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25 Jan 2021
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Asynchronus AAC-Audio in exported Video 09 Jun 2021 09:17 #114933

Hello FCP.co-Community!

I hope you can help me with this issue. I create social media videos for a public broadcast company in Germany but I’ve noticed that the sound of all my exported videos are out of sync by one frame since weeks ( I believe since updating from Mavericks to Big Sur)

My setup:
MBP 2015, latest versions of macOS Big Sur, Final Cut and Compressor.

My workflow:
I import my source video (Linear PCM, XDCAM HD422 1080i50 (50 Mb/s), 48 kHz, 8 Mono Channels) cut a 1-2 minute long video, add effects and some music (also 48 kHz) – everything works fine.

But then I export my video as 1080p25 H.264 and AAC Audio (48 kHz) and the result is a video with asychronus audio by one frame.
When I put the exported video on the timeline of the edit in Final Cut, I can see that the last frame of the exported video is silent. It seems that Final Cut cuts off the audio of the first frame of the video and moves the whole audio one frame forward and fills the gap with silence.

I’ve tried several settings and presets in Final Cut and Compressor, but every time I use the AAC Codec, the final video has asychronus audio. If I export the video with Linear PCM everything works fine.

One strange thing is: exporting only audio as AAC with no video directly from Final Cut doesn’t produce this failure.

I hope you can help me out with a solution for this problem, because it’s very annoying exporting video and audio separatly and do the final export in Premiere Pro.

Best regards from Germany.


//EDIT: I've uploaded a sample source video (Linear PCM, XDCAM HD422 1080i50 (50 Mb/s), 48 kHz, 8 Mono Channels), perhaps anyone can test an export with AAC-Audio: www.dropbox.com/s/tv4y6c9x53ll9jr/Einspieler-dersee.mxf?dl=0

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Last edit: by daenjiel. Reason: added link to a sample video

Asynchronus AAC-Audio in exported Video 09 Jun 2021 14:58 #114937

I testet some more:


On the first picture is an iPhone video (30 FPS and 44,1 kHz AAC) on top. I exported the video with FCP and Premiere Pro and both results are out of sync compared to the original, but the audio of the FCP version drifts more than one frame!


On the second picture is the HQ video (Linear PCM, XDCAM HD422 1080i50 (50 Mb/s), 48 kHz, 8 Mono Channels).
Here also the audio drifts, but not so much on the Premiere version.

Why does this happen? The video frames
Attachments:

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Last edit: by daenjiel.

Asynchronus AAC-Audio in exported Video 13 Jun 2021 20:07 #114981

Ok, it seems to be a deeper problem in macOS. just installed Big Sur 11.4 on an external drive and exported a H264/AAC video as H264/AAC video , same audio jump by 1 frame …
What can I do? Any suggestions? Please, I need some help!

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Asynchronus AAC-Audio in exported Video 21 Jun 2021 03:02 #115079

I had the issue too and made a thread on it. No solutions. It appears to just be a bug with Final Cut Pro with AAC audio involving Big Sur sadly. I hoped it would be fixed with the latest update but it doesn't mention it.
www.fcp.co/forum/4-final-cut-pro-x-fcpx/...h-m1-mac-and-big-sur
www.reddit.com/r/finalcutpro/comments/mh...htly_out_of_sync_on/

A pretty bad bug. After I make files with Final Cut Pro, I put them in AviDemux and shift the audio 50 ms. That at least aligns it with the audio waveform. I just hope the video isn't moving any either.

Post if you figure anything out

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Last edit: by David814.

Asynchronus AAC-Audio in exported Video 03 Sep 2021 08:30 #116104

Hi,
I found the thread because I encountered the same issue but I'm actually on Catalina 10.15.6 with FCP 10.4.8 so I don't think the OS is the problem.
The weird thing is that I have the exact same FCP version on a Mac running Mojave and the issue doesn't happen there...
I'm starting to believe Pro Video Formats update could be the cause (it's literally the only difference between my 2 MacBooks) but not sure how it cold be related...

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