How to make picture in picture video semi transparent?

Question

I do know how to make picture in picture semi transparent if I import a photo instead of a video. However, if I import an video and want that video to be semi transparent at the right top cornor, I can do so with imovie? I know I can make the second video semi transparent if I use cutaway instead of picture in picture. However, I do not want the second video fill the whole screen, just the right cornor of the whole video.
Please reply if you know how to do it in imovie. Thank you

Answer 1

renaixbf wrote:
...  video to be semi transparent at the right top cornor, …  I can make the second video semi transparent if I use cutaway ...  I do not want the second video fill the whole screen, just the right cornor of the whole video.
your wording confuses me ... what exactly do you want to accomplish:
a cut-away replaces video, but keeps audio - that has nothing to do with 'transparency' (??)
for sure, you can place and resize a PiP anywhere on the screen (pic#1)
or, do you mean by 'semi-transparent' keying a PiP? (pic#2) A color-key within a PiP is not optional in iMovie; although, I tested it: if your source video contains 'alpha transparency', iMovie support that either.
https://sites.google.com/site/karstenschluter/im09-counter
or, do you want to manually change the compositing mode (pic#3)? That, indeed is not optional in iMovie.
or, did you mean by 'just a part' cropping a PiP/second layer (pic#4)? Again, not optional in iMovie, complex compositing effects are habitat of professional tools such as FCPX.