problems with iMovie 10.3

Thanks for all that great data.

You are correct that not all Mp4 files work in iMovie. It must be Mp4/AAC. AAC stands for Advanced Audio Coding.

If you have time and can do a little more experimenting per below, and post back with your findings, it may help us to track down the problem.

Your original clip has the letters HE in the codec. That might be short for HEVC, High Efficiency Video Codec. The exported clip does not contain the letters HE. Perhaps HE, if it means HEVC, is what is causing the problem. Put your original clip into QuickTimePlayer and do a Window/Show Movie Inspector. Does it show the format as HEVC? If it were recorded in HEVC, you can export it out from your iPhone and eliminate the HEVC by going to Settings>Photos>Transfer to Mac or PC and disabling "Keep Originals". Then export the clip. If you try that, see if the exported clip will work in iMovie.

Another thing you can do is try converting the troublesome clip to H.264, Mp4/AAC with the free download, Handbrake. Do that even if the codec already is indicated to be Mp4/AAC. Re-rendering often cures issues.

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. Then see if the converted clip exports normally in iMovie.

Another experiment that you might try is to import your original clip into iMovie and do a Modify/Detach Audio. Then delete the audio and export out only the video. If the video-only exports quickly that would indicate that the problem is with the audio codec.

-- Rich

If by chance you are exporting at Best Quality (pro res) that can slow down export time by 4x. Pro res is a very high bitrate setting and is not needed unless one is going to do very technical professional editing.

Lack of application space for iMovie to run efficiently can also cause slow exporting.

Then, possibly, your system just needs a little tweaking after the updates. Try these two procedures, that are easy to do and and simply involve rebooting while holding down certain keys:

Try resetting the System Management Controller (but no longer available for the new M1 computers):

https://support.apple.com/en-us/HT201295

Resetting the NVRAM or PRAM

Try resetting the NVRAM or PRAM:

https://support.apple.com/en-us/HT204063

The above may cure the delay in sound, although I'm not quite sure what you mean when you say that the "audio takes forever to appear". Sometimes Mp3 audio can cause some problems, so if you are using Mp3 you might consider changing the audio codec to AAC or AIFF.

-- Rich

-- Rich

Looks like we reached the same place by different routes. Converting the clip seems to be the workaround. I agree completely that no one should have to do a workaround to make iMovie work. Hopefully Apple will fix the problem.

You can give feedback directly to Apple at this link:

https://www.apple.com/feedback/imovie.html

I am still curious as to whether the original clip was in HEVC format. No sure what the "HE" means. Could you by any chance open the original clip in QuickTimePlayer and do a Windows/Show Movie Inspector? That would reveal whether the clip is in HEVC format.

Thanks, and glad that you found a workaround.

-- Rich

I have the same problem as of today.

The audio of my video takes forever to PROCESS.

I see the full video, but the audio underneath just has the loading (as seen on screenshot) for hours and does not want to load.

How can I or can Apple fix that?

I'm not running iMovie 10.3, so can't comment there.

Sometimes with an update preferences get corrupted or changed. Try deleting preferences. Open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

-- Rich

Ah. So, HE AAC is intended for streaming whereas AAC is for higher quality. Apparently HE has a different algorithm. As I mentioned before, iMovie likes Mp4/AAC. Possibly the algorithm for HE AAC might not be compatible with iMovie, and that might what caused the problem. When you re-encoded, the HE was eliminated and you were able to export at normal duration. Just my speculation, of course.

Thanks for taking the trouble to post the data.

-- Rich

Hi all, I've had the same problem for weeks and even bought a new Macbook, thinking that this was a hardware problem (I've been planning to get a new one anyway, but this definitely speeded up my decision :D). As you could expect, that didn't help. But your solutions have worked for me. Thank you!

I have similar problem. It updated, saying optimisations for Apple Silicon. I thought it would work faster than before. But the render/export times have got worse. I used to make short family videos, 10-15 mins longs. And it would take 5 mins to render in 4K. Now it says oner 3 hours. What went wrong? The videos were shot on iPhone so I trust its nothing to do with incorrect codec or something similar. Apple should understand those files very well.