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Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP

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Rodd Smith
Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP
on Jul 8, 2012 at 6:00:47 am

Guys, really need some input on this. Have gone through quite a few forum discussions but can’t nail the problem. Please help out since this is sort of urgent.

Our main objective
We have to submit for the Creation of a DCP (for theatrical projection)
What the DCP people require: DPX Log files(Video at 24fps & Audio at 48Khz)

What we did so far
We shot with the 7D/5D(1920/1080) at 23.976 fps. Recorded Audio at 23.976(sync-ed) with Video and 48Khz. We have Sound Mono wav. files at 48Khz playing at 23.976fps in sync.

Conformed in Cinema Tools
We took those Video/Audio files into Cinema Tools and Conformed them TO 24fps. The output we got was 48.048Khz playing at true 24fps Video. Imported this file into a FCP true 24fps time line and the video is in sync.

What we want
For DCP requirement, audio files to be converted FROM 48.048Khz TO 48Khz to be in sync with a TRUE 24fps time line.

The Problem
When we bring the conformed file (24FPS/48.048Khz) into the FCP timeline(sequence settings at 48Khz & 24fps), the video and audio is IN sync. However when I try and do a sample rate conversion of the this audio file from 48.048Khz to 48.000Khz and import into FCP 24fps time line the audio goes OUT of sync or drifting.
I have also tried an audio pull down 0.1% by exporting the audio into sound track pro then importing into FCP 24fps timeline and even this does not work.

Questions
1. I would like to know if there is a way to convert the 23.976fps/ 48.000khz mono files mixed out of logic pro to true 24fps/ 48.000Khz and the audio files be IN sync with a true24fps FCP time line.
2. How do we again conform 48.048Khz to 48Khz without ‘speed-drifting’ when we import the audio in the true 24fps FCP timeline?



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Ty Ford
Re: Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP
on Jul 8, 2012 at 2:08:28 pm

Hello Rod and welcome to the Cow Audio Forum.

1. Sorry for your pain.

2. You did a great job in explaining your situation.

3. I don't know.

4. Try using Wave Agent http://www.sounddevices.com/products/waveagent.htm on a COPY of your files and a COPY of your production. (or small section that you can undo) You can use it to change the header information of each file.

5. There's also Virtual Katy. It costs, but it does more. http://www.virtualkaty.com/ I have not used it.

Please let us know here if this works or not so those who come upon the thread later can benefit from your effort.

Regards,

Ty Ford
Cow Audio Forum Leader


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Richard Crowley
Re: Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP
on Jul 8, 2012 at 6:48:26 pm

Can you not simply render your 23.976 timeline as-is and just call it "24 FPS"? The difference is 1/10 of 1 percent (3.6 seconds per hour) Unless you need something pitch-perfect (people will be playing live musical instruments in sync) or time-perfect (to fit a broadcast slot), is this really a big problem? Can you not just diddle the DPX header numbers?


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Peter Groom
Re: Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP
on Jul 8, 2012 at 8:59:41 pm

Hi
Its a while since I had to do this so Im going to hesitate before saying too much. I think that JC may be better placed to comment as he has knowklege in this area.
what i will sayis

1) look at this link. It will give you the lowdown and accurate figures for pull up and pull down. http://www.ptdudes.com/2009/05/18/audio-pull-updown/

2) Id only consider Pro tools for this task.
3) Id not think FCP is good to have in the loop either.
4) Id steongly suggest you take this taksk to a post house with specific regular experience of the territory. It si a minefield and the blame will come back on you when the losses mount!

Peter

Post Production Dubbing Mixer


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Rodd Smith
Re: Audio-Post Problem – Conforming (from 23.976) to 24 fps for DCP
on Jul 9, 2012 at 4:54:36 am

Thanks a ton for your response guys.

But before we could look into that, we tried this and seems like it's working. Fingers crossed.

1. Created a Logic Pro project with 24fps/48Khz settings.
2. Took the 24fps/48.048Khz Conformed Audio/Video file and imported both into the new Logic Pro project.
3. Then Bounced this Audio out.
4. Then tried to Sync this Audio with the DPX Log files in Adobe AE.

This seems to be in sync and IN 48Khz.

Ty, one of our team did mention WaveAgent and maybe we'll look into that to check options.
Peter, yes we did take FCP out of the loop. I think FCP seems to have these frame rate/audio sample rate issues.
And Richard, need to look into the Header info change method.
Once again, thanks guys. But will let you know how the entire process goes.



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