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How to overlay translucent movie in iMovie.
It's sad that iMovie don't have such function. iMovie can only overlay movies but cannot make the top movie translucent.
But if your purpose is to overlay a translucent logo or animation text or images in a movie, then you may use Keynote to create a ppt animated slide and make the background to transparent.
Step 1. Click slide background and set it to "No Fill" on right hand side bar.
Step 2. Create the content you need.
Step 3. Save it in this way. (IMPORTANT!)
Click File -> Export to Movie.
Must check "Custom" in resolution and check "Apple ProRes 4444". Then you'll get a movie with transparent background.
Now insert it into your iMovie and see.
