Audio and Video Synching Problem with IMovie and the MAC OS (Catalina)

Hi, Ted,

Sometimes if the video was recorded in Long Play rather than Standard it can cause sync problems. Also, the sample rate of the audio can affect the sync -- 44.1 (slower), 48 (faster).

Try duplicating your project and, working with the duplicate, split the clip in two places to make a segment where the audio is starting to drift out of sync. Then detach the audio and see if you can manually sync it by nudging or dragging the audio clip along the timeline. Also, you can try expanding out your timeline (slider next to Settings Button above the timeline to the right), then select the audio segment and do a Control-click to get a pop up menu where you can select Show Speed Editor. That will reveal a slider handle in the upper right hand corner of the clip that you can slide to the right to make the clip slower, or to the left to make the clip faster. Try syncing the segment that way.

A trick to get more precise syncing is to select the audio clip and, while holding down the Option key, tap on the comma key on your keyboard, the one with the < symbol on it. That will nudge the clip to the left one frame with each tap of the key. It only works with nudging left, not right, so you will first need to position the audio clip to the right before nudging left.

In case it is a formatting issue, you could also try using the free download, Handbrake, to re-encode the clip to H.264, Mp4/AAC, that Handbrake will do by default. See if the re-encoded clip is properly synced. You can get Handbrake here:

https://handbrake.fr/

If none of the above works, you might try an audio editing app, like Audacity, to shrink or stretch the audio clip to sync it, or to change the sample rate.

-- Rich

You are very welcome.

Converting with Handbrake also runs the audio through the re-encoding process, in case there is some issue with the original audio clip. If you try it, work with a duplicate movie so you preserve your original.

You might try putting your video clip into a newly created project and then sharing it out as an audio only file (an option from the share box). You will have format options available. Share it to AAC or aiff. Then import the new audio clip into iMovie. Mute the video that is already there, so it plays no sound. Then play the timeline with the new audio and see if it will sync up.

-- Rich

I think we have reached the limit of what can be done on an electronic forum such as this one.

You might benefit from contacting Apple Support and speaking with one of the savvy techs there. They have the capability of remotely accessing your computer, that we cannot do here. Click on the Contact Support item in the upper right corner of this forum’s screen. Navigate to a place where you can give your phone number and support will call you back.

Good luck with this. I hope that the support folks can find the answer.

— Rich

Also, try sharing out your video using Best Quality (pro res) as that format uses a slight different audio codec. You will get a 4x larger file, but that might not matter if you can get the audio to sync.

-- Rich

Sound issues have commonly been reported when importing from tape based cameras. It seems that the newer software doesn’t do it as well as the older versions, like iMovie 9 and the old iMovie 6. I’m not aware that Catalina has had particularly more events in that regard. The reports have arisen with all recent operating systems. However, you could use the search function of this forum to see if you can find any unusual correlation with Catalina.

— Rich

You are welcome. Audio sync problems can be pesky, indeed. Did you try converting with the Handbrake app, as I mentioned in a previous post?

Once an audio clip has been detached from a video clip the only way to reattach it within iMovie is to do an Edit/Undo as many times as necessary. Any edits that you did after detaching the clip would also be undone. One way to reattach previously detached audio is to share out the video clip and audio clip from a newly created project for the purpose. That will merge them back together again in the shared out movie, that you can then import back into your original project.

Here are a few more tips about working with audio clips:

You can split audio clips (Modify/Split Clip) at different places and move the segments around as you need to. If you hold down the Option and Command keys you can click along the audio track to move the attachment point to the video above. You can also press-drag an audio clip downward to a lower audio well until the attachment handle pulls off of the video above. That will make the audio clip independent of the video clip above it.

-- Rich