I seldom shoot high speed footage on my phone, but from past experience, I assumed the process of getting a file that would work in HitFilm would be straightforward. Sadly, that wasn't the case yesterday, and I'm curious if anyone can spot something I did wrong.
As always, my first step after importing the file to my computer is to transcode it into something that's HitFilm-friendly. Handbrake has been my go-to for a while, using the "Norman AVC" custom preset I built a while back based on tips from @NormanPCN . Handbrake correctly read the high frame rate of the file, so I thought the output would work if I left the frame rate setting on "Same as source". However, after bringing the transcoded file into HitFilm Pro 14, the "from file" frame rate was showing as 60fps, not 240.
Curious how the original file would import, I tried that next, only to have the same result, which really blew my mind. How can Handbrake (and even Quicktime) recognize it at 240fps, but HitFilm see it as 60?
My next thought was to manually change Handbrake's output frame rate to 240, but sadly the drop-down options only go as high as 120, and there's no manual input to override it.
My next test was to try transcoding using my former favorite, MPEG Streamclip, where I knew I could enter the desired output frame rate manually. I could also trim the clip down to just the piece I want, which Handbrake doesn't allow. After transcoding and importing into HitFilm, it was read at 240fps, and my initial test of forcing it to 30 in the clip settings appeared to show that all was well.
I went ahead and edited the project, not worrying about frame-accurate playback during editing because I know my machine isn't the best at that, which is why I didn't notice the next oddity until after it was exported. When the slow-mo footage kicked in, the first several seconds of it felt stuttery, not smooth, and then things smoothed out to the end. Opening the file in Quicktime, I found that the opening stuttery part wasn't playing every frame of the original 240 fps footage, but every other frame, and that at some random point it switched to playing every frame.
I went back into HitFilm and confirmed that the anomaly was showing there, so I assumed it might've been some hiccup in how HitFilm interpreted the footage. However, I then opened the transcoded file made by MPEG Streamclip—the one that I thought was working properly—and found that the problem was there as well!
As a test, I went back to MPEG Streamclip just now (as I began typing this) and set it to transcode the same file again, this time without trimming it. It just finished a minute ago, and a quick look shows that the frame-skipping problem is still there, only now in different parts of the video than in the trimmed version.
Any idea why this is happening with MPEG Streamclip? Any idea why HitFilm somehow sees some 240fps footage—the original file, or the one transcoded via Handbrake—as 60fps? And most importantly, any idea how to fix any of this? I might try a test with 120fps footage later on and see if there are similar problems, but I somehow suspect there won't be.