Is 40 fps possible in NTSC standard?

[Supasso]

Since we can display 24 fps movies in 60 hz NTSC by using 3:2 pull down -- the first frame display in the first 3 fields, second frame display in the next 2 fields, third frame in the next 3 fields, and so on -- could we display 40 fps on a 60 hz NTSC by using 2:1 pull down? -- displaying the first frame in first two fields, second frame in the next field, third frame in the next two fields, and so on, resulting in 40 unique frames of animation per second in the period of 60 fields.

Is this possible?

 

[Thowllly]

Strange question, me thinks. You are of course free to display any frame however long you want.

 

[maskrider]

I suppose a console will try to output at 60Hz (or 30Hz full frame) whenever it is possible, if it cannot output at 60Hz, it means it is stalling and have to repeat the current frame at the output.

I think there is no need to define a scheme for some fps rate as at those times the console is stalling and the CRT/output controller is forced to repeat whatever is in its frame buffer.

And for the 40fps question, you can do whatever you want at the output for sure, but I think the scheme may results in jumpy feeling during motion.

 

[Supasso]

I should have been more clear. I mean if it's possible for games to run at constant 40 fps framerates.

Will it make the game smoother than 30 fps one, or just wierd jumpy framerates? If it makes games smoother, it would be a nice compromising between 30 and 60 fps.

The reason I'm asking because I suspect that some games actually run at that framerate. Zelda WW looks smoother than 30 fps, but it obviously not 60 fps. Maybe it's just my perception decieving me. Sonic Advanture was the other game that looks smoother than 30, but it's definitely not 60.

Also I heard that when a 60 fps game slows down, it jumps from 60 to 30, but Starfox Adventure, which runs at 60 fps, does not look like that, when slows down.

 

[Thowllly]

Ah, ok, now I get it.

Will it make the game smoother than 30 fps one, or just wierd jumpy framerates?

That's an interesting question. To find out, I made two little programs for the C64 that scrolled the screen. The first ran at 30fps, displaying each frame twice before scrolling. The second ran at 40fps, alternating between showing each frame once and twice, as you described.

My personal impression is that the one scrolling at 30fps felt smoother than the one scrolling at 40fps. Of course, this was a 2d test; it might feel different in 3d games.

 

[Supasso]

Thanks, Thowllly. I wish I could try it myself like you just did.

 

[Thowllly]

I wish I could try it myself like you just did.

If you have a C64 emulator, you can try it yourself. Download it here. Load the program into the C64 with

LOAD "C64SCROLLER.PRG",8,1

and then type

SYS 3000

to start it. Then follow the onscreen instructions. The difference between the two 40fps modes is that one always scrolls 3 pixels each update, while the other scrolls 2 pixels, waits 2 frames, scrolls 4 pixels, waits 1 frame, scrolls 2 pixels, and so on.

Using a real C64 would of course give the best results, but if you use an emulator you should set your screen refresh to 60 or 120Hz if you emulate an NTSC C64, or 100Hz (or 50 or 150Hz, if you can) for a PAL C64. If you get stuttering, the synchronisation between the emulator updates and the screen updates is not right. Try one of the other c64/screen refresh combinations if that happens. Or you can try tweaking the screen refresh with Powerstrip, if you're willing to go that far

 

[Tagrineth]

Yes, perceived frame rate will always be different for 2D vs. 3D.