From CatDV 9 Quickstart Manual
Final Cut Pro X
Apple’s new Final Cut Pro X application uses a completely different project format which is incompatible with FCP 6 and 7. With the FCP X 10.0.1 update it is again possible to exchange clips and sequences between CatDV and FCP X, using the new .fcpxml file format which CatDV 9 can read and write.
This provides a way to migrate FCP 7 projects over to FCP X:
Open your project in FCP 7, then export it as XML from FCP 7. (You will need to quit FCP X first. Even though it’s possible to install both versions on the same machine, you can only have one copy of Final Cut Pro running at one time.)
Import the XML file into CatDV. If necessary, check the Extra tracks & sequences option in CatDV’s preferences if you want to bring over more complex sequences (but remember that CatDV only provides very rudimentary cuts-only sequence support).
Select the sequence you want to send over and choose Export as FCP X XML File to save a .fcpxml file
Open this file in FCP X (again, you will have to quit FCP 7 first if it is running on that machine) to create a new project with the timeline.
When exporting an FCP X XML file you can either export a list of clips (to create a new event in the FCP X Event Library) or export a single sequence (to create a new project in the FCP X Project Library, including any clips it depends on in a new event if necessary). You can’t mix events and projects in the same .fcpxml file however. You can also go the other way and export an event or a project as an .fcpxml file from FCP X and import that into CatDV. As well as clips and sequences, metadata in the form of descriptions and timecode markers can be sent across.