TUTORIAL | Cut Lines: Time Remapping in Final Cut Pro, Part 1
Posted Sep 1, 2008

This installment of Cut Lines is Part 1 of a two-part tutorial about Time Remapping in Final Cut Pro (FCP). In Part 1 we’ll take a quick look at Constant Speed Remapping and the mechanics that go into FCP creating it so that you more fully understand why your results look the way they do. My hope is that this understanding will enable you to visualize what the effect will look like before you even apply it, making your workflow faster and your creativity more enhanced.

Next month, in Part 2, we’ll look at all of the tools involved with Variable Speed Remapping and how to use them all together. Again, the goal is to give you the knowledge to visualize not only what your end result will look like but what it will take to achieve that result before you even start your effects work.

Time Remapping is just what it sounds like: remapping the passage of time in a video clip. This can involve making a clip play faster or slower. It can also involve making a clip change from one speed to another, with a ramping up or down of speed throughout the clip.

Time Remapping can be a very useful tool in storytelling. By speeding up or slowing down a clip, or just a section of a clip, or by varying the speed in a complex manner, we can reinforce the mood we’re trying to set. The important thing to remember through all of this, as with any effect, is how the "trick" relates to the "story." Are you using Time Remapping simply to make your video look cool, or does it enhance the emotion of the story being told? Every edit point, every transition, every color grade, every effect, and every note of the music track should contribute to telling the story. A good editor will ask him or herself what every element does to support the story, whether it’s a jump cut, a vignette, or a special effect such as Time Remapping. The point is, as cool as complex Time Remapping can look, it’s not necessarily going to help tell your story. But for those times when it is appropriate (and many event videographers find it a valuable effect and use it often), understanding how it works and how to manipulate it in detail can make the difference between a cheap and cheesy, off-the-cuff look and a professionally polished piece of storytelling.

For example, we may have a shot of a bride during her preparations before the ceremony, as she is turning to face the camera. This shot may be slowed to as slow as 7% of normal speed to reinforce her beauty, and the dramatic emotion of preparing for her wedding ceremony. Of course a little silk stocking effect and vignetting would help accentuate the shot.

In another instance, we may have a shot of the bride tossing her bouquet, and we want to really reinforce the emotional impact of this moment. Not making any cut edit points during our speed changes, we make our clip more polished and keep our viewers’ attention. We’d start with the bride looking at the group of bridesmaids and other women gathering to catch it, then turning her back to them, bending her knees, and bringing her throwing hand down toward the floor. This section would be at twice (200%) normal speed. Then, as her throwing arm comes up to full height we would, in that second of footage, gradually slow her motion down to about a third (33.33%) of normal speed (the ramp down), then hold steady at one-third speed during the toss and catch. Finally, at the moment the bouquet is caught to the moment the receiving hand comes down to its resting position when the act of catching is complete, we’d gradually speed up the clip back to normal (100%) speed (the ramp up). Finally, we’d leave the shot at normal speed for the duration of the clip, showing the other women congratulating the lucky recipient.

This installment of Cut Lines will look at using Final Cut Pro’s often misunderstood Time Remap tools. My goal is to help you understand how to use all of these tools together, making time remapping easier so that you can achieve more polished, professional-looking results quickly.

The Mechanics of Constant Speed
Constant speed changes are the most common, and most of you probably already use them. It refers to the speed of a clip as a whole being sped up or slowed down to one constant speed. For example, to slow a clip down to one-quarter speed, you would right-click (Cmd-click for single-button mice users) on it in the Timeline, select Speed from the pop-up menu that appears, and enter 50 in the Speed field (Figure 1, below).

figure 1

You could also enter a timecode in the Duration field. This would automatically set your speed to force the clip in the Timeline to that duration, keeping the same In and Out points.

Fast motion removes existing frames, so nothing more is needed beyond that, and clarity is not an issue. We take a 1-second clip at 30fps, and speed it up to 200%. Your NLE will need to take out half of those 30 frames to make it into a half-second clip. It’s easy—it takes out every other frame—done. If you speed up more, it makes the proper calculations and takes out the appropriate frames.

Slow-motion effects are a very different story, and things get more complicated. Creating slo-mo clips in postproduction is not going to be as clear and clean as shooting them in-camera. Some cameras allow you to overcrank the footage, just like in a traditional film camera. This gives you clear, clean frames that you actually shot to make up the slo-mo effect. The drawback is that you’re fixed into that single speed change. But doing it in post, with an NLE, the NLE has to create "faked" frames.

The Mechanics of Slo-Mo
Let’s look at the mechanics of slo-mo. Let’s start with a 1-second clip at 30fps that we want to slow down to 50%. FCP (or any other NLE) will take those original 30 frames and space them out evenly across the new 2-second space in the Timeline (1-sec clip @ 50% = 2 sec of Timeline space). This leaves empty spaces in between the original frames that it has to fill up. It does this by creating "faked" frames.

There are two ways for FCP (or any NLE) to do this. One is called Frame Blending. The Frame Blending function tells Final Cut how to make up the "faked" frames it needs to fill in the empty space of a slow-motion clip. Turned off, it will make clear, static frames. The first half of this empty space will use duplicated frames from the first original frame. Then, halfway in between this empty space it needs to fill, it will make the rest of the faked frames from the second original frame (Figure 2, below). This may result in more choppy-looking motion. I say it "may" for reasons I’ll explain in a moment.

figure 1

Frame Blending for Slo-Mo
Turned on, Frame Blending will make frames to fill that new empty space that "blend" frames from each of the original frames. It does exactly as I described before, but this time, it gradually "blends" in—that is, composites in more and more over time—the original frame with the frame from the other end of the empty space (the center of the empty space being a full 50/50 blending of both original frames). Then it blends in less and less of the first original frame until it reaches 100% of the second original frame and 0% of the first original frame (Figure 3, below).

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Which way you use is really a personal choice to be made on a per-clip basis. Depending on the specific movement, contrast, coloring, and edge detail of a specific clip, it may look better with or without Frame Blending. Never assume Frame Blending will look best on all clips!

The other key element of constant speed changes is Reverse. Much like it sounds, Reverse simply allows you to play in reverse motion between the set In and Out points. It’s pretty simple and straightforward.

The Constant Speed "Sandwich" Dilemma
One challenge of Constant Speed changes is when a clip is sandwiched between other clips in a Timeline full of already edited footage. FCP won’t ripple the whole Timeline to allow this, as it could throw audio out of sync quite severely. One trick is to open the clip in the Viewer by double-clicking it, then dropping it into a blank "utility" Sequence (I always have one in every project), do the time change, double-click that again to open the new slo-mo version into the Viewer, reset the In and Out points to match the space in the Timeline to drop it in, or perform an Insert Edit to force it into a larger space in the Timeline. To me, personally, that’s a lot of wasted time and effort. Here’s a workaround I use.

Let’s say you want to slow a clip down to 50% speed. First, if you want this to fit the space the current clip already takes up, zoom in on that clip, place your Playhead on a frame of the clip in the Timeline that would be the middle of what you’d like to end up with. Use the Match Frame function by going to View > Match Frame > Source File (Opt+Cmd+F). This brings up the original source file, not the Master Clip which may already have the In and Out points set. We don’t want In/Out points set in the View. Match Frame also brings up the source clip with the Playhead on the same frame as it is in the Timeline version of this clip.

Next, go to Modify > Speed (Cmd+J) and set the speed to what you want (Figure 4, below).
figure 1

Replace the Clip with the Time-Remapped Version
To position your adjusted clip with the Playhead still in place both in the Viewer and Timeline, press F11 or drag to the Canvas and choose Replace Edit from the pop-up menu (Figure 5, below).

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With this trick, be aware that the placement of the Playhead in both the Timeline and Viewer is critical, and the frames will match back up that way when doing the Replace Edit. Use this approach if you want to slow down a clip and ripple everything else down the Timeline to make room for the additional duration that the slower-speed clip will require.

That should wrap up everything you need to know about Constant-Speed effects. Next month I’ll present Variable-Speed effects in Part 2 of our Time Remapping tutorial. Until then, happy editing!

Ben Balser (benb at bbalser.com) is an Apple Certified Trainer based in New Orleans. He specializes in training and consulting and also produces documentaries, educational material, and commercial work. Contact Ben with Final Cut Studio questions and he will try to address them in future tutorials.