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converting 25fps to 23.98fps syncing issues

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Andy Oxley
converting 25fps to 23.98fps syncing issues
on Aug 20, 2012 at 10:10:24 am

I'm having a recurring nightmare with frame rates and syncing, any help would be enormously appreciated!

Me and my colleague use Panasonic GH2s, and we always shoot in 24fps. Somehow for our last shoot he was filming in 24fps and I was filming in 25 (lesson learned!) According to the forums, conforming 25fps to 24fps (or 23.98) is very straight-forward in Cinema Tools, and therefore when it comes to using Pluraleyes all should sync up as normal once in the timeline (as it does very well with our usual 24fps set up). However, the syncing with the external audio is even worse once the 25fps clip is conformed to 24fps. I realize there will be some kind of audio shift as a result of the rate change, but given that Final Cut (7.0) attributes a frame rate to the external audio once it's imported (according to whatever your sequence presets are), if the new clip is now 24fps it should sync up perfectly like the rest does.

We have a load of footage shot on this day that needs syncing, so it's really frustrating. I realize I could just spend hours manually syncing everything, but I've done this so many times I think it's about time I discovered once and for all what the problem is! I have double checked that the sequence settings match the clip settings, so it can surely only be something to do with the Cinema Tools conform?

I will be very happy to hear of any ideas!?

Andy.


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Rafael Amador
Re: converting 25fps to 23.98fps syncing issues
on Aug 20, 2012 at 12:58:12 pm

Alex,
I don't work with PluralEyes, but consider this:
When you conform 25fps to 24 fps, audio and picture are slowed down by a 4%. The audio on the will never match the audio from an external recorder or from the other camera. It will always be a drift.

I think you have to go through Compressor, to change the the video time base while keeping the audio unchanged. Then you will be able to run PluralEyes and sync.



[Andy Oxley] "I realize there will be some kind of audio shift as a result of the rate change, but given that Final Cut (7.0) attributes a frame rate to the external audio once it's imported (according to whatever your sequence presets are), if the new clip is now 24fps it should sync up perfectly like the rest does. "
That is an FC bug.FC shouldn't attribute any time-base to the audio. Audio doesn't need any time base because it has a fixed frequency: 48Khz.
And this is one issue. When you conform in CinemaTools, the video gets the time base you want, but the audio won't be 48Khz anymore. Will be 46,08Khz (-4%).
rafael

http://www.nagavideo.com


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Andy Oxley
Re: converting 25fps to 23.98fps syncing issues
on Aug 20, 2012 at 2:36:46 pm

Thanks a lot Rafael, all very interesting. I will give it a try...


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Sean Salzman
Re: converting 25fps to 23.98fps syncing issues
on Sep 27, 2013 at 4:38:28 pm

Did going through compressor work for you? i am having the same issue converting 25 to 23.98

Sean S - Editor/Post-Supervisor


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Andy Oxley
Re: converting 25fps to 23.98fps syncing issues
on Sep 28, 2013 at 11:54:49 am

Sean,
I can't say it did, to be honest. I ended up just manually chopping clips and moving them along! Whether or not there was something I wasn't doing correctly I don't know. All I'll say is that FCP7 (as I'm sure you're aware) can be very difficult when it comes to these frame rate/sequence setting issues. It's probably the one thing I don't like about it. It's not just a question of changing the setting and everything is fine, you have to change the Easy Set-Up, Audio/Video Settings, check that they match the Sequence Settings, then save it, quit FCP7, go back into it, double check the settings above, re-import the clips, and only then are you ready to get going. So it may be that using Compressor to convert/conform the frame rate does work and something along the lines of the Settings changes still made the clips misbehave for me. It was a while ago now so I may not have known what I know now. I'd be interested to know if it works for you. Good luck...


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