Syncing audio with video

O.K.

Select the video clip in the timeline and do an Edit/Detach Audio. That will un-embed the audio and leave you with an independent audio clip in the audio well below the video timeline. Then click on the Settings button located above and to the right of the timeline to reveal the Settings dialog box. Use the slider to expand the timeline full out.

Then use one of the following methods to sync the audio with the video.

1. Put your cursor on the audio clip and, while pressing down, slide the audio clip back and forth as necessary to sync it with the video. Another way is to select the audio clip and, while holding down the Option key, tap on the left arrow key (<) to movie the audio clip one frame to the left with each tap, until the audio is synced. Unfortunately, this only works for shifting the audio clip to the left, not to the right with the right arrow key, so you might first need to position the audio clip slightly to the right so you can shift it left until synced.
2. Another way, maybe the easiest, is to Control-click on the detached audio clip and, from the pop up menu, click on Show Speed Editor. That will cause a speed adjustment handle to appear in the upper right hand corner of the audio clip. Slide the handle slightly to the left to speed up the audio clip or slightly to the right to slow it down. Toggle it until the sound is synced with the video. We are only talking about a frame or two of speed shift, so it shouldn't have any discernible affect on the sound. If maintaining the sound exactly as recorded is important, then do the above procedure on the Video clip instead. varying its speed slightly to sync with the audio.

Unfortunately, once the audio clip is detached from the video clip, and then edits are done to sync it, there is no way within iMovie to re-attach it to the video clip and still have it be synced. If you want to re-attach the audio clip and still have it be synced, then you would need to do the syncing process in an newly created project. Then you share out the new project to get an embedded, synced, clip that you can then import into your master project.

-- Rich

Are you referring to audio that is embedded in the video clip, or to audio that is added as a separate clip?

-- Rich