I'm happy to report that the issue seems to have been fixed in iOS 14.5 beta 7!
miamitwinz
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Oh great! Fingers crossed!
We filed a bug report, but haven't heard back.
Were you able to resolve this issue?
Hi there, Thanks for your response. We've already filed a bug report on 11/13/2020 titled "iOS 14: copying videos using AVExportSession resulting in audio getting out of sync". We'll add a sample app and media file.
Sure, I'll file a bug report.
P.S. iMovie and Clips appear to work around this issue. We suspect they're using AVAssetWriter instead of AVExportSession.