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How to speed up footage shot in slow motion.

Forum|Forum|7 years ago
October 29, 2018
2 replies
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After Effects CC 2019 Version 16.0.0 Build (235)

The footage I am importing to after effects was shot at 0.10x speed at 60 frames per second. (Artificially 600fps) My goal is to import this footage, speed the clip up to 1.00x speed at 60 frames per second and use frame blending to make the footage look smooth. What is the best way to speed up my footage?

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Correct answer Rick Gerard

Thanks for your reply. To clear some things up, the clip was shot at 60fps. I would like to play this 60fps clip at 600fps in after effects to speed it up (more fps per second will speed it up, right?). How can I do this?

Your logic is common to folks that don't really understand frame rates. You don't want to play the clip at 600 frames per second, you want to speed up time so that one minute of real-time takes only six seconds to playback. You do that by removing frames. Playback is always set in the timeline. The time it takes a clip to play in any given timeline is independent of the timeline frame rate. one second of footage that was shot at 30 frames per second will still take one second to playback even if the timeline frame rate is 50, or 5, or 15.

If you want to change the time that it takes any given clip to playback you have to change the frame rate of the clip. Interpret the clip at a higher frame rate and it plays back in less time. Interpret it at a lower frame rate and it takes longer to playback.

In current versions of AE you can interpret frame rates up to 999 fps. In earlier versions of AE, the maximum interpretation is 99 fps. If you want to make a one-minute clip playback in six seconds you can either interpret the footage at 10 times the frame rate it was shot at or use time remapping and move the last keyframe of the footage back to one-tenth of the original time.

In most cases, when you are speeding up time, there is little need for frame blending. If the math is accurate you won't have any frames to blend anyway so drop your footage in a comp that is an even multiple of the frame rate of the original footage and multiply the frame rate of the original clip by 10.

Did you follow that?

You can also time stretch. Just click on the {} icon at the bottom of the timeline and type 10% in the time stretch dialogue. As long as the timeline is an even multiple of the original frame rate of the clip you will not have any blended frames and the action will look as smooth as it can look. If there are a lot of things moving in the frame, like cars on a highway, and you want to increase motion blur then just add CC Motion Blur to the project. The default settings will give you approximately the same motion blur you would have if you shot a car going 10 mph but you wanted to make it look like it was going 100. You can't get that with frame blending.

I hope this makes things a little clearer. Try creating a new comp from some footage and then just change the file interpolation by selecting the footage in the Project Panel and pressing Alt/Option + Ctrl/Cmnd + g. Multiply the frame rate by 10 and see what happens to the length of the footage.

becomes this:

Ten minutes of original footage becomes one minute in the timeline.

Dave_LaRonde

Inspiring

What's the frame rate of the original footage, and can you get your hands on it? You'll be a lot happier if you can.

robbym50423878Author

Participating Frequently

The original footage was slowed down using another software to .10x times it's regular speed and then recorded at 60 frames per second.

R

Rick Gerard

Community Expert

I am a bit confused, and I think that you don't understand frame rates. if the footage was shot at .10x that that is really meaningless to me. What was the actual frame rate used to shoot the footage? If your target frame rate is 60 frames per second and you shot at 6 frames per second then you have a couple of options. Try and follow this closely.

If the footage was shot at 6 frames per second and you interpret the footage as 6 frames per second then it will take six seconds to playback.

If the footage was shot at 6 frames per second and you interpret the footage (File>Interpret Footage>Main in After Effects) as 60 frames per second then sixty seconds of real-time will take six seconds to playback. Did you follow that? Time will speed up.

If, on the other hand, you had access to a high frame rate camera and you shot at 600 fps and you interpreted the footage as 60 frames per second, one second of real time would take 10 seconds to playback.

Now let me completely confuse you. If your 6 fps or your 60 fps or your 600 fps footage was placed in a 29.97 fps comp or Premiere Pro or any other NLE sequence and the footage was interpreted at the frame rate that was actually used to shoot the footage the footage will all playback in real time. The timeline is pretty close to 30 frames per second so the 60 fps footage would playback almost perfectly every other frame. Frames would be blended because the frame rate of the comp is not evenly divisible by the frame rate of the footage. The same thing goes for the other footage. If you change the timeline (comp) frame rate to 30 then every other frame would be played with from the 60 fps footage, every 20th frame for the 600 fps footage and each frame of the 6 fps footage would be shown 5 times.

Did you follow that?

There is no built-in frame blending or pixel path predicting features built into the time stretching tools in Afte4r effects. The only thing that approaches that is CC force motion blur which will try and look for differences between frames and try and create some kind of motion blur to smooth out the action. It's only when the interpreted frame rate and the frame rate of the timeline are not evenly divisible that frame blending happens. This is true with time-remapping as well as time stretching and AE's other time modifying tools. If every other frame or every 10th frame is played back there is nothing to blend. If each frame is played back exactly 4 times or 5 times, or 100 times, there is nothing for After Effects to blend. You'll need some other software to do that.

If all you want to do is take some footage that was shot at 6 frames per second and speed it up 6 seconds of real-time takes one second to playback just interpret the footage as 60 fps. If you want 12 seconds of real time to playback in 1 second interpret the footage as 30 fps. It's just simple math. If there is some motion that you want to smooth out a bit then try adding CC Force Motion blur and it may help a bit. Frame blending is not going to do much. If you are trying to do something like a hyper-lapse of people walking through Times Square then the best production option would be to set up the camera to take 1 frame every 1/6 or 1/3 of a second and set the shutter speed as close as you can to the interval between shots. I recently did something like this with a .9 second exposure and a 1 frame per second interval. The natural motion blur you get is going to be way more effective than anything you can fake in a compositing app like AE. Simple frame blending is not going to do the trick.

Edit: By the way, there is no such thing as Shot In slow motion. Slow motion footage is shot at a higher than normal frame rate so when it is played back at a normal frame rate the motion is slower than real time. The most common term is over cranking. Fast Motion or under cranked or time lapse footage is shot at a lower than normal frame rate so that the motion is faster when the footage is played back normally. I hopw this helps.

V

Victor Wolansky

Known Participant

if you are speeding up, frame blending will not have much effect in your footage since there will probably not new frames to be created.

you can use that to speed up your footage, although that one I believe is not affected by the frame blending option. or press CTRL+ALT+T to enable time remap on the timeline and adjust the start and end keyframes to achieve the desired speed.

robbym50423878Author

Participating Frequently

Thank you for the reply. Will doing this make my footage look less smooth? After reading this article it suggests to use frame blending to make the clip look smooth and not jerky after applying a time stretch.

Excerpt from Article:

"When you time-stretch or time-remap a layer to a slower frame rate or to a rate lower than the frame rate of its composition, movement can appear jerky. This jerky appearance results because the layer now has fewer frames per second than the composition. Likewise, the same jerky appearance can occur when you time-stretch or time-remap a layer to a frame rate that is faster than the frame rate of its composition. To create smoother motion when you slow down or speed up a layer, use frame blending. Don’t apply frame blending unless the video of a layer has been re-timed—that is, the video is playing at a different frame rate than the frame rate of the source video."

Victor Wolansky

V

Victor Wolansky

Known Participant

That usually applies to slow downs and not to speeds ups, but you can use it anyways, just be sure to press the corresponding switch on the timeline and new frames will be created if needed.

Sent from a Rectangle thing with pretty small keyboard for giant hands. So excuse the typos.

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