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Audio out of sync when imported into FCP

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Ron Dawson
Audio out of sync when imported into FCP
on Oct 7, 2010 at 12:42:50 pm

I posted previously of my issue with FCP where an XDCAM clip I transcoded from DSLR footage was getting out of sync in FCP. This is the audio contained within the clip itself (i.e. the audio captured by the camera). Everything is fine if the clip is played in the Finder. But when I play the clip in FCP in the Viewer (i.e. the part in the upper left-hand corner where you review a clip), as you get towards the end of the clip, the audio drifts further out of sync.

What made matters worse was when I dropped interview footage into the sequence, I had synched the footage by sound to the footage from the Zoom. So, prior to rendering, the footage looked in sync with the Zoom audio. But after rendering, I found that it was out of sync. Seems like the visuals you see prior to render are actually a few frames off from what actually gets rendered. (Argh!)

Based on comments from VU, CreativeCow, Twitter and Facebook, I ditched the GOP XDCAM codec and encoded the problem clip to ProRes. (XDCAM for 16 months has never been a problem but for some unknown reason it is now. Only difference I see is now I'm on Snow Leopard and QT7). That helped. But, ProRes is way too big for my current situation (and I don't have FCP7 to use ProRes LT or Proxy). So, I decided to encode to a non-MPEG GOP codec and went with DVCProHD. The files sizes are still much bigger than I'd like, but not as bad as ProRes.

Well, after taking 8.5 hours to transcoded 3.5 hours of footage to DVCProHD, guess what? The audio drift issue in FCP still happens. Audio is fine towards the beginning. But as you get towards the end of the clip, drifts further and further out of sync. The good news is that since DVDProHD doesn't have to go through the conforming process XDCAM does when rendering, the audio from my Zoom stays in sync in the sequence (so long as I sync to the visual of the slate vs. the sound of the slate).

Someone suggested I look at the playback settings in FCP preferences and see if the Frame offset was at six frames. It was. I changed it to zero. Didn't have an effect. So I changed it back to its default.

Does anyone out there have an idea what's going on? Again, the DVCProHD clips plays fine in the Finder or if I open it in QT. But, once in FCP, the drift happens.

Thanks.

I'm using FCP 6.0.6
Snow Leopard 10.6
Transcoded using MPEG streamclip to DVCProHD
FPS 23.98
-----

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***


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Glen Montgomery
Re: Audio out of sync when imported into FCP
on Oct 7, 2010 at 5:36:58 pm

When transcoding the footage, did you set audio to 48KHz rather than 44KHz. I have heard of fcp audio drift from a couple reliable sources and they have attributed this as one fo the causes. Might be worth a bit of google searching on audio drift. Thats all I got. Good Luck.

Editor / Motion Graphics Artist
http://www.GlenMontgomeryIII.com


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Noah Kadner
Re: Audio out of sync when imported into FCP
on Oct 8, 2010 at 12:12:10 am

I'd get a bigger hard drive- you can get 1TB for $100-200 these days. You're taking a major quality hit by transcoding to a format like DVCPROHD vs. ProRes. It's a short term gain for a big loss.

Noah

Unlock the secrets of 24p, HD and Final Cut Studio with Call Box Training. Featuring the Canon 5D Mark II and 7D.


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Ron Dawson
Re: Audio out of sync when imported into FCP
on Oct 11, 2010 at 3:25:19 pm

It's an economics issue Noah. The majority of projects I produce go to web 640x360. Maybe they'll be played once at a corporate event on a computer from an HD QT file or a SD DVD. I do a lot of grading with Magci Bullet and by the time I add all the other filters, music, etc, the end product is great for the delivery and distribution purposes of my clients.

If I do a project that goes to broadcast, or some other kind of distribution channel that requires the quality of ProRes, I'll do it. But, even at $100/TB (which is great), the amount of TB drives I'd have to purchase would add up quick.

FWIW, I will plan to start using ProRes LT and Proxy.


Anyway, the codec is not the reason for the audio drift I'm getting. I wish it would've been that simple.

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***


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Michael Gissing
Re: Audio out of sync when imported into FCP
on Oct 8, 2010 at 6:26:51 am

[Glen Montgomery] "did you set audio to 48KHz rather than 44KHz"

Wrong way around. Audio in FCP should always be 48khz and the sequence set to that sample rate as well. This is the standard for broadcast digital video and the sample rate that most cameras shoot with.

If your final file is for the web it may have a different sample rate but make this change after your edit in FCP when you make the final files in Compressor.


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Ron Dawson
Re: Audio out of sync when imported into FCP
on Oct 11, 2010 at 3:19:36 pm

I always use 48k.

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***


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Ron Dawson
Re: Audio out of sync when imported into FCP
on Oct 11, 2010 at 3:26:52 pm

The latest update is that I discovered that 29.97 footage does not drift when imported into FCP. I transcoded the original h.264 files (shot at 23.98) and this time transcoded them to 29.97, and the drifting does not occur. The downside is that I don't want 29.97 footage, I want 23.98.

I would make the conclusion that 23.98 footage is the culprit, except that there are SOME 23.98 clips I have which are also fine. But, somehow the drifting seems tied to 23.98 footage. Is there some other kind of special FCP tech support out there. No one can figure this thing out. Is it just a quirky bug?

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***


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Jim Nelson
Re: Audio out of sync when imported into FCP
on Nov 17, 2010 at 2:57:47 am

I'm having the same issue but with DVX footage. I've mixed DVX footage with ProRes captured Canon 7d footage on the same timeline though. I did pulldown removal for the DVX footage at 23.98 so you're right, that could be the culprit. I just wish I knew why I've NEVER ran into this problem before.

Anyone find a solution to this yet?


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