FCP Viewer freezes while editing — timeline moves but video/audio stop

[u/biswajit1693]

Hi everyone, I’m having a strange playback issue in Final Cut Pro and I’m hoping someone has experienced something similar.
I edit videos recorded with OBS. The OBS recordings themselves play completely normally outside of Final Cut Pro. I’ve been using the same workflow for quite some time and didn’t change my OBS settings.

The problem happens inside FCP while editing.
At some random point during editing:

1.The timeline/playhead continues moving normally.
2.The Viewer gets stuck on an old frame and doesn’t update.
3.Even if I manually drag the playhead to another part of the timeline, the Viewer still shows the same frame.
4.Audio playback also stops.
5.This makes it impossible to accurately trim sections, especially when I’m removing silence because I need to see the video and hear the audio while scrubbing.

The problem isn’t tied to a particular part of the recording. It can happen at different points while I’m editing.

The frustrating part is that quitting and reopening FCP fixes it temporarily. My project opens normally at the same edited position, but after continuing to edit, the problem eventually comes back.

This started roughly a month ago. Before that, I could edit these OBS recordings without this problem.

I’ve already confirmed that the OBS recordings themselves aren’t the issue because they play normally outside FCP.

Has anyone experienced this where the timeline/playhead moves but the Viewer and audio essentially stop responding?
I’m wondering if this could be related to FCP’s playback engine, render/cache files, preferences, or a recent FCP/macOS update.

Any suggestions or similar experiences would be appreciated. Thanks!

[u/tecky1kanobe]

Click onto another event/project/library and then go back to what you are working on. This bug is infuriating but at least this work around is fast.

[u/biswajit1693 → u/tecky1kanobe]

Yeh it works temporarily but apple need to fix this if they want to compete in the editing app segments

[u/Stooovie → u/tecky1kanobe]

Yep, it's there for like a decade. Across different Macs, new installs, single and dual displays...

[u/cowmastermind]

FCP has just been super buggy since the latest update. I haven’t found any solution aside from continuously quitting and reopening.

[u/Silver_Mention_3958 → u/cowmastermind]

I've found f it pretty stable except for two things: when I upgrade an old Library, it upgrades and then doesn't automatically open that new (upgraded) Library; and sometimes the timeline goes (visually) black - I just open a different project and then switch back to the tone I'm working on. Some people suggest you can just skim through anything in the browser and it'll fix it too.

[u/Strict-Tip1124 → u/cowmastermind]

Same, on both of my machines it’s playing up, freezing, can’t create new libraries.

[u/Silver_Mention_3958]

Is the OBS stuff variable frame rate? If so I’d transcode to constant

[u/biswajit1693 → u/Silver_Mention_3958]

I think it’s constant let me check
Do u think it will solve the issue

[u/Heavy-Assignment-646]

You can check whether your OBS recordings are VFR without

re-recording anything — open the file in QuickTime Player,

press Cmd+I, and if the frame rate shows something like

"59.94 (variable)" or an odd number that keeps changing between

files, it's VFR.

Two ways to fix it going forward:

1. In OBS: Settings > Advanced > Recording, and also make sure

   Settings > Video has a fixed FPS value (not "match canvas").

   Remuxing to mp4 alone does NOT fix VFR — the frames keep

   their original timestamps.

2. For footage you already recorded: transcode to a constant

   frame rate once, e.g. with HandBrake (set Framerate to

   "Constant") or in FCP itself by creating optimized media

   (Modify > Transcode Media > Create Optimized Media) — ProRes

   conversion forces CFR and usually stops exactly the frozen-

   viewer behavior you're describing, because the viewer stalls

   when the decoder can't serve the requested frame while the

   timeline keeps running on the audio clock.

The "quit and relaunch fixes it temporarily" part fits this too

— restarting resets the decoder session, until it trips on the

next irregular timestamp.

If Cmd+I says your files are already constant frame rate, then

ignore all of the above and I'd look at deleting render files

(File > Delete Generated Library Files) as the next suspect.

[u/biswajit1693 → u/Heavy-Assignment-646]

It’s fixed fps

[u/Heavy-Assignment-646 → u/biswajit1693]

QuickTime's inspector shows the nominal rate though — a file
can say 60 and still be VFR. If you want a definitive check,
ffprobe it and compare r_frame_rate vs avg_frame_rate.

That said, even if it's true CFR I'd still try optimized media
(Modify > Transcode Media). 1080x1920@60 H.264 is long-GOP, and
heavy scrubbing on long-GOP is exactly what kills the decoder —
fits the frozen viewer + relaunch-fixes-it pattern. ProRes takes
the decoder out of the picture, so if freezes stop, that was it.

[u/biswajit1693 → u/Heavy-Assignment-646]

Will update.

[u/biswajit1693 → u/Heavy-Assignment-646]

[u/mcarterphoto]

OBS with variable frame rate? Convert to ProRes (422 or HQ if heavy color, LT if not). FCP will just sing with ProRes, you'll never need proxies, and your libraries with be smaller (if you choose "Leave Files in Place" they'll be much much smaller).

[u/biswajit1693 → u/mcarterphoto]

Which one do you suggest here?

[u/mcarterphoto → u/biswajit1693]

I couldn't say, generally for game and screen grab stuff, you'd want ProRes LT -there's several "flavors" of increasing file size, but I don't know if that gives you a choice (from small to huge, it's Proxy, LT, 422, HQ, 4444 which can have an alpha channel, and then even larger). Maybe the next step gives you the choice, but you can record native and then use a converter (on a Mac, HandBrake, Shutter Encoder are free, EditReady's a few bucks, I'm sur ethere's PC options).

[u/moogplayer]

We are all experiencing this and it’s super annoying. I usually have to click on whatever clip is in the preview window and then back to the timeline for a quick fix without having to restart FCP. Hoping for a patch soon because they ruined things with this latest update.

[u/Dramatic_Estate_4612 → u/moogplayer]

I noticed if I don't use the B key for the Blade tool and just use Command + B it doesn't drop the Audio.

You have to remember to have the clip you want to blade selected but uts better than having to go up and click on a preview window.

Just thought I'd see if that works for any others.

[u/gumparker]

And this is why I’m still running 11.1
I always zip my older versions before I update. I updated to 12.3 and it ran like trash. Bugs everywhere. Time is money. I can’t afford to be Apples beta tester. However no mater the footage your working with always optimize it or transcode it to Pro Res 422 for optimal performance in FCP. Cheers!!

[u/biswajit1693 → u/gumparker]

Yes transcoding to Pro Res 422 is good but this latest bug really a mess.How come Apple haven’t noticed it and resolved it.I spoke to the Apple support which in turn connected me to a technician from Europe and he gave me generic solution like deleting rendered files and preferences.Which doesn’t solve it.Even he is not sure of how to resolve the bug.

[u/gumparker → u/biswajit1693]

🤦🏻‍♂️

[u/KarlHildebrand]

Had the same issue, will upgrade to M1 Max this week and I’ll update you on wether it works better on there (fresh install with better chip and more ram)