Originally Posted by Supamax
No. Normal RGB Amiga signal (15 KHz) is always outputting in *interlaced* 50Hz mode.
It never outputs a 288p progressive signal. Never.
So the assumption that the output signal is always 576i is correct.
In non-interlaced PAL, the Amiga outputs 50 frames per second as well as 50 fields per second. If it was indeed interlaced, it would be field rate = 2 x frame rate. Since all fields are on top of each other, it is a progressive mode, not interlaced.
This looks like a cool project, and we need to good converter between 288p@50Hz RGB and HDMI@50Hz for smooth motion. Perhaps 1920x1080 would be best suitable as 1080/4=270. With some scanline emulation, each input line could be made into two output lines and then two black lines (or light reduced lines), so to not require non-integer scaling.