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Losing Sync with 5DM2 footage

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Angel Nieves
Losing Sync with 5DM2 footage
on Apr 6, 2010 at 10:17:04 pm

I'm losing sync with footage from the Canon 5D Mark 2. I shot it with the previous firmware, which only shot at 30fps. Now its slipping out of sync after about a minute. Anyone familiar with this problem, and know the solution? Thanks.


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Jeremy Garchow
Re: Losing Sync with 5DM2 footage
on Apr 7, 2010 at 2:54:30 am

There's a multitude of reasons that this might happen. Please tell us what you did to get the footage in to FCP.


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Angel Nieves
Re: Losing Sync with 5DM2 footage
on Apr 7, 2010 at 3:44:25 am

I recorded the sound externally with a double system. The footage was saved on a drive, and was converted to ProRes. I didn't change the frame rate, left it at 30fps. The external audio slips out of sync by about 1 minute.

I slowed down the audio to approximately 99.94% (depending on the clip), and it stays in sync. The pitch changes by a minuscule amount (almost imperceptible). I can go this route, but eventually I'll have to convert to 29.97, and I'm not sure what problems slowing down the audio will create when I convert.


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Bouke Vahl
Re: Losing Sync with 5DM2 footage
on Apr 7, 2010 at 8:42:55 am

Sounds like the soundguy knew what you were going to do and flagged his sound to match 29.97.
(Pro recorders can do so, they just stamp a'wrong' SR in the file.)

Have a close look at the sample rate in an audio editor.
I bet it ain't 48K

So, do a test, convert to 29.97 and see what happens then.
Or, contact the sound guy, he'll know what's good for you.


Bouke

http://www.videotoolshed.com/
smart tools for video pros


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Angel Nieves
Re: Losing Sync with 5DM2 footage
on Apr 7, 2010 at 10:45:38 pm

You're right, Bouke. The audio is not 48K, but 44.1K. What should I do now?


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Bouke Vahl
Re: Losing Sync with 5DM2 footage
on Apr 8, 2010 at 9:02:08 am

No, i was NOT right.
I was thinking you had 48 Khz files, with a small adaption to compensate for speed.
You have files from a totally different recorder.
No soundrecorder for video records at 44.1

My take is that the drift comes from inaccuracy of the recorder.

So you have solved your problem yourself. Change the pitch to match and be done with it.
(oh, and since you're going from 30 to 29.97, be prepared to do it again when you make that step...)




Bouke

http://www.videotoolshed.com/
smart tools for video pros


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gary adcock
Re: Losing Sync with 5DM2 footage
on Apr 8, 2010 at 2:07:16 pm

[Bouke Vahl] "No soundrecorder for video records at 44.1 "

That would not me be my experience, that is a default for some avid workflows, so it should just be a setting change on the recorder.

"My take is that the drift comes from inaccuracy of the recorder. "

My guess is that you have gaps or holes in your timeline and since the audio has to be rendered to playback, every time you hit a gap, the render engine jumps to the next clip to render, so gradually the audio is taking longer to process then the video is

Render the timeline as an audio only "Item Level Mixdown" to see if that fixes the situation.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows for the Digitally Inclined
Chicago, IL

http://blogs.creativecow.net/24640



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Jeremy Garchow
Re: Losing Sync with 5DM2 footage
on Apr 8, 2010 at 4:29:57 pm

Did you try making a new project and using the 30.0 easy setup? You must quit FCP after you set it up, then reopen FCP, THEN reimport your audio.

What happens is whatever easy setup your project is in when you import the audio is how the audio gets 'tagged', no matter what 'frame rate' it was recorded with. There's no way to change this tag except with the method above.

Jeremy


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Angel Nieves
Re: Losing Sync with 5DM2 footage
on Apr 9, 2010 at 3:17:35 am

Thanks, Jeremy! Your solution worked perfectly! I'm in perfect sync now! Good job!


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Jeremy Garchow
Re: Losing Sync with 5DM2 footage
on Apr 7, 2010 at 1:42:15 pm

Ok, this is very important.

Delete your audio out of your project. Then choose a true 30.0 fps easy setup. Then quit FCP, now reopen FCP. Reimport your audio. Is it in sync now?


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