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14 Nov 2020
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TOPIC: iPhone footage out of sync with itself

iPhone footage out of sync with itself 15 Nov 2020 18:54 #110878

  • flaminghick
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I've been editing iPhone footage in FCPX for years and I have recently encountered an issue since some version of FCPX 10.4. I don't remember exactly which version. The iPhone footage is out of sync with ITSELF. The audio plays around 4 frames in advance of the visual in both the browser and the timeline


I checked the footage in the Finder and it plays in sync. I have no idea what's going on here but it necessitates unsynching all the footage and pushing the audio down in order to synch it back up. This isn't specific to one computer as with FCPX 10.4 it was happening on both an iMac and a MacBook Pro.
I am now working in FCPX 10.5 and have the same issue.

If anyone has any insight into this I'd appreciate it. I can't imagine what would fix it aside from an update as it seems to be a bug.

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iPhone footage out of sync with itself 15 Nov 2020 18:58 #110879

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Can you give the media specifications and the project properties? iPhone is very problematic because of its unstable frame rate. You might try optimizing the clips, that helps with a lot of iPhone media problems.

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iPhone footage out of sync with itself 15 Nov 2020 21:31 #110883

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Sure I can tell you but for context I've been using the same media specifications for years without this issue. I have never had any issue with iPhone footage and I've found it to be the opposite of problematic with no issues I can recall. Keep in mind I'm not syncing it with externally recorded audio, it's the audio recorded with the footage I'm talking about. It's consistently out of sync with itself so I really don't think it has anything to do with dropped frames or drift. And since it's out of sync in the browser, I realize now the project properties are irrelevant, but I'll tell you everything I've tried just to see.


I've been shooting 4k on the iPhone for as long as I've been able to (High efficiency for as long as it's been available) and my project properties match the footage, 44hz audio,. Used to use 30p, now I'm using 24p, the issue is the same with all of the footage regardless of frame rate, High Efficiency on or off. I recently started using HDR footage and it's the same as SDR footage. Consistent issue no matter what's imported. I tried changing the frame rate and the issue is the same. Tried changing the audio from 44 to 48 even though 44 matches it, same issue. Nothing affects how out of sync it is, browser or timelineSame 4 frames no matter what, unless I watch it in the Finder.


Thanks for your response, and I appreciate any invite you might have. I've submitted feedback to Apple a couple times now as well.

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iPhone footage out of sync with itself 15 Nov 2020 21:46 #110884

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I’d suggest converting a free clips in an external application and say if it stays in sync. Are the clips in sync in the QuickTime player?

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iPhone footage out of sync with itself 15 Nov 2020 22:18 #110885

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Great idea I'll give it a try. Yes the clips are in sync in Quicktime

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iPhone footage out of sync with itself 15 Nov 2020 22:29 #110886

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So I tried it with a couple clips and I'm getting the same issue. Very strange.

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iPhone footage out of sync with itself 16 Nov 2020 16:34 #110893

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flaminghick wrote: So I tried it with a couple clips and I'm getting the same issue. Very strange.


I haven't seen this but I rarely edit iPhone HEVC material. This video discusses the problem (which may not be unique to FCPX) and suggests not using HEVC and for existing material, transcoding to constant-frame-rate using Handbrake:


Some say that using the 3rd-party app Filmic Pro can produce contant (or maybe pseudo-constant) frame rates on an iPhone: www.filmicpro.com/products/filmic-pro/

However there was a bug in Handbrake (apparently now fixed) which implied some issues with Filmic Pro material last year: github.com/HandBrake/HandBrake/issues/1802

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Last edit: by joema.

iPhone footage out of sync with itself 16 Nov 2020 16:50 #110896

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Hey thanks for your response. He seems to be talking about drift here. The issue I'm having isn't drift. The audio that is recorded on the actual iPhone is out of sync with itself, and it's consistently out of sync. Within the first few seconds of the video it's 4 frames off, and later in the clip it's 4 frames off. But it's the original audio recorded with video from the same file on my iPhone. It's in sync when I watch it in Quicktime or on my phone, it's just out of sync as soon as it's imported.

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iPhone footage out of sync with itself 16 Nov 2020 18:06 #110898

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It's a little suspicious that it's almost immediately 4 frames off and this doesn't increase over time. That is similar to typical video processing delays of HDMI interfaces and external monitors.

Do you have any outboard video display hardware - hubs, converters, monitors, etc? Any outboard audio, inc'l wired headphones or wireless AirPods? As a test can you disable Bluetooth on the computer and try that. Do not use any external video hardware or headphones (esp. wireless) for this test. I realize that doesn't explain in-sync Quicktime playback, but it's an easy test to do.

What if you transcode the HEVC material within FCPX to optimized media? Does that make any difference? That could avoid HEVC decoding overhead.

If you had another NLE such as the free version of Resolve it would be interesting to see if it happens there.

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iPhone footage out of sync with itself 16 Nov 2020 19:42 #110899

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These are honestly all great troubleshooting ideas. I disconnected my monitor and headphones and it's still the same. I restarted the app and it's still the same. Since it's also happening on my iMac I didn't think it would be the monitor. But I do find it interesting that it's around the same amount of delay as with bluetooth headphones. Except...with bluetooth headphones wouldn't the audio be delayed, rather than ahead of the footage? Here the audio is 4 frames ahead.


Your idea to test another NLE is a great one. I was also thinking I should pull in some footage from a different source to see if there's something about the iPhone footage itself that could be causing it. It doesn't seem like this is a widespread issue at all.

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iPhone footage out of sync with itself 16 Nov 2020 19:47 #110900

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And I also did a transcode test to optimized media and it there was no change.

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iPhone footage out of sync with itself 17 Nov 2020 12:39 #110907

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flaminghick wrote: And I also did a transcode test to optimized media and it there was no change.


Can you shoot a short test clip, verify that it's delayed, then upload it so we can test on various Macs and FCPX versions? I can also test it on Premiere and Resolve.

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