Sounds like it just has a built in scart RGB upscaler in the box. This device I use can go from 720-1080 with my pc engine. http://www.ebay.com/itm/Scart-to-HDMI-Video-With-3-5mm-and-Coaxial-Audio-Converter-Box-1080P-Upscaler-/391441849877?hash=item5b23c09e15:g:XnQAAOSwAuNW4O9G Also has the very minor shutter every 5-6 seconds if the game is scrolling very fast without any pause anywhere.
The upergrafx uses only the digital signals, bypasses the RGB ADCs, and stores the digital values into a frame buffer, and re-synthesizes the output to the different scanning format based on the framebuffer in digital format.
Does the EXT port provide the digital signals directly from the PPU?
I'm not sure about the refresh rates being different causing 1 frame drops. Since the refresh rates wouldn't be any different. The ATSC standard which is the HDTV standard supports multiple refresh rates, including the refresh rates from NTSC. Quote from: Joe Redifer on April 30, 2016, 12:17:38 PMDoes the EXT port provide the digital signals directly from the PPU?That's a good question everything I've seen seems to point to it just sending the RGB and sync signal. The dude at db-elec might be able to answer that question since he makes a Grafx Booster for the Turbo Grafx (and I think core grafx) that allows you to get RGB, and SVideo out, and he does so by tapping into the ext port. http://db-electronics.ca/product/dbgrafx-booster-ttp/
Could the game be programmed to switch between mode at each field? So when it's combined on video output, it'd be true 525 lines for proper NTSC standard? Or is switching video mode a little slow to do in the vertical banking?
I wonder if the Framemeister would hate it. It can't stand the interlaced mode on Sonic 2 and Ys 3 on the Genesis.