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Audio doesn't Sync right

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Abbey Hoekzema
Audio doesn't Sync right
on Feb 26, 2014 at 7:12:31 pm

I am attempting to sync audio in FCP X and it's not lining up the material correctly. However, when I run it through Premiere and Plural Eyes everything syncs fine. I don't understand why this is happening?


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Bill Davis
Re: Audio doesn't Sync right
on Feb 26, 2014 at 8:14:56 pm

Hi Abby,

There are a few possibilities.

The first group is related to how you're establishing the sync point. In X, the default is a waveform sync (just as in PluralEyes an other solutions. But that's not the only way to sync in X (nor necessarily the best way) X also provides sync by Markers, by timecode and a few other options. In my experience, most sources sync up well in X, including situations such as syncing cameras like GoPros where the only audio reference comes from a marginal quality on-camera mic. In circumstances where it doesn't work as well - placing a marker on the video and audio you're trying to sync can give X a "head start" in order to make the sync easier.

But none of that helps with the second issue, which is that many, MANY sync issues stem from audio sample rate conflicts. If you have a video source record at, say 48khz. And you're syncing to second system that's been synced at 44.1khz, it's going to be difficult to get them to line up for very obvious reasons. Now a program can elect to MAKE them match by auto-resampling - but that begs the question what does the user want the "match sample rate" to be? Lots of times, it doesn't matter. But for the sophisticated producer, it's often not something you want the program to decide for you.

Which brings me to a wider point about how FCP-X has been designed. There's a whole lot about the program designed to make user operation EASIER. But below the surface of that stuff, there's a word of almost RUTHLESS precision built into the program. When you ask it to do a task, it's NOT going to dumb down the TASK itself, rather it's going to try to simplify the way the user experience doing the task.

I first noticed this in the early days of X when I did scene composites. I'd drop two video clips with, perhaps a really high rez still image background - and when X went to composite that into a final scene, it took FOREVER to render out. I came to realize that was because the program was trying to map and calculate the zillion pixels of my huge still image onto the pixel values of my two video images and was doing a boatload of math as a result. When I simplified the huge still image into a picture the same size, but with far fewer pixels "under the surface" the composite was done in seconds.

And thats a very, very long winded explanation of POSSIBLY why you're having difficulties. You have some audio sampled content that you're telling X to sync. And it's unwilling to make presumptions about HOW you want it to sync.

Just like I had to make my still images simper, so that X wouldn't waste time trying to calculate pixel values that didn't matter - you might simply make sure that the audio files you're trying to sync are in a form that makes SYNC simple.

I'm a big fan of the free MediaInfo utility that you can drag and drop a digital content file onto and it will show you what the underlying file attributes are. Try that with the audio and video files you're trying to match up and see if there's a miss-match.

If so, that's your issue.

If not, it's something else and I'm totally off base. (Equally possible!) But at least it will give you some understanding that sometimes elements of how X works that seem like they're problems are actually the result of X taking a "high road" approach to content quality issues. Not always, but some times.

Good luck and let us know how things work out.

Know someone who teaches video editing in elementary school, high school or college? Tell them to check out - video editing curriculum complete with licensed practice content.

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james Lackleter
Re: Audio doesn't Sync right
on Feb 27, 2014 at 4:25:20 pm

What is the frame rate of your video? Do not use multiple frame rates in this program.

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Dave Jenkins
Re: Audio doesn't Sync right
on Mar 1, 2014 at 3:37:59 pm

make sure the audio rates are the same. 44.1 or 48k FCP X won't sync mixed audio rates.

Dajen Productions, Santa Barbara, CA
Mac Pro 3.5MHz 6-Core Late 2013

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Mark Boisvert
Re: Audio doesn't Sync right
on Oct 2, 2014 at 1:55:08 pm

It does this for me all the time.

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