Synchronize audio from multiple recorders?

I'm working with event videos where the audio is recorded separately on multiple recorders. Lengths are an hour or longer, so small differences in the clocks in each recorder leads to noticeable drift out of sync over time.

My current workflow to deal with this is manual and I'd like to know if there is a more automated way to get the tracks synced over their full length.

Here's what I do in FCPX 10.1.1: I put the main video in the timeline and use it's audio track as the standard. I manually sync each recorder-based audio file to the start of the video's audio. I then go to the end of the video file and use retiming to manually adjust the length of each recorder based audio file.

It works but if there is a way to automate this and get more precise sync all along the track I'd love to know about it.

Thanks!

I'm afraid you are already doing this the best way you can.

Of course you could use the "create synchronized clip" feature in FCPX to automatically synchronize the video with its associated external audio instead of synching them manually. But that will not prevent the audio from drifting over time and you stil will need to open the synchronized clip in its own timeline to adjust the drifting audio.

There used to be a utility called DualEyes than would synch up audio tracks with their associated video while at the same time correcting possible audio drift. But AFAIK DualEyes has become part of Red Giant's PluralEyes and is not available as a standalone app anymore. I don't know if it's worth for you spending 199 dollars on PluralEyes to automatically fix a problem than you can manually adjust in relatively little time. Not to add that the PluralEyes XML workflow is quite elaborate and, just like any automated synchronizing utility, it offers no guarantee for an always perfect result.

- Ronny

Thanks Ronny for your helpful and generous response. This gives me a chance to say how much I appreciate your considerable contribution to the FCPX community with your consistently knowledgeable, constructive and good-spirited responses to so many questions.

I should have mentioned that I tried "create synchronized clip" but the drift between the files was sufficient that it couldn't do an audio-based sync -- or at least I didn't know how to get it to work.

Thanks again -- and know that your generosity is well appreciated.

Hi Robert,

Thank you for the kudos. You are correct, FCPX will not be able to synchronize by audio if the drift between the different audio sources is too big for it to analyze. So I think your current workflow is probably your best choice.

From what I have heard from someone at the company, PluralEyes will not deal much better with this issue (quote): PluralEyes doesn't stretch the audio to correct for drift. It does mask the drift a bit by spreading it out over the length of the clip. So the sync is perfect in the middle of the clip, but each end gets half of the total sync error.

- Ronny