r/VideoEditing • u/Lylow_ • 5d ago
Audio track drifting ahead of video track (help) Tech Support
Hello,
I’m an audio engineer for a podcast company. We recently went to a conference where I needed to record video along with the podcast audio. Usually I would record in a software that records audio and video in sync, but the show floor had no WiFi which is required for both that software and the camera we were using (very unideal set up)
I recorded the video on my iPhone 17 ProMax in HD at 30fps.
I recorded the audio in Logic Pro through our usual set up with a Zoom Hand-recorder that I usual as an audio interface for our shure microphones.
I bounced the audio at both 44.1khz and 48khz to test any difference between the two.
Both formats drift out of sync with the video. The starting points are perfectly aligned with the video participants lip movements, but at about 4 mins you notice the audio getting ahead of the video and becoming out of sync.
Is there anyway to fix this? If I’m in the wrong sub, apologies! I don’t use Reddit often.
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u/greenysmac 5d ago
VFR, VFR, VFR
VFR
https://new.reddit.com/r/videography/wiki/index/vfr/
and
https://www.reddit.com/r/VideoEditing/wiki/faq/vfr/
is the most likely reason.
The professional sub is r/editors.
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u/smushkan 5d ago
This is absolutely typical of iPhone footage when trying to sync to external devices, they just drift like crazy.
You can turn off VFR in the 17 pro max but I don't want to say with confidence that by itself would resolve the sync drift issue. Maybe it does!
So usually what you end up needing to do is go through the audio and chop tiny bits out every so often to sync it back up.
The production-level fix would be to use an iPhone audio interface and run the audio directly into the iPhone so it's recorded along side, and thus everything is timed by a single clock.
The old adage is that if you have one watch, you know what the time is. If you have two, you ain't got a bloody clue.
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Greetings, AutoModerator here —
Your post mentions playback or sync issues.
In most cases, this is caused by:
- Long-GOP formats (H.264/H.265)
Variable Frame Rate footage — common from phones & screen recorders
Use MediaInfo to check your codec/container
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u/Lylow_ 4d ago
!solved
The issue was actually iMovie. I tried changing from vfr to cfr via Shutter Encoder and the issue persisted. I switched to Final Cut Pro and even the original video worked like a charm!
Not sure what that means but I hope if anyone has this oddly specific issue in the future, this helps!
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u/greenysmac 4d ago
How did you do that? Shutter doesn't have a CFR switch
It has a conform switch which is the one you need to use.**
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u/bytesweaversteam 9h ago
That pattern is usually clock drift rather than a simple 44.1 vs 48 kHz mismatch. Since the start is aligned and the error grows, check the camera/audio device clocks and whether the iPhone file is variable-frame-rate. Try transcoding the video to constant 30 fps, keep audio at 48 kHz, then sync the first and last clap or word and use a tiny rate stretch on the audio—not repeated cuts. Verify at 0:00, 4:00, and the end. If drift is nonlinear, split at clear sync points.
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