The standard dimensions of the NES video output (256x240) are of course well known. Brad Taylor's documentation does an excellent job of describing what the PPU is doing during this time, and Blargg's NTSC filter creates artifacts very close to those seen on the real system. (About all that is needed now is a PAL artifact filter for European games.)
What is not quite as clear to me is what is displayed outside the active screen area. If the horizontal position and/or vertical hold control on a TV set is adjusted, it's possible to see portions of the screen that were never intended to be viewed, such as the color burst and blanking intervals. These follow a predictable pattern. On the Sega Master System, this has been documented by Charles MacDonald. Does anyone know how this works on the NES? This information could be useful if someone wanted to implement positional or hold controls as part of their TV emulation.
Overscan emulation
Moderator: Moderators
From the wiki page:
Sync is below black level, so would appear as black. Colorburst is like color $18 (maybe $28, but definitely that hue). Pulse is a mid-gray.
Code: Select all
25 sync
4 black
15 colorburst
5 black
1 pulse
15 left border (background color)
256 active
11 right border (background color)
9 black