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>>Firstly, on a home console there are just two playable frame rates: 30 fps and 60 fps. This is probably very basic but I am going to ask anyway: why are 40fp

>>Firstly, on a home console there are just two playable frame rates: 30 fps and 60 fps. This is probably very basic but I am going to ask anyway: why are 40fps, 45fps or 47fps not possible?

NickPollard 11y ago
Because the display is normally running at 60hz, so if you don't want tearing (where the frame to be displayed changes halfway through monitor refresh, leading to a sharp tear across the screen), you need to run at an integer number of refreshes per frame (known as vsync). 1 = 60fps, 2 = 30fps, 3 = 20fps.
pandaman 11y ago
The video out is fixed at 60hz so, at constant framerate, you can only output every frame, every two frames, every three frames etc. In other words you framerate is a factor of 60. You could tripple buffer and do variable rate so an average could be something like 40, but it would cost you 8M and variable framerate is perceived worse than constant. If you cannot hit 60 you better spend more time on getting game prettier at 30 than waste memory on a tripple buffer and get a stuttering game as a result. On current gen memory is not as much an issue but the variable framerate is still not perceived well.
MaulingMonkey 11y ago
Because your monitor is (probably) refreshing at 60hz. Your frames will display for some integer number of monitor refreshes - at 1 you'll get 60fps, at 2 you'll get 30fps. Over a second, it's of course entirely possible to get something in-between, where some frames are displayed for 1 refresh, and others for 2 refreshes. Inconsistently waffling between these is going to be more jarring than sticking to one. Recently, you have things like nVidia's... gsync? Which make the monitor refresh rate variable with compatible monitors, to match the game framerate, making 45fps entirely possible, and reducing the jarring from varying frame lengths. But this recent, rare, and likely PC and/or GPU vendor specific still.
jharsman 11y ago
Traditionally TVs only support 60 Hz refresh rates (or 50 Hz for older PAL sets), so you either render a new frame for each frame the TV can refresh, or you display a frame for two TV refreshes. Thi sisn't strictly true any more, since many TVs now support 72 Hz (to be able to display 24 fps content like film), but my guess is that doesn't have wide enough support to rely on.

>>Firstly, on a home console there are just two playable frame rates: 30 fps and 60 fps. This is probably very basic but I am going to ask anyway: why are 40fps, 45fps or 47fps not possible?

NickPollard 11y ago

Because the display is normally running at 60hz, so if you don't want tearing (where the frame to be displayed changes halfway through monitor refresh, leading to a sharp tear across the screen), you need to run at an integer number of refreshes per frame (known as vsync). 1 = 60fps, 2 = 30fps, 3 = 20fps.

pandaman 11y ago

The video out is fixed at 60hz so, at constant framerate, you can only output every frame, every two frames, every three frames etc. In other words you framerate is a factor of 60. You could tripple buffer and do variable rate so an average could be something like 40, but it would cost you 8M and variable framerate is perceived worse than constant. If you cannot hit 60 you better spend more time on getting game prettier at 30 than waste memory on a tripple buffer and get a stuttering game as a result. On current gen memory is not as much an issue but the variable framerate is still not perceived well.

MaulingMonkey 11y ago

Because your monitor is (probably) refreshing at 60hz. Your frames will display for some integer number of monitor refreshes - at 1 you'll get 60fps, at 2 you'll get 30fps. Over a second, it's of course entirely possible to get something in-between, where some frames are displayed for 1 refresh, and others for 2 refreshes. Inconsistently waffling between these is going to be more jarring than sticking to one. Recently, you have things like nVidia's... gsync? Which make the monitor refresh rate variable with compatible monitors, to match the game framerate, making 45fps entirely possible, and reducing the jarring from varying frame lengths. But this recent, rare, and likely PC and/or GPU vendor specific still.

jharsman 11y ago

Traditionally TVs only support 60 Hz refresh rates (or 50 Hz for older PAL sets), so you either render a new frame for each frame the TV can refresh, or you display a frame for two TV refreshes. Thi sisn't strictly true any more, since many TVs now support 72 Hz (to be able to display 24 fps content like film), but my guess is that doesn't have wide enough support to rely on.