Olivier asks, I've seen some GameCube game reviews (on IGN for instance) where they mention frame rates of 60 fps, but that the game does not support progressive scan. Is this possible? I always though that 60 fps and progressive scan were meaning the same thing.
Mike H. Says: Err... so did we. You can't see 60 frames per second on standard definition TV sets, so they ARE essentially one in the same. This would be an IGN boo boo.
Rize Says: This isn't entirely true. F-Zero ran at 60 frames per second on the N64 and that certainly didn't involve progressive scan. This his how a regular TV displays frames (an American or NTSC TV anyway). You get sixty "fields" per second, but each field is not an entire frame. Each field is actually just the odd numbered or even numbered lines. So you get alternating odd and even fields sixty times per second. I'm pretty sure that the game still runs at 60 frames, you just get to see the odd and even lines of each frame instead of the whole thing. This is why you can look closely at a TV and see vertical lines "waving" from left to right as opposed to on a computer monitor where straight lines remain perfectly straight. That said, a game that runs locked at thirty seconds still looks very good, even on a progressive scan TV. The most important way to make a games frame rate look good is to lock it in place (as long as it's 30 and above). When the frame rate swings about wildly is when it's easiest to notice.
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An NTSC television refreshes at 60Hz (think of this as a "pulse" of the picture guns), interlaced. Every half a second, you see one FIELD of picture data. However, these fields are interlaced, meaning that it skips a line. The remainder of that second, the screen displays the other lines. It happens so fast, that your brain blurs it all together to make one solid picture.
This "solid" picture that you see every second is a FRAME. A game running at 30 FRAMES per second is displaying the same FIELD twice every second.
In F-Zero for N64, the game ran at 60 FIELDS per second. Every interlaced field had new picture data in it, and this creates a very smooth feeling to the motion. Again, your brain blurs all of these interlaces fields together, and it seems very smooth and responsive. It's particularly effective with low-resolution N64 games because it's not trying to take advantage of the full screen resolution of a TV screen (which is approximately 640x480), most N64 games ran at 320x240. Since it's only half the vertical resolution, this introduces no flicker.
Flicker in games running at 60 FIELDS per second on a standard TV occurs because they are running at high-resolution 640x480, so you are only seeing half of the picture data that you could be seeing every half second. This creates a noticeable flicker, which is apparent in games like Luigi's Mansion and Super Smash Bros. Melee. There are ways to mitigate this flickering effect, and SSBM uses one such method.
On a progressive scan (HDTV), the picture isn't interlaced. Every half a second, you see the entire FIELD of picture data. Games that can run in progressive scan mode do not flicker, because it's the interlacing combined with those two interlaced pictures being different that causes flicker.
Thus, only a game running in progressive scan mode is capable of running at 60 FRAMES per second. All interlaced games run at 60 FIELDS per second. This is why you can't use the term FPS when talking about console games. No one would know if you're talking about Fields or Frames (although we could probably figure it out).
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It's true that you can only truly see 60 frames (or fields or whatever, Rick can correct me) per second in progressive scan, but 60 fps (gasp!) in interlaced mode still looks better and smoother than 30 fps in interlaced mode. That's why F-Zero X looks smoother than any 30 fps game on the N64, even though the N64 doesn't support progressive scan at all.
