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Audio Sync Issues In FCP

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Ray Junior
Audio Sync Issues In FCP
on Mar 20, 2014 at 8:16:01 pm

retina macbook pro
2.5ghz i7
8gb ram
ssd internal drive (app)
external usb 3 7200rpm drive (media)
os X 10.9.2
fcp 10.1.1

Hi all-

i'm brand new to FCP X (still have 7 installed even). Having a weird issue with audio that I can't seem to figure out.

I recently recorded a 15 minute interview using 2 cameras - an iphone 5 and a canon hd cam (sd card recording in full HD). The iphone used room audio and the cannon had a lav mic attached to it from the subject.the goal is to sync the two clips together in post and then eliminate (or mute) the audio from the iphone cam.

After importing both clips into FCP I can get the two clips exactly aligned visually with the clapboard. the iphone clip starts in just about perfect sync (still needs a frame or two adjustment) but by the time i get to the end of the clip it's off by more than an entire second!

If i quit FCP X and launch 7 and do the exact same thing, there's no problem with audio sync.

This is a brand new FCP X install and as far as I remember is pretty much in the stock config.

any ideas?

I don't know if this means anything or not but the audio waveforms for the two different clips do not look identical in X (as they do in 7).

Another oddity - the waveform for the iphone audio appears to be a light grey in the background with what almost seems like a light/translucent grey overlay over the entire thing.

thanks in advance for any ideas.


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 3:05:19 am

What frame rate are the clips?


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Ray Junior
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 10:56:15 am

oh wow I hadn't even thought to look at that-

FCP says the iphone video is 30fps

and the other cam is 29.97i

i'm a bit of a newb here on how to solve this problem, but I'll bet you're on the right track with the different frame rate differences

since i'm new to fcp i have no idea how to correct this. any thoughts or solutions would be greatly appreciated

thanks!


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Bret Williams
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 2:53:30 pm

In another thread, I recently discovered that X is automatically conforming some frame rates to the timeline rate if they're close. For example, 24p in a 25p sequence. X conforms the 24 to 25 without any notification. It doesn't display it in the retime controls either. This is probably happening with your 30p material. It's playing it back at 29.97. A little slower than it should. So over time the syc gets off. If you had an end sync point you could drag out the retime effect until it matched. Or you could try adjusting the custom speed to 100.001001% speed if my math is correct.


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 3:09:08 pm

What Bret says, although I would challenge on "who" exactly discovered it. ;P Just kidding!

If your frame rates are mismatched, then X is doing an auto conform, and it doesn't report it.

What frame rate is your timeline?

It should be 29.97.

When you add the 30.0 iPhone clip, you need to select the clip and choose the "automatic Speed" from the retime drop down. This should then show a slight speed change.

Then open the "Custom speed" panel and set the duration to the exact length of the 29.97 piece.

FCP7 doesn't do this because 7 doesn't work this way. I also think that this is somewhat of a bug in FCPX and would be worth reporting to Apple if you haven't already.

Jeremy


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Ray Junior
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 3:34:51 pm

thanks to all of you replying!

the project says it's 29.97i - is that the same as 29.97 or does the "i" men something significant?


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Bret Williams
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 3:46:08 pm

Sorry if you discovered it. You weren't in that thread the other day. I may not have been first, but I did discover it independently.

When he does the auto speed, it will do a double conform though. It's already done an auto speed in the background. Adding auto speed will just make it slower again because X still thinks it's 30p even though it's already conformed it. Then you'll have to seed it up by a higher percentage like 100.002% or something.


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 3:49:12 pm

[Bret Williams] "Sorry if you discovered it. You weren't in that thread the other day. I may not have been first, but I did discover it independently."

I was just horsing around!

[Bret Williams] "When he does the auto speed, it will do a double conform though. "

The point is to get it out of the weird "non-reported" state. You will also notice that the preserve pitch box does weird things as well. I find letting FCPX do the auto speed and then entering a new duration works the best for me, but perhaps there's a better way.

I'd rather work in duration than percentages as you can get more accurate (to the frame) on the duration.

Jeremy


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Bret Williams
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 4:06:53 pm

Hmmm. Are we sure it's doing the hidden conform? I just tried some 30p iPhone footage in a 29.97 sequence and it retains duration to the frame over a 5 min span. With the 24p in a 25p sequence, the duration would shorten as you took it from the event to the timeline. Then doing an auto speed makes no change to duration or speed. Leaves it at 5min and 100% speed.

In the 25p sequence, the 24p clip is sped up without notification. Still reads 100% but the duration of the clip gets shorter. Then doing an auto speed shortens it further and then adds the % change.

But my 30p footage in a 29.97 is holding true. I don't know if it's dropping a frame every minute or so but it's holding true in duration at least.


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Robert Gilman
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 4:19:19 pm

When I do an event with external audio recorders I find that the clock rates in the camera and the audio recorder aren't exactly the same so even if the reported "duration" says it's the same the waveforms don't match. There may well be a better way but I just sync the audio at the start and then go to the end, turn on retiming and drag the retiming handle until the I have waveform sync at the end.


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 4:20:28 pm

[Bret Williams] " I just tried some 30p iPhone footage in a 29.97 sequence "

How long is the clip?

If there's not enough length, there won't be much of a difference as there isn't much of a difference.


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 4:23:59 pm

Also, here's another thread for reference:

http://forums.creativecow.net/thread/344/28167#28167

Jeremy


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Bret Williams
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 4:42:15 pm

Just over 5 minutes.


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Ray Junior
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 5:05:57 pm

Hi Jeremy-
I did exactly as you said- loaded the 29.97 cam file first, added the 30 clip, selected it, retimed for auto speed, set it for the (custom) exact length of the 29.97 piece.

now instead of the top clip (the iphone clip) being a little too long, now it's a little too short. you can see it in this screen shot:

http://www.rayjuniorshow.com/stockpile/pix/fcp-weird.jpg

as you can see the mouse cursor is hovering where it says the time is 16:23:22 - which is exactly what i set the top (iphone) clip for. it should be the exact same length shouldn't it?

also, the audio is now COMPLETELY off! before it was just slightly off


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 5:25:18 pm

Thanks for the picture.

Do the clips start and end at the exact same time and are the same length?


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Ray Junior
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 5:28:42 pm

The raw footage does not, but the clips KINDA do. here's what I mean:

We used an old school clap board so I created a marker at the correct moment in both clips, then cut off the video prior to those intro markers. so they started at the exact same place on the timeline.

then, at the end, i found an identical moment in both clips and marked it in both, and cut off any trailing video.

so while they both started in the same place, and both contained the exact same material, the iphone clip was a little longer.

then i applied the changes you suggested and the iphone clip ended up a little shorter instead.

I muted the audio on the iphone clip (the better audio is from the other camera) and at it's just as it was before in one respect: the audio at the beginning is pretty much in sync, but by the time you get to the end its out of sync.

however, now its even worse - its WAY out of sync.

so i'm confused


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Jeremy Garchow
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 5:56:27 pm

[Ray Junior] "so i'm confused"

Yes, it's confusing.

Now, take that green retiming bar, and drag it so it's the same length as the bottom clip.

In sync?


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Ray Junior
Re: Audio Sync Issues In FCP
on Mar 21, 2014 at 6:01:36 pm

AND VOILA! YOU'RE A FREAKIN GENIUS!

thank you!


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