avi file play in I movie

The avi format is a legacy format that will not play in iMovie running on Catalina or Big Sur.

However, I believe that you can convert it to H.264, Mp4/AAC with the free download Handbrake, and that will play in iMovie.

You can get Handbrake here:

https://handbrake.fr/

A simple way to do it is to open Handbrake and do a File/Open Source. Navigate to your video and choose it as the source from the resulting screen. Then do File/Start Encoding. Wait a couple of minutes for the conversion to complete. Then save and import the converted clip into iMovie.

-- Rich

I've not used Compressor or Final cut Pro X, but any conversion app that can convert .avi to H.264, Mp4/AAC should work.

-- Rich