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That syncing feeling


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#1 Allyn Laing

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Posted 28 October 2006 - 12:33 AM

Hi,

I recently shot a film on 16mm at 24fps (for projection) and the sound was recorded at 25,
the film has been TC to 25fps for tape but when I sync the sound it falls off after the first few seconds, I'm sure there is an easy process to do this, can anyone give me some pointers?

Thanks heaps
Allyn

Australia
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#2 Phil Rhodes

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Posted 28 October 2006 - 06:30 AM

Hi,

The sound wasn't recorded at any frame rate, it's just sound, it has no inherent timebase characteristics. You may have used 25fps timecode, but that doesn't have any effect on the way the audio is recorded. Therefore, you've now speeded up your pictures by 1fps, but you haven't speeded up your sound; it shouldn't be any real surprise that things don't match up.

If you want to finish on tape, you have given yourself a major headache by not shooting at 25fps. You'll have to re-time the sound, which can be done reasonably well in software such as Sound Forge, and which will involve speeding it up about 4.5% (or whatever it is to make it work). If you then want to finish back to film again, you'll have to talk to your lab and figure out how they want to resolve things, as there's a number of approaches.

This is why independent productions in PAL countries invariably shoot 25fps, even if it's for cinema release - it makes post so much easier.

Phil
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#3 David Cox

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Posted 28 October 2006 - 06:38 AM

Hi,

I recently shot a film on 16mm at 24fps (for projection) and the sound was recorded at 25,
the film has been TC to 25fps for tape but when I sync the sound it falls off after the first few seconds, I'm sure there is an easy process to do this, can anyone give me some pointers?

Thanks heaps
Allyn

Australia


Hello,

The most likely problem is this. You have 25FPS timecode on your sound recording, so you have assumed you need to run your film at 25FPS to make it sync. The truth is that sound doesn't have any frames per second - it just runs the duration in runs at. The sound was recorded "real time" with the film, which was running at 24FPS. So most likely you actually need to play your transferred film back at 24FPS in order to sync with your sound. At the moment, you are playing it at 25FPS, so your sound will go out of sync at the rate of one frame per second (if my assumptions are correct).

What you do to correct this depends on your final application and specifically what frame rate you are delivering. You mentioned the film was for projection. If this is 24FPS film projection or 24FPS HD projection, then when you set your editing system to play back at 24FPS your sound should sync. If you are projecting from video at 25FPS, then you will need to correct your audio by speeding it up by 4% and pitch correcting it downwards so it doesn't sound sped up.

Hope that helps.

David Cox
www.baraka.co.uk
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#4 Rachel Oliver

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Posted 28 October 2006 - 07:16 AM

Hi;

But none of this good advice matters if you did not use a crystal sync camera in the 1st place.... :ph34r:

Olly
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#5 Allyn Laing

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Posted 29 October 2006 - 12:40 AM

The film was shot on:

Arri Sr2 and 3
Aaton LTR
Aaton minima

Its unbeliveable what i've been through to make this film happen, all for the craft hey ;)

do these cameras aply to 'crystal sync'
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#6 Rachel Oliver

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Posted 29 October 2006 - 04:44 PM

The film was shot on:

Arri Sr2 and 3
Aaton LTR
Aaton minima

do these cameras aply to 'crystal sync'


Hi;

Hell yes B)

Olly
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#7 Dominic Case

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Posted 29 October 2006 - 11:47 PM

You've done the right thing for the image in transferring to tape at 25fps. You have exactly one frame of video for every frame of film.

But playing the tape on a PAL system means that it will run 4% fast - which might make pacing the edit a little difficult. But you don't say what you are editing on. If you have a system that can play at 24fps, then all you need to do is to ingest your sound then sync it so that everything plays at 24fps - and the action will be at the correct speed.
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