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Audio Sample rate for shooting on film


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#1 Bo Price

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Posted 23 October 2015 - 08:33 PM

Hey guys,

 

I'm shooting a film tomorrow and the audio guy has a good question and I don't know the answer.  

 

We're shooting on film, so 24 fps, and then I'll finish on video, so 23.97.

 

What is the proper audio fps and sample rate?  He suggested 30 fps at 48.048 khz, so during the pulldown it becomes an even 48khz.

 

I assumed since we are finishing in 23.97 and not 29.97 we shoot audio at 24 fps and 48.048.

 

But this is all confusing to me and I'm out of my element.  

 

Can anybody help? 

 

Thank you so much!

 

Bo Price

 


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#2 Satsuki Murashige

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Posted 23 October 2015 - 09:15 PM

Sound should be recording at 48.048Hz. Audio does not record in frame rates - the only reason they would need to know the base frame rate is to set their timecode properly.

If you will be telecining your film at 29.97 interlaced with a 3:2 pull down and finishing that way, then his plan could make sense. But I f you're getting your film scanned in progressive frames and thus finishing at 23.98, then it seems to me that his timecode should be set to 23.98. I could be wrong though, it's been at least 5 years since I've shot sync sound celluloid film.
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#3 Bruce Greene

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Posted 24 October 2015 - 01:21 PM

Hi Bo!

Of your camera doesn't have a crystal for 23.98 then you'll be shooting at 24.0fps.

I would think that the sound time code should match exactly the camera time code, so sound also at 24.0 fps.

If sound is at 23.98fps, and camera at 24, you will drop sync every 501 frames I believe.

I would think that sampling rate is independent of the frame rate which is used to sync sound and picture.

We've been filming sound and picture at 23.98 and converting both to 24.0 for DCP in theaters. But sound must match picture to maintain sync.
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