimmer effect occurs and that is if the OSSC is already on during PS1 boot/restart and the Sony Enternainment screen is displayed (White background and orange diamond). If you turn the OSSC on after boot the shimmer effect doesn’t happen.
Something to note when the shimmer is occurring the OSSC shows 49.88Hz.
After either turning the OSSC off and on, or changing input making it work fine again the OSSC shows 50.00Hz.
(This is on the PS1 boot and menu screen that shows Memory Card and CD Player)
I hope that clarifies everything and sorry if I’ve come across rude in anyway or misinformed.
I’m hopeful there can be a firmware update that maybe could fix this issue but to be honest it’s no major gripe as it’s simple to remedy and will last until you restart the PS1.