What are you asking? Do you mean, for e.g. adding slow mo, like putting 60fps footage on a timeline with 30fps footage and rendering the 60 fps retimed (stretched) so your end product is 30fps overall? If so, yes, practically everyone does that at some time, never a problem.

I think he means utilizing variable frame rate, which exists to allow more compression, to create a "look". I think it's a great idea, for example to go from "cinematic" 24fps look to "sports video" 60fps look within the same file. But I don't know of any software that allows one to specify changes in frame rate.

At the end of English football broadcasts they sometimes replay a few highlights with a slower fps look, often accompanied by heavy fx (high contrast etc.). It makes that footage look like it was shot longer ago, and somehow gives it a more epic feel. I guess (as UK TV is 50Hz) they might be dropping alternate fields (or frames) to give 25fps, compared to the 50 fields-or-frames per sec of the live broadcast, but actually it looks even less than 25fps. I don't see how they'd cleanly achieve anything between 10 and 25fps though.

OK, gotcha, thanks. So just capture/convert the VFR to 60 fps, slower frames just get multiplied.

Multiplied but not all frames will receive the same multiplication leading to jerkiness or unique frames and blended frames, which is also a negative as your frames won't look the same. The other method uses optical flow to create new unique interframes but it has to be constantly monitored frame by frame and too time consuming. If you were creating the capture you would never set it to VFR,

There's the other situation with the game it'self constantly changing it's frame rate. I don't know how that works with capture, do you know, can the capture software sync to the VFR of the game?

I don't know if they still do it, but at the Super Bowl here in the states, the halftime show was shot at 24fps and converted in realtime to 29.97. This gave it that filmic frame rate look. I just find it annoying but people consider it "professional". But right now, broadcast and normal video projection does not support vfr within the same video material. But that does not stop it from being shot at different frame rates. You can mix shutter speeds though. "Gladiator" was the first movie that I noticed the action fight scenes had a different look due to shutter speed change.

You know, telecine doesn't hold even a little bit of nostalgia for me.

Neither do audio cassettes, for that matter.

@alifftudm95 @NickHope

Regarding the "epic" look at the end of Football matches. I re-created this look in the middle of a project by using (amongst other things like Vegas Film FX) event UNDERSAMPLE RATE set to something like .8 (or lower?) Can't remember the specifics as it was a long time ago, but I was pleased with the result. Maybe worth a try.

I think he means utilizing variable frame rate, which exists to allow more compression, to create a "look". I think it's a great idea, for example to go from "cinematic" 24fps look to "sports video" 60fps look within the same file. But I don't know of any software that allows one to specify changes in frame rate.

It would be nice to see that kind of films. I think with the technology we currently had right now, its not that possibles.

But a new codecs & system will be required to perform this "VFR Film. Your camera, Software & Display should be able to view changing FPS in 1 timeline.

But bob-h already stated the drawback on "VFR Film", where "not all frames will receive the same multiplication leading to jerkiness"

also might be too jarring for certain people if sudden changes of FPS in the film

Let me explain. Once upon a time compression/bandwidth/space was an issue. So if the action in your video moved at different paces - say you wanted a still to appear for two seconds - if you varied the display from a regular say 24 fps at that point to 1/2 fps you could save a lot of MB. No, it doesn't change the "look". It's not an issue nowadays, just use the 48 frames. If you look at a single frame where the rate change occurred, yes, you might get frame blending at the change, but it's covered by scan and not noticeable to a viewer. It's not like frame blending in Vegas where every frame in a sequence might be blended and you see ghosts. As for sudden changes of frame rate - say where you want to introduce a slow motion sequence, go from footage captured at 120fps to 24 fps, or vice versa - it's been normal for a very long time and viewers (including you) accept it.