For certain narrated slide shows and software demos, you sometimes have pauses where your image doesn't change, and other points where changes are happening quickly. If you set your frame rate high enough to capture all the changes, you find that many frames are duplicates--frames that take up precious bytes if you need to conserve space (e.g. if you intend to publish on the web, or want to fit the file on a floppy disk). What you need is to have different frames stay up for a different amount of time.
This week, we'll assume that you're starting with an existing QuickTime movie that has repeat frames in it. This may happen if you record screen actions using a tool such as MotionWorks CameraMan or Strata Instant Replay.You can use ConvertToMovie (available at the QuickTime FAQ software page) to stretch out the duration of frames that are subsequently duplicated, and eliminate the duplicates.
To see your resulting movie, you can open it in MoviePlayer. If you use the step buttons to step through frame-by-frame, you'll see that the playhead jumps forward different amounts for different frames. You should also notice that this new file is smaller than the original.
If you want an even smaller file (and 256 Colors is ok), use ConvertToMovie on the movie in which you just removed the duplicate frames, this time choosing the Graphics compressor and leaving Frames per second blank. You don't have to select "No duplicate differences" this time. (Unfortunately, you can't use the Graphics compressor in the original pass through ConvertToMovie when you eliminate duplicate frames.)
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Judith L. Stern and Robert Lettieri, email@example.com
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