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Multicam edit and audio sync problem

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Davide Marchesi
Multicam edit and audio sync problem
on Feb 14, 2013 at 2:10:38 pm

Hello everyone, I know that the multicam edit workflow has been discussed extensively, but I couldn't find the specific information that would help with my problem, sorry to bother all of you and thanks again for your help.

Here's the details:
- shot a concert with 3 (different) camera all shooting HDV 1080i50 (HD1440x1080)
- imported and already synchronized the 3 video sources in a few multiclips (one for each song) they all seem to match fine
- when the audio files of the concert came in from the sound engineer i try to sync them to my multiclips, but the audio files won't match the video! (i.e., the audio file 4-minute long song ends about 10 secs before its video!)

My guess is that there is clearly something wrong with the formats (audio and video), but I would not know what it is. Here's the specifics for audio and video
Videos: 1440x1080i50, 25fps, data rate around 3.1MB/sec, audio 16-bit integer, 4khz
Audio: stereo, 44.1khz, 24-bit integer, data rate 258.4K/sec

I'm not sure if the fact that the footage is interlaced could cause the problem. I have used the multi-clip edit before, for similar jobs, synchronizing the audio just like I'm trying to do now and it always worked, but it was progressive footage most of the time.

Thanks for your help and attention


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Davide Marchesi
Re: Multicam edit and audio sync problem
on Feb 14, 2013 at 3:40:37 pm

UPDATE: doing some more research I found that the problem might not be related to the multicam edit, but due to the fact that I'm trying to sync the 48 khz audio from the camera with the 441. khz of the audio files I was given by the sound engineer.

Unfortunately, after converting the audio files from 44.1khz to 48, nothing has really changed, as you can see in this picture of my timeline:

https://www.dropbox.com/s/m3od7gsagzy38qe/sync.jpg

It is clear that the mismatch in the audio file is quite significant (I believe it gets to more than 10 secs towards the end of the song). What seems quite strange to me is that the audio doesn't seem to slowly drift away, but rather seems to just differ significantly in the interval I highlighted in the picture.


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Konstantin Voronov
Re: Multicam edit and audio sync problem
on Aug 17, 2013 at 7:35:28 pm

Hi, I have got the same problem. Did you find any good solution for this problem ?


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Davide Marchesi
Re: Multicam edit and audio sync problem
on Aug 17, 2013 at 11:54:26 pm

Hi Kostantin,

Make sure the sound from the cameras and any other sound files share the same frequency (usually 48k) and that your sequence settings are set for that same frequency and fps as the footage. If that's not the case, FCP might import the sound files with different frequency and fps and that could give you problems with the synchronization. Let me know if you have trouble.


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Konstantin Voronov
Re: Multicam edit and audio sync problem
on Aug 21, 2013 at 12:40:29 pm

You'r right. my gopro footage was made with 48k freq audio and zoom h4n audio with 44.1khz freq. But i think final cut pro X some how takes care about this itself. at least 10.0.8th version. after all i spent hours trying to figure out what was wrong and it seemed that i've tryed every suggested solution of fixing syncing 48k and 44.1 audios issue. none of them worked for me though.

So i went on until i finally found a very strange little jam on the zoom h4n record, probably the result of a writing to flash card error or some zoom h4n hiccup. After removing affected fragment i synced it again and everything was fine this time.

So for those others who will google this "sliding out of sync problem" i would recommend checking thoroughly for exact moments where it starts getting out of sync and there looking very carefully for any kind of hiccups or sound jams on any of the sources. its very hard to hear and as i got so far this could be a pretty much pain in the ass.


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