Syncing separate audio & 5D video
 

Does anyone have any clever tricks for syncing audio & video when going dual system to replace the 5D audio track when you don’t have the luxury of clapper boards etc? In other words, pure run and gun, no chance to prep, you just have to fix it in post.

I tried it today, my theory being that I could just sync the wave-forms, then replace the 5D audio. Of course I’d never bothered to look at a 5D wave-form before: the AGC turned everything into an almost indistinguishable mess. Nonetheless I did find it pretty quick and easy to sync the video and audio after a bit of to and fro in the timeline.

But that was a first try and I’m assuming it was beginner’s luck and that when I really need to do this on a deadline it will be a different story.

So what’s the secret[s]?

This FCP plugin PluralEyes™ magically does it for you apparently.

I think the hard part is getting a rough match, if you have a lot of video and audio. I do this by watching and listening. Once you find the rough match, just find a word with a hard consonant or peak and line up those waveforms. Anything within 40ms is acceptable, and within 10ms is excellent.

A simple hand clap in front of the camera, preferably at head and tail of scene helps a lot. If you have an iPhone, there's a slate app (with an animated clapboard that makes an audible clap). Also you need to make sure that your separate audio track is running at the same speed...

By using the audio in the camera, it doesn't even have to be in front of the camera. I've verified that the 5D2 mic is well synchronized to the video. If you match the peaks from the two waveforms, it will be sync'd to the video. Also, the most accurate that you can get the sync visually is 33ms (1/30.) By sync'ing to the 5D2 audio, you can get it spot on.

Keep in mind that sound travels at about 1ms per foot, in case your camera (and the built-in mic) is far from the talent.

Oh. Well that's obvious and simple enough then. Built in audio as guide track.

When shooting run-n-gun, I have been mounting my H4n to the hot shoe of the cam. I roll the cam, then the speed (audio) and snap my fingers close to the mics. Gives me a nice peak that I can look for in the waveforms. Easy as pie!

Yes, I tried exactly the same thing this morning and it works brilliantly. So the 5D audio track serves a purpose after all.

Pluraleyes does a great job, used it for the first time over the weekend and it synced up 30+ audio clips from an H4 with the corresponding video clips without a problem (had to change the audio speed on all the clips to maintain sync, but that's the case with any solution).