Ability to both use Green Screen and then resize the clip?

You are right you can only use green screen or PIP but not both. That said, iMovie supports pre-keyed footage. Essentially certain codecs support transparency (e.g. ProRes4444). You can achieve the desired effect in two steps as others have mentioned by first creating the pre-keyed video then re-importing it for use with the PIP feature. There are several expensive apps (Apple Motion or Final Cut Pro) that can save out pre-keyed footage but if you had those, you wouldn't be using iMovie. I figured out you can do this for free using the slightly older iMovie 9.x.x. I believe you can still download it from Apple here. The trick to get an existing video that is completely transparent (i.e. ProRes4444). It doesn't matter how long the video is as you can extend it using the "Add Freeze Frame" feature. Add your green screen footage on top of the transparent movie and then export using Quicktime to a ProRes4444 movie. Make sure you use the Millions of Colors+ option. Once you create that, re-import into iMovie 10 and use it in the PIP function. I did this successfully today after a lot of experimentation so wanted to pass on the trick!

The workaround is to do it in two steps.

First, create your green screen clip in a scratch project. Output (Share) to a file.

Re-import it to iMovie, add it to your project as a PIP.

Matt

So the buffalo are the background you want to use in the green screen clip. OK I got it now.

You're right, what I describe will not work.

You're not going to be able to do it with iMovie alone.

You'd need to use something like Motion or After Effects to essentially cut out the green screen background and replace it with alpha channel that will be transparent when you use it a PIP in iMovie.

FinalCut Pro X might be able to do it as well (I know it can with white or black backgrounds).

Matt

Wow. Good answer!

You can disregard my suggestions.

I'll keep your tip in mind.

So you can use iMove to generate the clip with an Alpha Channel.

Matt

Tom

I did everything up to 3 and when doing 4, saving the file - how did you do that? Share to File? I ended up with Zero bytes! So can't reimport.

Any advice would be helpful.

Thanks

Ed

Sorry ignore this.

Am nearly there...

Good idea. I just tried this, but when I re-imported the video it just remained black over top of the other video. The black wasn't really transparent. It seems to have saved it as black pixels ? Any thoughts ? Is this a setting in the export dialog that I'm missing ? Thanks everyone.