Syncing audio to telecine'd film

[jakeboy76]

Hello all... I might just be being dense here but I'm having an issue... any help would be appreciated.

I'm editing a project that was shot on 16mm and transferred to video. During the transfer, of course, the 24fps film was pulled down to conform to the 29.97 fps of video.

The audio for this project was recorded on-set straight to disk at 48 kHz and was never given to the transfer house with the film. Now, in order to sync the audio to the video, I need to pull down the sample rate by .1 percent. Therein lies my problem: I'm unable to find a convenient way to do the sample rate conversion. If I convert to a sample rate of 47.952 kHz and then import that audio I end up having to convert back to 48 kHz, thus defeating the conversion I originally did. Thus far the only way I've figured out to pull down my audio is to a) change the duration of my audio files, or b) convert to 47.952 kHz and then use a program like HexEdit to manually change the header of the file and "tricking" DP into thinking that the file is at 48 kHz, thus effecting a slowdown of the file.

The issue I'm having seems like it would be a common one, so I'm guessing I'm missing something really obvious. What is the standard way of pulling down audio in this situation?

Thanks.

[alphajerk]

so the xfer to video slowed down the video by .1%? [or is it sped up?] why would the audio sample rate have any effect on the frame rate? shouldnt the video be time identical to the film? and the audio line up with a sync of 29.97d?

i also wonder why it wasnt kept at 24fps since FCP can edit film at true 24fps and will conform to telecine? maybe they arent using fcp.

let me know what you find out, as im interested in what happens even though i only have questions for your problem and no answers.

[chrispick]

Here's a link that may be helpful:

http://www.zerocut.com/tech/2_3_audio.html

[James Steele]

Moving this to the Post Production forum.

[chrispick]

I'm editing a project that was shot on 16mm and transferred to video.

Do you mean to say that you're picture-editing the project? Or are you editing audio with someone else's cut?

If you're the picture editor, can you not remove the pulldown, enabling yourself to work in 24fps? With any 24fps acquisition format (like film), it's best to remove 3:2 from the editorial equation.

[jakeboy76]

I am the picture editor as well as the audio editor. I haven't actually started editing picture yet - I want to deal with the audio sync issue first. The problem with removing pulldown on the video is that this project isn't going back to film, it's staying on video - so it also needs to stay at 29.97 fps.

[chrispick]

The problem with removing pulldown on the video is that this project isn't going back to film, it's staying on video - so it also needs to stay at 29.97 fps.

Does it?

Why not remove the 3:2, sync your audio to 24fps, cut picture at 24, then hold off reintroducing 3:2 until your final NTSC output? Otherwise, you're futzing with extra fields and the requisite math issues vexing you -- as well as the extra drive space they require.

Of course, I'm presuming you're cutting using an NLE app/system that works in 24fps. If you're cutting using an NTSC linear system or NLE that only handles 29.97, then yeah, you're stuck editing with pulldown video.

If not, however, ditch those redundant fields. Add 'em back later, only when you need them.

[jakeboy76]

I'm cutting using FCP. I can use Cinema Tools to remove the pulldown but to do so I need to know the pulldown cadence used during the telecine, which I don't know for certain.

This seems like a complicated way to do things. I can easily change the duration of the audio using Peak or DP to adjust for the pulldown - that seems like a much easier way of handling the situation than removing/adding pulldowns, etc. I was mostly wondering what the industry standard is of handling this - assuming that the pulldown of the video cannot be removed.

Thanks though.

[jakeboy76]

Just a thought... even if I were to remove the pulldown to edit and add it in later, I'd still be facing the same issue with the audio, no? I'd still have to slow it down to conform with the video when I went back to 29.97.

[chrispick]

...even if I were to remove the pulldown to edit and add it in later, I'd still be facing the same issue with the audio, no? I'd still have to slow it down to conform with the video when I went back to 29.97.

I think you're right.

My thinking was that whatever I/O board you use would rate-adjust both the audio and picture at output since they'd be locked (as a Quicktime with whatever I/O codec you use). This would enable you to work at 24f (or 23.976 more accurately) with 48k audio until you locked your edit. And yeah, once everything goes to 29.97 rate, everything slows down a near-inperceptible amount.

But, I've never tested this, so I'm not sure. Maybe you can test a long take or two -- see what it does?

In any case, check with these guys:

http://www.digitalfilmtree.com/

They're Hollywood FCP gurus who've assisted projects big and small (Cold Mountain, Napoleon Dynamite). They'll probably know what's what.

Sorry I couldn't be of greater help. Points for trying?

[jakeboy76]

I'm not using a hardware I/O board, I'm just outputting through Firewire, so I think that limits my options...

Anyway, you definitely get points for trying, Chris! Thanks for all your input.