FCP 7: Create a Variable Speed Clip

[ This article was first published in the November, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]

 

Michael Grenadier sent in a request a while back asking me to create a tutorial that shows how to create a variable speed clip.

There are two ways you can create a variable speed clip: in the Viewer or in the Timeline. The Viewer is easier, but the Timeline is more accurate.

First, though, before we start, here are four rules to keep in mind about creating a variable speed clip.

Creating a variable speed clip:

1. Changes only the video, not the audio, of the clip
2. Does not change the duration of the clip.
3. Does not change the duration of the sequence.
4. Is guaranteed to play the In, after that, all bets are off.

Contrast those four rules with what happens when you make a constant speed change to a clip.

Creating a constant speed clip:

1. Changes both the audio and video in the clip
2. Plays every frame from the In to the Out.
3. Changes the duration of the clip.
4. Changes the duration of the timeline.

VIEWER VERSION

Ken Stone was the one that showed this to me and it made so much sense that I’ve been introducing the concept this way ever since.

Here are the steps:
1. Edit the clip who’s speed you want to change into the Timeline so it is the length and position you want.

2. Double-click the clip to load it into the Viewer.

3. Click the Motion tab, then, go down to the bottom and twirl down the right pointing triangle next to Time Remap.

4. Although the numbers on the left look very impressive, you can ignore them – we are concentrating on the green line to the right. If you can’t see it, grab the lower right corner of the Viewer and drag it to the right to expand the size of the window until you can.

5. A helpful keyboard shortcut is to type Shift+Z. This expands, or contracts, the clip (represented by the light gray portion of the window) to fit in the window.

6. The green line represents the speed of your clip. What the angle is does not matter. That it HAS an angle is critical. As long as the angle of this line does not change, the speed of the clip does not change.

7. Select the pen tool (press P) and create, for this example, four keyframe along the line. You can create any arbitrary number of keyframes — my goal here is to show you how this works. You can then apply this technique in an almost unlimited number of ways.

8. Here’s how to change the speed of the clip. Adjust the keyframes so that:

• the first line segment remains untouched
• the second line segment declines a bit
• the third line segment is flat
• the fourth line segment goes down-hill right
• the fifth line segment has a steeper up angle than the first line segment.

9. Here’s how to translate the line angles into speeds:

• If the angle of the line doesn’t change, the speed doesn’t change.
• If the angle of the line is shallower than the original angle, the clip slows down.
• If the angle of the line is flat, the clip becomes a still frame.
• If the angle of the line goes downhill right, the clip goes in reverse. The speed it goes in reverse depends upon the steepness of the line.
• If the angle of the line is steeper than the original angle, the clip goes faster than original speed, the speed being determined by the steepness of the line.

Take a minute and try it.

Extra credit: Control+click any keyframe and select Smooth. This adds a Beziér control point that allows the speed change to occur gradually, rather than abruptly.

 

 

The nice thing about changing speed in the Viewer is that it is easy to see your changes as you drag the green line up and down.

TIMELINE VERSION

What working in the Viewer doesn’t allow is changing the speed with any precision. THAT requires doing speed changes in the Timeline using time keyframes. When ever you work with keyframes, you must use at least two — one to indicate the start of the time change, the other to indicate where the time change ends. So, we will create a simple variable speed change where the clip starts at normal speed, then switches to 50% slow motion in the middle of the clip.

Here’s how.
1. Edit the clip who’s speed you want to change into the Timeline.

2. From the tool palette, select the Time Remap tool (press SSS).

3. In the middle of the clip where you want the speed change to start, click to set a keyframe. BE SURE not to move the mouse once you click the mouse. In this case, I added a keyframe in the middle of the clip.

4. Go to the point where you want the speed change to either end or change speed, and click to set a second keyframe. HOWEVER, this time, don’t let go of your mouse. Drag your mouse and watch the yellow tool tip.

As you drag your mouse, the speed of the clip to the left and right of the keyframe will change. Depending upon how many frames you have between the two keyframes, you may not be able to get perfectly round numbers (i.e. 50%, 200%) but you can get close.

Load the clip into the Viewer and notice how the Time Remap tool has added keyframes, but this time, you’ve done it with a precision that allows you to control the speed of the clip before and after the keyframe.

To reset all your settings back to normal, click the red X in a circle next to the Time Remap title in the Viewer.

Whether you create your keyframes in the Viewer or the Timeline, you can always add Beziér curves to any keyframe, once its been created, by control+clicking a keyframe in the Viewer.

Note: Not all speed changes will look great – it depends upon how many frames you have and what speed you’ve chosen. Also, pulldown frames, added when converting 24 fps material at 30 fps, will always make slow-motion look stuttery.

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