Video Compression

Yes, you would need to vary the speed of the sound as well ... or delete out parts that are not specifically synced to the video. When you control-click on an audio or video clip, and choose Show Speed Editor from the pop up menu, a speed editor slider handle will appear in the upper right hand corner of the clip. Slide to the left to speed up the clip. Slide to the right to slow down a clip. You can also split clips into segments and vary the speed of the segment without affecting the speed of the remainder of the clip. Also, there is a "preserve pitch" setting in the controls that are revealed when one clicks on the speed icon (the one that looks like a little clock)in the toolbar at the upper right of the screen.

Another thing: If you export out the project as is, and then import it back into a new iMovie project, you can vary the speed of the entire movie, or segments of it, to shorten it. The way the sound will remain in sync.

-- Rich

Try using the speed control to speed up some of the clips where it won’t make a significant difference to the overall display. Make a duplicate of the project first, and work with the duplicate so as to preserve your original.

Exporting the project and opening it in QuickTimePlayer will not affect the duration. You have got to either change the speed or remove some media.

— Rich

Video editors like iMovie are not intended to string a load of clips together.

The clue is in the name "editor" . . . they are designed to let you select the interesting parts from what has been shot.

Most amateur films that I have watched which lasted over 20 minutes have been excruciatingly boring to everyone except the creator . . . I have also come across 2 minute films that have seemed to take an age to finish!

A skilled editor could cut down a 2 hour bunch of clips to around 10 minutes or less without losing any information and in the process create a dynamic film which audiences would enjoy watching.