Re: iMovie seems to FREEZE while continue playing added audio.
Unfortunately, it sounds like that particular video file may be corrupted, but I can suggest a few troubleshooting steps to try to determine if it's an issue with the file or with the hardware/software..
First off, echoing Rounik's response to the original poster, how much RAM is installed (>8GB would be better), and what iMovie & OX versions are runningâ€”if it's a brand new MacBook did it come with Catalina (10.15)? Catalina users have reported all sorts of issues with audio and video applications (even with Apple software like Logic), so it could be growing pains..
Apple's troubleshooting checklist includes a number of standard steps, but you might want to try some of the tests below before doing any reinstalling (but definitely do a hard shutdown/restart first if you haven't already).
As to a possible issue with the file itself..
- Try bringing the problem file into a new project for test playbackâ€”sometimes a file may be fine but the project gets corrupted..
- Can you record/playback additional videos without problems? IOW, is the problem specific to that one video file (more likely file corruption) or now that it's happened once does it occur in other video recordings (more likely a sw/hw issue)?
- Can you see the rest of the video file (after the place it freezes) in the timeline? If you stop and cue up after that spot, does the video play ok from later in the file (suggests corruption at that spot in the file)?
- If you can play the later video by manually skipping past the place it freezes, can you edit out that section and achieve smooth playback?
- Is there any effect or transition at or near that spot (in any video or audio track)? If so, try removing them and see if the video plays smoothly through the problem spot
- Can you share/export the file as a QT movie? If so, does it play through the problem spot (more likely an issue with iMovie) or does it freeze at that spot in the exported .mov file as well (more likely file corruption)?
Apple's suggestions are also worth trying, particularly testing with a new library/project, testing in a new (temporary test) User space, and if all else fails, reinstalling iMovie.
If nothing works, and if you can't duplicate the problem with any other video recordings, unfortunately that might point to file corruption. If that turns out to be the case hopefully you can salvage most of the video by editing/exporting the sections that do play properly and piecing together a version that excludes the problem area(s).
Since I don't know what your level of expertise is, I'm including a link (above) to a basic iMovie course, in case you might want to consult it for help in editing/exporting video as part of your troubleshooting..