If the decimation does anything but average frames, then it's a lossy process and of course there will be detectable differences. And if it does average frames, it's susceptible to the aliasing issues I mentioned above (lighning flashes become gray blurs, etc...)
The question was if there's a single game (or video) you can point me to that (1) has a solid 30Hz frame rate and (2) looks perceptibly "not smooth" for some obvious definition thereof.
Here, I'll give an example that doesn't even rely on high motion, flashing, or other such tricks: a simple video game clip. This particular game engine has its display locked to 60fps: the in-game time between two frames is absolutely constant, so even if your computer is too slow to display in realtime, it will simply output frames slower. As a result, the FRAPS'd capture of the game is a perfect smooth 60fps no matter what.
Additionally, it doesn't have any single-frame effects that would be visually aliased (e.g. lightning), nor does it have any sort of motion blur.
Don't look at the filesizes (obviously, 60fps will be larger), and don't go checking the file info or whatever. Just play them in your favorite media player.
I'm pretty sure you'll be able to tell which is 60fps.
Uh... then why is there a frame rate counter in the bottom right of the screen giving variable numbers between 40-70? :)
I agree that the smaller file looks jumpier. But it's still reporting the same frame rates as the bigger file, which leads me to believe the jumps are an artifact of translation somewhere. Certainly nothing seems to be "locked".
Uh... then why is there a frame rate counter in the bottom right of the screen giving variable numbers between 40-70? :)
Because that's the rate of the frames being displayed during capture. Again, the in-game time between two frames is the same, so if it captures at 50fps, that just means the game runs at 50/60=5/6 times normal speed.
It's similar to how you can capture a 1000fps recording in Counterstrike: the game doesn't actually have to run at 1000fps, it just slows down the game accordingly.
I agree that the smaller file looks jumpier. But it's still reporting the same frame rates as the bigger file, which leads me to believe the jumps are an artifact of translation somewhere. Certainly nothing seems to be "locked".
It sounds like your media player is broken, because ffmpeg gives 60fps for the higher framerate file and 30fps for the lower one.
Yes 30fps has less information than 60fps, but I thought you were saying above that we can't perceive it. The whole point of the argument is that removing every other frame (and thereby doubling the viewing time of the shown frame) is perceptible. A game running at 60fps is doing exactly that: rendering twice as much information and showing it to you.
And it's all relative… The argument is that 30fps is perfectly smooth until you see it side by side with 60fps.
The question was if there's a single game (or video) you can point me to that (1) has a solid 30Hz frame rate and (2) looks perceptibly "not smooth" for some obvious definition thereof.