The SNES modifies the TV's input signal so that the vertical shifting doesn't occur ('progressive').

This is how you get a 'frame' (448 lines) at 30 Hz. Normal operation ('interlaced') is that every second field is shifted vertically a bit, so the lines of that field end up between the lines of the previous field (which is still visible due to the phosphor's afterglow). Older consoles are slow and support only a limited number of these 'pixels'. The number of pixels per line is simply how often the input signal changes the 'color' of the beam. Remember that TVs don't receive bitmaps, they receive signals that control certain parameters.Īn analog NTSC TV set always draws the picture with an electron beam that goes from top to bottom 60 times per second, drawing 224 lines from left to right. In interlace mode, even/odd fields are sent like classic broadcasts, and you get 448i wrote:I was looking at information on the SNES' GPU and from what I understand most games started out at a resolution 256x224-From there does a television set blow the graphics up to 512x448 to fit into the tv screen? In its basic mode, the SNES sends only even fields every half-frame (for an effective 224p [read: causing clear scanlines on NTSC sets due to the already smaller number of lines of that format. From there, you have a given number of lines depending which format TV you have (PAL/NTSC). Basically the data fed to the TV is synced per screen and per line, so every line is automagically widened (or crushed) to roughly fit the horizontal size of the screen. TVs have a fun thing called analog stretch and sync bursts. Some games use 512x448, but I can't remember any that stay at 256x448, although it's possible. The SNES has independent parameters to 'double' H/V resolution.īase is 256x224 (extendable to 256x239 ), 'hires' doubles H to 512 with the price of major colour bleeding, and 'interlace' doubles V to 448 with the price of half frame rate (extendable to 478).

Snes mainscreen subscreen