The Media Extensions feature built into macOS lets you use third-party media formats that aren’t natively supported in Compressor.
Note: The Media Extensions feature requires macOS Sequoia or later.
Download and install the media extension for the third-party media format you want to use.
Choose Apple menu 
Click General in the sidebar, then click Login Items & Extensions (you may need to scroll down).
In the Extensions section, click the Info button next to Media Extensions, turn on any format readers, decoders, or processors for the media extension you installed (you may need to scroll down), then click Done.
Quit Compressor (if it’s open), then reopen Compressor.
You can now work with video encoded in that third-party media format.
Import a video source file that’s encoded in a third-party media format.
Select the imported source file in the batch area.
Tip: Make sure you click the source filename at the top of the job rather than an output row.
If necessary, click the Inspector button 
to reveal the Job inspector.
The Media Extensions section of the Job inspector displays any media extensions that are required to decode media in the selected job.
A green dot indicates that the media extension is being used to decode the selected source media. If a red triangle appears next to the media extension, there’s an issue. Click the Extension Settings button to open the Extensions section in System Settings and resolve the issue.
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