Join Ian Robinson for an in-depth discussion in this video Retiming footage with Timewarp, part of After Effects CC Essential Training.
Anytime I think I might have a challenging shot that would be relatively hard to retime, I usually just jump to my effects controls, and in the time area, I apply the time warp effect. Now, before we apply time warp, I want us to look at the footage that we're working with. If you don't already have the board part comp open, go ahead and open it up, and press zero on your keypad to load up a ramp preview. Now, as you can see, we have some snowboarding footage, and it was shot by another person on a snowboard with a handheld camera.
Now, with all the new features inside of after effects, this is definitely a workable piece of footage. I can definitely stabilize this footage and I can apply some retiming results, and create something pretty cool relatively easily. So, let's retime this footage using time warp. I'm going to press the spacebar to stop playback. Now, make sure you have layer one selected. And, I want you to move your current time indicator to three seconds, just before our border gets up to the top of the box. Now, go up under effects, and got to time, and let's apply time warp.
Once we have time warp applied, with time warp applied, let's look at the top options and work our way down. If we look at the method, the method for blending frames together is pixel motion. This is going to give you the best results in terms of detail, but it does require the most processing. If you have footage that has a lot of motion blur already in the image, I would generally recommend using frame mix. If we resize our footage to frame mix, notice how much more sharp the footage actually got.
That's because it's just looking at one frame, and then next frame, and then it's going to blend those frames together. At different points in time, the footage may look better or worse. Like here, it looks worse, because it's a blend of the previous and the next frame. Don't panic when you see stuff like this. In general, if you just watch the footage back in real time using your ram preview, you'll be able to look at it and judge whether or not that amount of shift is acceptable in your shot. I'm going to press the space bar to stop playback here for a second.
Now, I generally use frame mix for footage that has a lot of motion blur in it. Now, if we go to whole frames, this method literally duplicates frames. So, as it slows the footage down, in order to create the additional frames required, it literally duplicates one frame or the next. So, let's see what that looks like. I actually kind of like how that looks. And, as you're looking at the footage, you want to look up in the right corner in the info window, just to make sure that it's playing back in real time. And, I'm going to press the spacebar to stop playback.
Most of the time, when I'm making adjustments in time warp, I'm remapping the footage. I'm having it start and stop at different points, or speed up and slow down. So, when you make adjustments, you can make those adjustments by adjusting the speed keyframe. Now, if I know I'm going to slow down the footage quite a bit, I will generally use the pixel motion method. So, let's go ahead and choose pixel motion. Notice when we choose that option, we get a whole bunch of other options in the filter. You can tune how pixel motion is interpreted.
Before we do that, let's go ahead and make our speed adjustments. I'm going to move my current time indicator to around three seconds. If you notice the next option here is speed. By default, time warp slows the footage down to a speed of 50%. So, if I move my current time indicator to the end of my comp, you'll notice it looks as though my footage has gotten cut off. And, it has, but that's just because time warp is expecting us to bring some of those frames back as we increase the speed of the footage. Let's create a pretty drastic time change.
Move your current time indicator to the start of the composition. And, let's change our speed up to 133. That's 133% it's normal speed. So, we sped it up a little bit. I'm going to go ahead and, and enable that speed change. Now, let's click and scrub in our timeline, and decide exactly where we want to slow down the footage. Let's slow down the footage right around here at 2:16. In order to do that, all we have to do is change our speed parameter. So, let's change the speed down to 50%.
This is the issue of making adjustments by speed. When you change the speed, it actually retimes all the footage before that point in time. So, if we move back a little bit, it's playing at 82% the normal speed. So, it's already started the ramping process. I want this slowdown to happen right about here, before I get to my keyframe just a few frames before. So, what I'll do is, I'll just chain the speed up again to 133 in terms of time.
So now, it's going to play at the same speed until it gets just before where I want it to slow down, and then it's going to slow down. So, we can step through the footage here, and see when she gets just to the other side of the box. Let's say around five seconds. Now, we can add another keyframe. Now, if I click the stopwatch, it'll delete all the keyframes. So, I need to press U on my keyboard, so I can get to my diamond keyframe button here in between my keyframe navigator arrows. Now, we can go ahead and add a second keyframe at the same value of my previous keyframe.
Fifty. Let's move ahead a few frames here, and then we'll increase the speed back up to 133. Now, I know it doesn't look like much has changed, but of course, now this footage is going to speed up and start playing back at 133%. So, let's go back to the beginning of our project and load up a ram preview, and see what happened with the change. I don't know, but I think that looks pretty cool. Now, we could continue tweaking this if we needed to by making adjustments to our motion vectors.
I'm going to press the spacebar here, and just talk to you about motion vectors really quickly. As we scrub through the project here, notice when we get to the slower section, if I zoom into magnification of 100% just by using my scroll wheel here, I can scrub through the image and on occasion you may see that image kind of degrade a little bit. Well, as I scrub through the image, you're seeing the slight blur that's happening around the edge of her body, and that's happening because of the motion vectors. What I would do in general when I'm making adjustments, is keyframe the vector detail.
Now, by default, vector detail is set to 20. Anytime I slow my footage down significantly, like 50% would be a pretty decent slow down, I increase my vector detail. So, here I'm going to move my current time indicator back to my previous keyframe at 133, and I'll add a vector detail keyframe. If you press K on your keyboard to move down to the next keyframe, we can go ahead and crank up the vector detail. I'll crank it up to 100. Just remember, when you crank up the vector detail, it just requires a little bit more processing as you're working through your project.
As I scrub through this part that was in question, I can press page up and page down to go frame by frame. Now, since it's taking a second to load, what I'll do is, just load up the ram preview here, making sure I have from current time selected. And, I'm going to press the spacebar, so I can grab my hand tool and just reposition our snowboarder in the center of the project. Now, again, like I said, increasing the motion vector detail number, is going to increase the processing. So, it may take a second on your system to actually load up those frames.
Now that I have the majority of that loaded in cash, I'm going to press the spacebar and play it back. Now, you can see in slow motion I still have a little bit of that distortion, but it's significantly better. Here, let me reframe here just so you can see it a little more clearly. So, increasing the vector detail has definitely helped increase the quality of our time remap. When the speed speeds back up again, I'd make sure to decrease the vector detail again. Now, there's one more tip I want to give you about tuning motion vectors, and that's the error threshold setting.
If you have noisy footage, you want to decrease the number for error threshold. This will help time warp ignore the extemporaneous motion of that noise. if you have tearing in your footage, you want to increase the error threshold. That'll help increase the blending between the frames, and give you a smoother image. Now, in our example we made adjustments to our time by adjusting the speed. But, by all means, you can adjust the settings according to the source frame as well. I really find that helpful when I know that I need to have a specific frame displayed at a specific point in my timeline.
Now, since that wasn't the case for our example here, I found it made a little more sense just to use speed. But, just in case you decide you ever do want to use source frame, make sure to look in the upper left corner of your timeline, because the secondary number is always going to show you the actual number of the frame that your current time indicator is positioned on.
- Video terminology
- Creating your first composition
- Using layers, masks, blend modes, and track mattes
- Parenting objects
- Building complex objects with Pre-compose
- Exploring the ray-traced 3D renderer
- Understanding the order of effects
- Creating 3D projects from Illustrator files
- Lighting a scene
- Animating type on a path
- Using Keylight for green-screen footage
- Archiving projects