QuickTime Player can’t open movie - The file isn’t compatible with QuickTime Player.

I wonder if this is related to a problem I am having as well... but not iPhone related.

mp4 videos that, when first purchased or received, play just fine in QuickTime Player. But at random lose their icon that reflects the content - to a generic mp4/video icon -and when double-clicked - returns the message that the file contains some media which isn't compatible with QuickTime Player... IF you "continue" -it opens without video -only audio.

Files that have worked a dozen times or more - just suddenly stop working - no modifications to the file - Its as if either QuickTime is confused... or the file is corrupted. But there is no sign of corruption -and other software still opens the files just fine.

This is not a helpful reply. The original poster told you they recorded the video with their iPhone, presumably with the Photos app. This isn't some weird Apple-hostile media format.

I have the exact same problem on Sonoma 14.3 when attempting to trim clips using QuickTime Player using video straight from an iPhone 12 imported via Image Capture.

I shut down and booted up again, opened QuickTime Player only and I was able to save trimmed content from within the app. I then did what I had been doing before, which was to use Handbrake to resize and compress the edited clips. All good. Then, as an experiment, using QuickTime Player, I tried to trim the same original clip and save it. The dreaded: QuickTime Player can’t open movie - The file isn’t compatible with QuickTime Player alert appeared again.

I quit Handbrake and still the problem persisted. My guess is that Handbrake isn't releasing the QuickTime video codecs it accesses for export tasks and so QuickTime Player fails to execute these save/export tasks, as a result. Of course, there may be other applications interfering for different users (for example, Apple Photos) but at least the above scenario is repeatable.

Then again, perhaps Handbrake does release the 'export' codec and that, for some reason, QuickTime Player isn't clever enough to re-establish a connection with these resources. This might not be precisely how these things operate (i.e. codec access), but that's my take.

In short, if you want to avoid this error message:

1. Import using Image Capture to avoid running Photos, which, as a video player itself, could be interfering.
2. Disconnect iPhone and flush out any possible app conflicts by shutting down and booting up the Mac from cold.
3. Only run QuickTime Player.
4. Do your video clip trimming session first, before using other apps that may use video codec resources.

Greetings Koshmariel,

If you are having issues with opening the file, the following information could help:

"Older or specialized audio, video, or image formats might not be supported on your device, or might require different software. 

Apple apps such as Photos, iMovie, Safari, Keynote, and QuickTime Player work with many media formats. Some apps prefer specific formats, but most formats work in most apps without additional software. Older or specialized formats might not work as expected if your device, its operating system, or the app you're using doesn't support the format.

Install all available software updates for your Mac and software updates for your iPhone or iPad. After updating, if you don't have an app that supports the older or specialized media format used by the file, search the internet or App Store for an app that does. If you know the name of the media format, include it in your search.

On Mac, you might be able to identify the media format by selecting the file in the Finder, then pressing Command-I to open an Info window. The format might appear after the label Kind, such as ”Kind: Matroska Video File.” You can also search by the filename extension, which is the letters shown at the end of the file's name, such as .avi, .wmv, or .mkv." If a media file doesn't open or play on your Mac, iPhone, or iPad

We hope this helps!

Sincerely.

It was however helpful to me...