This tutorial guides you through changing a video's playback speed (speeding up or slowing down) using either iMovie or Final Cut. It assumes prior knowledge of the software chosen, but other tutorials on the MDC website or elsewhere may be helpful if you are confused. It was written using iMovie '09 and Final Cut Pro 6, but iMovie '08 and other versions of Final Cut should work similarly.
Note that both methods described below do not specifically change the frame rate, which depends on the project settings and/or the options set when exporting. Instead, one of two things will happen to make the video play at the desired speed: Either a) iMovie or Final Cut will use frame blending to interpolate the individual frames, or b) with the frame blending option turned off, Final Cut will drop or duplicate certain frames (note that iMovie always uses frame blending).
The net result is a more-or-less-noticeable loss of quality, depending on the situation—similar to deinterlacing and many other image and video effects. In general, using frame blending is better than going without, but either way, the altered video will not look as good as the original.
Of the two programs, iMovie is the simpler for this task. With this simplicity comes a lack of control, however, and if there are other issues, you may decide that Final Cut is a better choice. Also, frame blending cannot be turned off in iMovie (see note above).
Importing and creating a project
If you have not already, import your video into iMovie's Event Library (shown in the lower panel by default). If the video is on a camera and not the computer's hard drive, use iMovie's camera import feature (not described here). If the video is on the hard drive but simply not listed in iMovie's Event Library, do the following:
- Under the iMovie menu, select File > Import > Movies...
- Find the desired movie under the file browser, using any import options you find appropriate.
- Click Import.
If you do not already have a project containing the desired clip, do the following:
- Create a project by selecting File > New Project... under the iMovie menu.
- Give the project a name and select the correct aspect ratio (probably Standard 4:3).
- Click Create.
- Select the desired clip in the Events panel (bottom half by default) and drag it into the Project panel (top half by default).
Altering the clip's speed
At this point, you should have a project containing the clip you want to alter. Now, to change the clip's playback speed, do the following:
- Hover the mouse over the desired clip in the project panel and click the actions icon () in the lower corner of the clip's starting point, bringing up the menu as shown in Figure 1.
- Click the "Clip Adjustments" menu item to bring up the panel of the inspector window shown in Figure 2.
- Do one of the following:
- Move the speed slider to increase or decrease the playback speed.
- Enter the desired speed adjustment in the box with the percent sign (%).
- Enter the desired clip length in box below it (which reads 1:40.2 in the figure).
- Click Done.
Once the clip's speed has been altered within the project, you will need to export a movie to get the final result. The following is one simple, flexible way to export your project:
- Under the iMovie menu, select Share > Export using QuickTime..., bringing up the window shown in Figure 3.
- Choose a name for your file and a folder to save it to.
- Click the Export drop-down to choose an appropriate file format. If you are unsure which format to use, here are some hints:
- "DV Stream" is a format used by common consumer tape camcorders (MiniDV and Digital8). It produces extremely large files but is useful if you are dealing with camera footage that you would like to edit later or export back to tape.
- "MPEG-4" is a highly compressed format that produces small files for easy sharing and storage. It makes later editing very difficult, however.
- "QuickTime Movie" is not strictly a format in itself, so it varies widely. If you cannot decide between any of these formats, use this with the default settings, which should be playable on any modern Mac or PC with the free QuickTime Player.
- Click Save and wait while the movie exports. Depending on the format and the length of the clip, it may take some time.
At this point, your movie should be exported at the new speed, and you are finished!
Compared to iMovie, Final Cut is more complicated but offers much finer control. Although it might be overkill for simply changing the speed of a movie clip, knowing how to accomplish this under Final Cut is useful if changing the clip's speed is only part of a larger project involving that program. It is also useful because, unlike iMovie, Final Cut allows us to disable frame blending (see note above), which may be useful in some situations.
Because the program is inherently more advanced, this tutorial will not cover importing or creating a project in Final Cut. The process is not particularly difficult, however, so feel free to experiment or to look for help elsewhere if necessary.
Altering the clip's speed
Assuming you have a Final Cut project prepared with the clip you want to alter placed on the timeline, follow these steps:
- Select the desired clip on the timeline. If you do not select a clip, the next step will alter the rate of every clip on the timeline, which may or may not be desirable.
- Under the Final Cut menu, select Modify > Speed... (or press Cmd + J) to bring up the dialog shown in Figure 4.
- Do one of the following:
- Enter the desired clip length in the Duration box.
- Enter the desired speed adjustment in the Speed box.
- Decide whether or not to use frame blending (see note) and check or uncheck the box accordingly. If unsure, leave the box next to Frame Blending checked.
- Click OK.
Exporting the movie
The process for exporting your clip under Final Cut is virtually identical to the process for iMovie described above. The only difference is that the export command is located under File > Export > Using QuickTime Conversion... in the Final Cut menu.
Once the export is has completed, you should have a new movie that plays at the desired speed, and you are finished!