Minimum lag that generally fast scalers add to rotate is a frame, 16ms. No reason that OSSC will need more time than that. Now if it does some magic and uses scanline buffering instead of frame buffering like MiSTer does it might have a lag of a couple of scanlines which is not noticeable. However scanline buffering might not be compatible with all LCDs.
1 frame of latency can be noticeable if you keep switching between CRT and LCD, but I doubt if you are playing only on LCD that you will ever notice it. 40ms of lag is def noticeable if you know how the game behaves.
I would have loved if it downscaled as well. 1080p to 240p quickly, that would have been an instant buy for me.
Ok, I’ll ask, why the hell do you want to scale 1080p to 240p? You realize that means eliminating a shit ton of pixels. It will never be good. You want to turn over 2 million pixels into around 77,000. You expect that to be good quality and instant? 1080 content was designed for high resolution. I can understand wanting to display sd content on a sd display, I have consoles connected to pvms, I can also understand upscaling because that works and can be nice and sharp and quick and look decent, but I can’t understand what you are asking for. If you really want to do it, there are processors out there and it sucks.
People want to scale 240p to 1080p.
The problem is 1080 is not an integer of 240 ex: 240<480<720<960. The 4x integer is 960 which doesn’t fit into a 1080.
So you got these black bars on top and bottom of image, squeezed square pixels (improper aspect ratio), and if you are playing on a 4K device, you can pray to your 1080 to 4K built in upscaling gods.
The scaling to a 4K resolution would allow you a perfect 9x 4K {240x9=2160}
Allowing LCDs to display black bars on the side of their image instead of top and bottom.
If perfect scaling is achieved the aspect is still too narrow unfortunately.