background tasks not complete message

When exporting that message

"x_Sequence " has background tasks that are not yet complete. "

If you continue, these effects may be missing or have reduced quality:

Retiming - Optical Flow "

acts like a virus you won't get rid of

no matter if you check any clip concerned in the timeline and confirm analysis done ... it still pops up !

should I ignore it ?

I ran into this exact issue this week when retiming some time lapse work with optical flow. After waiting about 10 minutes with no resolution, I exported anyway, and the resulting file looked fine. The only way I was able to remove that message was to find the cache folder for that library (which was stored on an external drive) and drag it to the trash. Then, when opening that project, I had to reapply optical flow and it completed successfully with no error message on export. I should add that the exported file (after removing the cache) looked no different than the exported file before removing it. I think this is somewhat buggy behavior with optical flow and in my case it occurred after re-timing, applying it, and then re-re-timing (changing the speed again) and trimming the same clip a few different times. Seems like the analysis gets a bit lost or confused when doing that. Maybe it's best to get the clip completely trimmed and retimed how you want it, and only then apply optical flow to it. This does not seem to be a consistent problem, but it does occur every now and then (at least for me).

We've had this bug for awhile now.

yep dgw ! I appears that once some analysis was not right at some time it will pop up anyway. Even if you export as little as a single clip from the timeline without any retiming !

I didn't go for the brutal force of trashing the cache, but good to know that you really start afresh doing this.

The message must be looking at something else in the timeline that has optical flow, even though you are trying to export a clip without it. Optical flow is never available on a clip that is not retimed and only appears selectable when retiming is active, but the message bug can appear I believe if the project ever contained any retiming. Trashing the cache is not that brutal, but if you have many clips (especially long ones) with optical flow in your project, they will all have to have it reapplied after doing so, and maybe that could be brutal.

Yup, seen this myself quite a few times. It does seem like a bug. I just check the timeline, as long as all those little white dots showing clips being rendered are gone, I just go ahead and export anyways. Its always a retiming issue, never anything else. And just like everyone else, the footage looks fine. Glad to hear I'm not the only one with the issue.

Same here.. after so many years.. Did anyone find a solution in the meantime? Or is the only way still trashing the cache? When I do so: Do I have to set all my retiming information like speed ramps again or do I just have to set the retiming method back to "optical flow"? This could be done quite quickly.

Trashing settings doesn’t change anything applied to clips in the browser or projects, only the settings in the FCP menu.

not settings.. the cache.

In this case I think I found the solution: I had applied a speed ramp to a clip with optical flow applied. Then I set the speed to normal - but optical flow was till activated. I guess FCPx thought It has to render the effect, but didnt know how. I am still curious if there isa general fix to those issues now.

Trashing the cache only removes render components. It doesn’t change anything set in the application. 

So is there any other solution? Today I have to render out the documentary in multiple formats and this "background tasks" error shows up again and again.. Some clip with optical flow... but I have applied it to many many many clips.. so impossible to find out which one is the caus