Artefacts after rendering final cut

After speaking with Apple tech pros, the only thing I've found that solved my issue is to optimize any clip you use. This ideally can be done upon import, or afterward in the browser (but not the timeline, meaning if you have existing projects like I do, you have to replace those pieces with the optimized versions) by control-clicking each clip and going to Transcode Media, then Optimize. That turns the clips into more "Apple-friendly" versions that didn't have those crazy issues in the projects or once exported (finally!!!). My problem seemed to be connected to the Catalina update and my type of videocamera, which has an AVC1 codec that is still "acceptable"(ish) to FCPX but not "preferred," hence the optimizing (which I think turns it into a ProRes 422 clip that Apple really likes...or something like that -- I'm no tech expert!!). Not sure if it would work for you, but might be worth a try. Also, the only reason I updated to Catalina was because FCPX would no longer open until I did that; I'm not sure if Apple will eventually force you do to the same. Anyway, good luck to you!

Try deleting preferences. Hold down command and option while starting FCP and click Delete Preferences.

Reopen your library and test.

If it persists, tell us more: what versions of macOS and FCP, what mac, GPU?

Interesting, I was using iPhone native video recording. Who would thought, that Apple vs Apple will not work :)

Anyway, I did two things - removed source video from iCloud synced folder (apparently, MacOS do all kind of f4ery on top of that files even if they are on drive). This helped a bit. But your advice to transcode videos to Optimized format helped a lot. I didn't transcode every file (since it's 30 gig of unoptimized media files), but only problematic ones which were glitching after render and voila! Clean render.

Thanks mate!

Did you recently upgrade to Catalina 10.15? I just did yesterday and immediately noticed the same issues with FCPX 10.4.7.

https://discussions.apple.com/thread/250779422?page=1

What are the specs of the media? Open a clip in the QuickTime player and post a screenshot of the info window. What output setting are you using exactly?

Just a small comment about not being able to create optimized media “from the timeline”: when you select a clip in the timeline you can always use Shift-F to reveal in Browser, and transcode from there. It is NOT required that you replace the timeline clip with a new from the browser (though of course you can). You may have to just delete render files because the glitches.

Do you have any third party apps installed?

Al

The QuickTime player has the correct information. Frame rate data rate is important.

Doors the problem occur in specific shots even if in different places. This looks like a difficult shot to compress, maybe with a lot of motion?

Hi,

Just to let you know I have this problem too on both my iMac and MacBook Pro using 10.4.7 and iPhone 11 Pro footage.

Never had a problem prior's to 10.4.7.

Lets hope apple fix it!

Cheers

Ben

I have just ran off a ProRes 422 export and can see no artifacting like you are experiencing.

Using Catalina with latest supplemental update and FCP X 10.4.7.

I think it may be something specific to your system.

I have no iPhone 11 footage to test on my gear.

Al

Thanks for this knowledge; extremely helpful!! So just by revealing it in the browser and optimizing, the step to replace the clip in the timeline doesn’t need to happen? If so, this saves me a bunch of time!

That is correct, you do not need to Replace.

FCP X will use the optimized version of a clip when it is available.

You may check it yourself by selecting the clip in timeline and look into info part of the Inspector. At the bottom it will show the existing versions; if there is a green dot next to “Optimized” there you have it.

Where is the destination of the export?

Al