Well. Turns out that if you read this guide for HLS streams, it gives a bunch of details on how the actual video formats should be set up. In particular, for HEVC, it says:
1.10. You SHOULD use video formats in which the parameter sets are stored in the > sample descriptions, rather than the samples. (i.e., Use ‘avc1’, ‘hvc1’, or
‘dvh1’ rather than ‘...
After much help above it looks like its because the camera I was recording on was recording in 50i but the project I had created in fcpx was set to 60p, this was causing issues with the final result as it tried to convert 50i to 60p...
I restarted one of the projects as 25p instead and copied in some of the source video again and a quick repeat of my normal ...
I'm a novice in Resolve, Premiere, and FCPX, but in case none emerges to write up an in-built or automatic procedure, in your place I would think of it as two ops:
First calculate and apply the correct playback speed adjustment. For your example:
clip1: 56-38 = 18 frames difference, 19 frames inclusive
clip2: 40-27= 13 frames difference, 14 frames inclusive
Sorry for panic. Answer has been found.
Problem: Final Cut Pro X was unable to see 4k 60fps videos captured by iOS devices.
Solution: Need to update Final Cut Pro X to 10.4.1 version.
The built-in Credit Tile from FCPX does not work like that. As far as I know, the scrolling speed is determined by the duration and the amount of text.
So if you have a long duration and few text the scrolling speed will be slow and vice versa short duration and lots of text fast scrolling. The Tile makes sure that all text is shown in the duration given.