I only just recently cut a project on FCPX that I wanted to grade in Resolve. As I did some tests with the roundtrip before, I thought it ought to wok and it did, albeit with some quirks.
First, I found out that Resolve can't handle - even constant - speed changes made in FCPX that have quality set to OPTICAL FLOW, so I removed it on every shot and brought the XML into Resolve. That kinda sucks, but is understandable in a way. Timecode is freaked-up by Optical Flow, I guess.
When I was finished grading I rendered to ProRes files with a 50 frames handle-lenght. When I exported DaVinci's XML back into FCPX everything conformed ok, save the speed-changed clips. Firstly the speed-change was removed. What's worse is that all the new (DaVinci rendered) clips that had originally a speed-chande applied to them were in the timeline starting with the first frame of the rendered clip (Which had a 100 extra frames 50 before and 50 after the original IN- and OUT point). So I had to manually slip each clip 50 frames to the left, reapply the speed-change and cut off the rest to the right after the OUT-point.
Is this normal behavior, or do I do something wrong? Should not DaVinci reapply the 50% (or whatever) constant-speed-change into it's export XML?
Director of Photography, Director, Editor
Speed changes are always a b...ch.
I tend to ask my editor to disable them and export a second timeline with all the footage he would like to get graded and then do the retime.
Alternatively you can make some decisions and provide the color grader with retimed clips.
I am in favour of finishing the video part in Resolve entirely and just do graphical overlays in a later stage with Smoke (or FCP if thats whats needed)
When I was finishing FCP > Color > FCP i always baked down the speed changes, so it became habit and do the same in Resolve. There are arguments for and against, but there are no sunrises in Resolve or when you get back...
I would venture to guess that even with the more robust XML in FCPx that the same is true...
And on the plus side, you can bake in the the optical flow you are using