I did all my editing in Final Cut Pro X with Resolve handling the color correction. All the variable speed changes I applied in Final Cut Pro X show up in Resolve without issue. The issue becomes when I render out to import back into Final Cut Pro X. What should be going at a faster speed plays back in real time in the Deliver page. Once the XML is imported into Final Cut the grade comes over fine but what should be playing back at a faster speed plays back in real time. I am guessing I should do speed changes in Final Cut Pro X after color grading in Resolve. Any advice is greatly appreciated. My guess the issue is on the Resolve side of the equation.
Retiming as well as "conformed" speeds are always an issue with roundtrips. Generally it is recommended to strip out all speed changes before you send the timeline to Resolve and then rebuild on the back end. Are these straight speed changes (e.g. the entire clip at 59%) or ramped?
My guess is that's part of the problem. Constant speeds would likely have passed through the roundtrip just fine. At this stage, to my knowledge, no two applications will interpret variable speed information in the same way.
[David Mathis]"What should be going at a faster speed plays back in real time in the Deliver page. "
This is because Resolve will render all the frames of the clip, not just the result frames of the speed change. This allows you to rebuild the speed change back in FCPX if needed using all the selected frames.
I find that speed changes, even variable ones, hold up remarkably well going from FCPX to Resolve, but I have not moved to v14 beta so maybe that's the difference?
You could also bake the speed changes (export/import/edit to timeline -> Send to Resolve).
Another thing I have done in the past (to get rid of Resolve's compound clips) is to rebuild the speed change in Resolve.
It's more of a pain in the rear, but it does work.
Lay a new version on the clip on top, remake the speed change (unfortunately, copy/paste variable speed changes does not work, at least not in v12.5). Delete the older clip. Render and send back to FCPX.