FCPX audio drift

It's possible the iPhone variable frame rate is confusing FCP. Try optimizing an iPhone clip (right-click and choose Transcode...), create a new project with that optimized clip, then export it as default and see if the audio drifts. Make sure you have sufficient free disk space as optimized files are ProRes and can be quite large.

chrismeibusch--glad you found a solution. I can understand this happening on a full and/or slow external drive. Your master file export data rate might be too much for the drive to keep up with so it can't play the file properly, leading to audio out of sync.

You're very welcome. To speed your journey to mastering FCP, I highly recommend these two free tutorials by respected FCP editors. These will save you from many, many hours of frustration.

Steve at Ripple Training, 60 minute FCP tutorial overview https://www.youtube.com/watch?v=HqUP7Zgeuck

Izzy Video tutorials https://youtu.be/_jvyrnQpR1E?list=PLp5SAgbM8S87n1qvv34-PAU2zMHLlXyfb

No. Do the same to the timeline clip.

Did you try Terry’s suggestion to optimize?

You’re saying that if you export to the external drive the sync drifts on the exported file, but if you export the same project to the internal drive, the same way, there is no drift? That makes no sense. There’s something else going on with system.

You could try changing the audio sample rate for the project from the default video production 48K to the iPhone's obsolete 44.1. That might work and be a simple fix for you.

The method I was trying to explain is this:

Select the clip in the browser and then use Open Clip from the Clip menu. That opens the clip into the timeline with it's audio and video separate.

Select the audio and in the Retiming menu select Custom

You want to adjust the speed of the audio so that it matches the video. You can't adjust the speed percentage in increments more precisely than one percent. You can though set the duration of the audio, which can be more precise.

You might also try changing the audio sample rate of the clip using Compressor from the iPhone's 44.1 to the video production standard 48K. In Compressor you can leave the video untouched and change just the audio. The job output would look like this with the video in pass through so it's not recompressed.

I understand.