Phredreeke, on Wed Jun 13, 2012 2:00 AM, said:
(FYI, Pac-man shows each ghost only 1 out of 4 frames, so if you wanted to show "all at once" you'd have to blend 4 frames together...)
Yes, this is the main issue. The 'phosphor' mode in Stella is somewhat limited in that (a) it only mixes the past two frames, and (b) it isn't an entirely accurate representation of a real TV anyway. Basically, Stella phosphor mode is optimized for what's called '30Hz flicker', where the objects alternate every other screen. Pac-man (for the ghosts at least) uses 15Hz flicker (or alternate every 4 frames).
Besides, on every CRT TV and monitor I've tried, there is still some flicker even in 30Hz mode. I'll be trying to more accurately emulate this in future versions of Stella, because the current implementation is very idealized (in that there's no flicker at all
EDIT: I forgot to add that phosphor mode in Stella is currently enabled per-ROM, which doesn't really make sense realistically. You turn it on for ROMs that use 30Hz flicker (or the output flickers too much), and you turn if off for those that don't need it (or the output 'smears'). This alone should show that the implementation isn't ideal. It should be a function of the TV, not the ROM. When you play a game with flicker on a real TV, the TV doesn't know what ROM you're using!