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-   -   Film Audio (https://www.dvinfo.net/forum/open-dv-discussion/24299-film-audio.html)

Gabor Lacza April 8th, 2004 12:38 PM

Film Audio
Can someone PLEASE explain me this film - audio syncing methods !!!
As far as I understand at film shoots they use a separate audio recorder for sound for example a DAT machine.
The film runs in the camera at 24fps. What is the "fps" or speed of the DAT audio ?? I read that the correct frame rate for recording audio that will be synced to film is 30 fps regardless that the film speed is 24fps because the audio does not have to correspond to the film speed but rather to the video speed since editing will be done in video .
So what if I want edit at 24fps ? And than I want the final movie to be mastered at 24 fps but also make a 25fps PAL version and a 29.97 fps NTSC version....!
Somebody please help me to understand this...
Thanks a million

Rob Belics April 8th, 2004 01:14 PM


My grandparents are from Budapest. Which makes us brothers ;)

I'm not an audio guy and I go through periods of forgetfulness but with DAT they record at 29.97 if they intend to edit on a computer because the transfer to video will slow the audio down during the transfer and it winds up being 24fps.

If you intend to edit at 24fps does that mean you're using an edit table like KEM? In which case it doesn't matter as long as you use a clapper.

Gabor Lacza April 8th, 2004 07:20 PM

Still ???
Hi Brother.....
Thansk for the quick answer but it is still unclear for me how you slow down from 29.97 fps to 24fps...You will for sure notice that in sound quality...are you sure that this is the answer ??

Rob Belics April 8th, 2004 07:58 PM

The audio is slowed down to match the film/video. Yes, you do notice the audio slow down during the editing process however when the audio is synced back up with film it gets played back at normal speed.

Like this: Since film is 24fps and video is 30fps, the film, essentially, must be slowed down to fill the full second of video but still give 24 frames in one second. Unfortunately, the audio that matches that 24 frames will also slow down. It is sometimes annoying during the edit. But during the final playback, the film will play at 24fps as will the audio and everything's back to normal.

This is part of the hell some people pay for editing on the computer and some get really screwed by it. Things have to be converted left and right and no one can drop the ball. But the ball does get dropped sometimes.

That's why I own a KEM ;)

Dale Galgozy April 9th, 2004 09:40 AM

When you transfer film to video via a Rank scanner, the audio needs to be slowed 1/10 of 1 percent because of the "pull down" of the transfer (added frames to match 24fps to 30fps).

But it is not a true 30fps (this is the 29.97 part), this is why the picture is slowed by 1/10 of 1 percent. If you transfer your film via a standard film chain multi-plexer, than no speed correction is needed.

When you edit "film" no speed correction is needed. But the audio recorder needs to run at a perfect speed, as well as the film camera.

The recorder does not need to match the "speed" of the camera.

Gabor Lacza April 9th, 2004 10:40 AM

Thanks ...but...
Thanks guys for the help trying to understand this.
BUT Dale you said when you transfer film to video...but I am not trying to transfer it let`s say to video but stay in 1080p/24 format which is not video right ?? So the 30fps audio wont match this..how this 2 will ever be sync ??
And what if i want to make a video out of this 24fps film to 30 fps or 29.97 fps...what do i do with the audio ??

Dale Galgozy April 9th, 2004 11:22 AM

Hi Gabor,

Let's start again:

1) You are shooting film right?

2) You will be transferring this film to a video format right?

3) How will you do this transfer?

4) How will you record your audio?

5) What is the end product?

6) What is your NLE system?

The only time you need to adjust the audio is when the speed of the film is adjusted. Answer question 3 first. How will you do the transfer?

Rob Belics April 9th, 2004 12:46 PM

This is what I was looking for:


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