I've been playing around with this to vary degrees of success and I'm getting slightly confused by what I'm seeing (or rather hearing in this case). Just playing the clips in a player like QT or VLC doesn't have any issues, so I know the source files are fine.
I started using Shadowplay recording video at the native resolution of my monitor which is 2560x1600. It offers limited resolution and FPS options like 1080p, 1440p 4K at 30 or 60fps.
All dandy, I started by just using native resolution and 60 fps. But when I imported this into iMovie I was getting audio issues.
In order to get over these issues I just transcoded these files in Handbrake, imported and edited those and exported just fine. I also at this point thought that it was the source resolution that was the issue so I setup shadowplay to use 1080p 60fps thinking that I could then skip the transcoding step, preserve a bit more quality and go straight into the editing.
Seems even these 1080p 60fps source files when imported into iMovie have clicks and pops.
When I check the source files it seems that the FPS isn't 60 but is 59.9729 and the preset I created in Handbrake is a constant 60fps. Could this framerate difference be the source of the audio issue in iMovie?
The source file is 4.6GB but the transcoded file is only 366mb which is obviously a huge difference so I need to check the settings again. But I'm just curious if this framerate difference is the problem.