What happens to the frames when you export 60fps at 30fps?

[Tiggsy]

Sorry if its a dumb question - if I drop a 60 fps clip into my editor and then export it to a finished film at 30fps - what happens to the extra frames? Does it just drop every other one???

[SCEtoAUX]

Tiggsy said:

Sorry if its a dumb question - if I drop a 60 fps clip into my editor and then export it to a finished film at 30fps - what happens to the extra frames? Does it just drop every other one???

Well there will be normally be some kind of options that pop up when dropping a clip into a sequence where the frame rate isn't the same as that of a source.

One option will be, as you've mentioned, that frames will be dropped. Every other frame for going from 60 to 30 fps resulting in the clip replaying at the correct speed but with a reduced temporal resolution (fewer frames over time than it originally had).

Another option is that frames aren't dropped, meaning that your clip still replays at 30 fps in the final output, but only at half speed. (And therefore only half of the chosen clip gets used. (Again, temporal resolution is reduced but by losing a bunch of frames from the end of the clip rather than by losing every other one within it).

There will be other options, such as blending frames together so that two original frames combine to make one new one, and normally you would want something that kept speed correct, but not always.

As a side note, what you're asking is related to how broadcasters produce such amazing slow motion replays these days. Shoot something at a high frame rate (typically 100-200 frames per second) and then play it back at the UK standard of 25 frames per second. The result is a lovely smooth replay.

[Tiggsy]

Ok - makes sense.

I get the high FPS -- I shoot at 120 a lot on my go pro 6 and drop it down to 30 for play back. But when I then drop a 60 fps clip into the time line I just wondered where the extra frame go as playback is in "real" time.

Maybe as I use Filmora (super simple software) it just works that out for me!


Just a thought - when I slow 120 down to 30 - or just shoot in 30 to start with (as I do when using 2.7k or 4k) and then export it at 60fps - does it just use 2 identical frames for each 60th? As it cant have enough FPS to go round!

[Fordo]

Tiggsy said:

Ok - makes sense.

I get the high FPS -- I shoot at 120 a lot on my go pro 6 and drop it down to 30 for play back. But when I then drop a 60 fps clip into the time line I just wondered where the extra frame go as playback is in "real" time.

Maybe as I use Filmora (super simple software) it just works that out for me!


Just a thought - when I slow 120 down to 30 - or just shoot in 30 to start with (as I do when using 2.7k or 4k) and then export it at 60fps - does it just use 2 identical frames for each 60th? As it cant have enough FPS to go round!

Why would you want to export 30fps footage, as 60fps? It will either double up on frames as you mention. (in which case, it will still look exactly like 30fps footage, only you've doubled your file size for no reason). There may be the options in the software for it to do more funky things - like frame blending. Where every other frame will be a blend of the two real frames either side. (which generally leads to a blurry looking mess. And there is some clever stuff called optical flow, where the software analyses dominant motion in the frame and literally tries to 'make' the additional frames. However, it doesn't really work a lot of the time, as it's just guessing / and warping the image about to make frames that aren't there. It can work when its a simple shot - say a person jumping against a blue sky, as its really easy for the software to work out whats background, and whats a moving object. But in a complex image, it often has no idea whats really what, and makes a warped horrible mess that just looks wrong. (theres actually fake slow mo software, twixtor, that was all the rage a while ago, that uses this tech)

But as per your original question - yup, if you drop a straight 60fps clip onto a 30fps timeline, it'll just ditch every other frame, unless you tell it to conform the footage to 30, in which case it won't ditch any frames and the footage will be at half speed on your 30fps timeline

Phew, thats a lot of geekery, hope that helps

[Tiggsy]

yep - very useful. Thanks!