I've tried resetting the preference files in FCPX and I've restarted the computer as well. But every time I open up Comparison view on my project and I'm adjusting colors, it locks up every few seconds or so for a few seconds. I've even got Youtube in the background playing videos and they'll freeze up too, so it's the whole computer locking up. sometimes my mouse freezes, sometimes it doesn't but the programs freeze up (not able to make adjustments in FCPX)

FCPX 10.4.6
iMac 21.5 inch Late 2013
macOS Mojave 10.14.5
2.9GHz Intel Core i5
16GB 1600 MHz DDR3
NVIDIA GeForce GT 750M 1 GB
SSD Startup Disk

I'm editing a FCPX project that's located on a external hard drive (7200RPM) Thunderbolt 2 external drive. The footage is all H.264 files.

Would converting them to ProRes (Optimized Media) help? Or is this something else?

Not sure, but that shouldn't be a problem for that Mac, really. Verify at least 20% free space on the system drive. Delete all render files via File menu or FCP Library Manager (awesome app). May also be something running in the background that shouldn't be. That is not what I'd consider normal for that Mac. Run Disk Utility and First Aid on all drives, see if that helps.

I've got 200GB's available on my SSD start up disk, and I ran First Aid on both my start up disk and my external drive and both came back good. I also deleted all my render files and that didn't work either. I went back into my project and duplicated the project and started working with it with comparison viewer on. Within 1 minute of using it it froze for about 10 seconds. Used it some more and it did it again. Then I took comparison viewer off, color corrected for about 5 minutes with no hiccups. Turn comparison viewer back on and it freezes within 10 seconds.

I guess my only option is to just uninstall and re-install now. Hope that fixes it or that it's a bug of some sort. Or maybe I need to try converting the clips to Optimized media first? Maybe it's having a hard time with all these color corrections on H.264 files and displaying two at once?

I'm betting on the H.264 files causing the issue. Try it with another project using non H.264 files and also try optimizing as you suggest. Don't waste time re-installing FCPX - that almost NEVER solves anything (only on rare occasions is that a fix and I doubt it will help here). If other files and optimizing doesn't solve the problem - first trash your FCPX preferences and try again - ALSO - make sure background rendering is turned off. If you are color correcting many H.264 clips - the constant random rendering could be bogging down your system some. If the problem still exists, log in as a new admin user (create new account) and see if the problem disappears.

bradywurtz wrote:
If the entire machine and OS is locking up, it's usually not the fault of FCPX or any other user-mode app. If a non-privileged app could lock up the entire machine, a malicious version of that could take over the system.

Run Apple Diagnostics on the machine. No errors does not mean a "clean bill of health" as it's a simple test. However if it finds something it can be significant: support.apple.com/en-us/HT202731

Rebuild Spotlight indexes on each volume, as documented here: support.apple.com/en-us/HT201716

You can also check what kernel extensions are loaded. They run in privileged mode and can lock up the system if they mis-behave: osxdaily.com/2010/08/03/list-all-third-party-kernel-extensions/

Verify each hard drive is delivering expected performance by running Black Magic Speed Test on each one. If a hard drive is intermittently failing or doing re-tries, that can disrupt the system.

If your H264 media is 4k, that can be slow on a 10-core iMac Pro much less a 2013 iMac 21.5. If they are 4k you will need to create proxies for good editing performance. If they are 1080p, performance should be OK without proxies or optimized media, but you could try optimized media. Note optimized media is about 6x the size of H264 originals so disk I/O rates will increase by about 6x. This decreases CPU load at the cost of increased I/O load.

I edit multicam H.264 4K on an iMac Pro with no issues.

hey Brady
Are you running Chrome as a browser? There have been lots of reports of Chrome hogging resources and not releasing RAM while in use. You mentioned YouTube running in background. I would definitely quit any unnecessary apps.
Having said all this, I have had issues with Comparison Viewer but not same issue, so could be a bug.
Could also be a corrupted clip. Outdated plug-in?

Best of Luck, Greg

I think it was the H.264 files. I made a duplicate project first to test it and it was still locking up. then i made a few of the files into Optimized Media, tested it back on them again once they generated, and it never froze up on them. I guess my computer was just being pushed to the limit doing to much color correction and grading on H.264 files AND having to deal with the comparison view.

I normally do multicam edits without generating optimized media though, and i'll have 3-4 cameras at once and i don't get it locking up on me. It's all 1080p H.264 files too. But then again, when i'm multicam editing, the clips are not having any color correcting and color grading done to them at the time of editing all 3-4 tracks at once.

at least the problem seems to be resolved and i have a better understanding of it now, thanks!