I have a few clips in the time line that I have speeded up and have chosen the Machine Learning retime quality setting. Every time I export this time line, I get this error message:
However, if I cancel this and open the Background Tasks window, there is nothing going on.
If I choose CONTINUE, the exported file is fine, and the speeded up scenes play properly in high quality.
What's going on here?
This bug was manageable previously: it happened only rarely, and you could delete the Optical Flow folders inside the Final Cut Pro cache bundle (with the app closed) to force Final Cut Pro to reanalyze the affected clips. You may have had to Render All, click on every retimed segment, or force a Render on each of them, but everything would eventually analyze, and that warning would no longer pop up.
Since upgrading to Final Cut Pro 12, I encounter this issue on every single project that uses Optical Flow (“Best” / Machine Learning), and none of the workarounds above have worked. Worse, I now experience severe artifacting in many of my clips, with flashing images at various points of the retimed segments.
There doesn’t seem to be any pattern to it, with 3-minute clips playing back just fine after the export despite the “background tasks” warning. On the other hand, some 20-second videos are severely affected, exhibiting very jittery playback of the exported file.
I’m going to submit a sample project to Apple, but in the meantime, traditional Optical Flow (“Better” / non-Machine Learning) seems unaffected, at least on the projects I’ve tested. If your project doesn’t need the benefits of the Machine Learning algorithm (eg. occlusion detection), you could try that.
It's a bug that has gotten better, but never has gone away 100%. I normally ignore it and everything exports just fine.
This all makes me wonder if it might have been caused by 26.3, as other issues were discovered relating to graphics during the cycle. I couldn’t mention this before, but the update has been now released.
Since it is a long time ongoing bug, I doubt 26.3 caused anything new.
Zecanard, I have not experienced the problems you have. However, your suggestion to use Optical Flow instead of Machine Learning is a good one. I will try that the next time I have to retime a clip. For the work I do, I think that level of quality would be fine.
Well how about that.
I never had this issue until after I updated to FCP 12.
I have not had this issue in 12 at all. But yes, I hate the ML interpolation of slow-mo, it is horrible. I always end up using Optical Flow (which has it's own serious limitations).
A Non-Existent Background Rendering Issue
