FCP 10.6 .mp4 audio bug?

Edit: This is only an issue with AC3 audio. .mp4 is not the culprit. Still weird, given that FCPX has supported AC3 since the beginning, but hey. What's an update without a few bugs?

Wondering if anybody else is seeing this issue: 10.6 won't draw audio waveforms for .mp4 clips. Worse, it will barely playback .mp4 clips, and if I have them anywhere in a project, the entire project gets REALLY finicky, and will often give me 15-20 sec of beachball anytime I do a complex operation like: Press play.

Exports with .mp4 media work fine (produce a watchable video), but take 20x as long.
This happens with .mp4 clips with surround audio, stereo audio, mono audio, with the sound encoded in all kinds of different formats/sample rates.

If anybody else is experiencing this, sound off (heh.) If anybody has any ideas about how to solve it, I'm all ears (double heh.)

I have a lot of .mp4 media (movie rips) for the show I produce talking about movies and mental health. This is an integral part of my workflow.

Are you seeing the same issue if you optimize the .mp4 files in FCP?

Investigating further, it may just be .ac3 encoded audio in .mp4 files. Updates soon.

Having the same issue. FCP 10.6 crashing like a mother #%#.   Files are mp4, AAC audio.  Waveforms taking forever to load.  The entire system is completely unstable (2020 iMac 27").  Thankfully I only upgraded 2 or the 4 systems my editors are working on.  At least we're not at a total stand still.   

Thanks for telling me this after the fact, Trevor!  🤪

Has anyone resolved this issue? I'm experiencing the same thing and am going crazy over here lol

My FCP 10.6 crashes when I make a range-volume adjustment, then zoom out of the timeline..

Is this related to the waveform problem, or are your waveforms working? How are you zooming out?

I think it is related to a larger audio issue..
My waveforms also disappear for several seconds after cutting clips.. Never did that before the 10.6 update..
This is what happens: using an audio-synchronized clip, zoom into the timeline.. select a second or so of audio, reduce the volume for that range, then zoom back out..
Crashes 100% of the time when I do this.

I’ll have to try that. Does this only happen on synced clips?

Please use feedback to report this. There are quite a number of problems with this release.

My machine won't play anything back as its stuck 'generating audio waveforms' forever and ever... space bar doesn't play footage back as its clearly trying to draw these waveforms and getting nowhere. Its GH5S footage 4K 10 BIT 422 so not AAC audio, but there is some SFX in the timeline which are aac.

I've managed to get my timeline working again, by deleting generated render files, trashing preferences and moving the cache to a different location, then restarting...

So it definitely seems that m4a files are a big part of the problem. Its not relinking them properly on my projects with 'missing plugin' for m4a files on my machine....

I work with Alan and I can confirm with "our specific projects" it's an issue with AC3 audio. I'm currently working on the new M1 Max MacBook Pro and tried opening one of our projects and the video files with AC3 audio just won't load it's waveforms. I can't play anything in the timeline without beach balling/ freezing. Really hoping the FCP team is reading this thread and gets it fixed.

I'm on an iMac Pro, Big Sur, latest FCP, and my work has slowed to a snail's crawl! It was such a light-weight update! WTF, Apple? ugh...

I seem to be experiencing this same issue on 10.6.1 on a 2020 M1 Macbook Air. Using footage recorded with OBS in an mkv container with AAC audio, remuxed (also in OBS) to an mp4 container for use in FCP.

EDIT: While it's hard to know if my issue was exactly the same as OP, my testing does indicate that my crashing was being caused by clips in an .mp4 container with AAC audio. In my case all that was required was a straight copy of the container contents to a new .mov container. I used ffmpeg (installed with brew, so ymmv) at the command line:
Which recurses through the folder in which its run, as well as any subfolders therein, looking for .mp4 files, and straight copies them into a new container - a process which is not computationally intensive and should finish in just a few minutes even with many large files.

Hope that helps someone.