Transcode incompatible media
As part of the transition from 32-bit to 64-bit technology in macOS, macOS Mojave is the last version of macOS that includes support for video formats that rely on QuickTime 7. If you have media files that rely on QuickTime 7, you can use Compressor to transcode the files to a format compatible with versions of macOS after macOS Mojave.
Media files and settings that are incompatible with versions of macOS after macOS Mojave appear with an alert in the Job inspector.
Important: To ensure future compatibility, make sure to transcode the files before you upgrade to the next major version of macOS after macOS Mojave. After you upgrade, the option to transcode incompatible media will no longer be available.
For information about media formats affected by the transition to 64-bit technology, as well as media formats compatible with versions of macOS after macOS Mojave, see the Apple Support article About incompatible media in Final Cut Pro X.