"TV Pass Fail" NTSC Crosstalk Test

Описание: Tepples' "TV Pass Fail" Test ROM: http://pics.pineight.com/nes/tvpassfa...
NesDev Forum Thread: https://forums.nesdev.com/viewtopic.p...

RetroArch: https://www.libretro.com/
Themaister's NTSC shaders (comes with RetroArch by default, but available separately here as well): https://github.com/OpenEmu/OpenEmu/tr...

I've used this crosstalk test to ensure that the NTSC shaders work in my Unity projects (Thank you Trisibo for porting them for me!), and I figure I might as well show it off here as well, as it is an interesting test. As Tepples describes, "This test relies on the 3:2 exact relationship between NES pixels and NTSC color subcarrier cycles. There are 3 non-transparent colors per tile on an NES; this ROM uses a 3-color pattern to trigger luma/chroma crosstalk."

The reason why it flickers every frame is due to how the NES output video. To summarize it as short as possible: The NES PPU (Picture Processing Unit) generates exactly 8 samples of NTSC signal per pixel, while the wavelength of a chroma signal is 12 samples long, so the colors of adjacent pixels get mixed up to some degree. In addition to this, both the scanline and frame lengths are uneven, so color mixing changes every frame. For a detailed (and more accurate) description, see the article for "NTSC Video" on the NesDev wiki. (In specific, section 6: "Emulating in C++ code")
https://wiki.nesdev.com/w/index.php/N...

Tepples' ROM also features a test for Pixel Aspect Ratio — literally white squares drawn at different ratios to target NTSC and PAL outputs, as well as 1:1 PAR. I haven't featured the test here, but it's also been useful for emulating aspect ratios in Unity.