Audio Syncing - What frames to use?

[butterbescotch]

I am quite curious with audio syncing. Well, we shot a footage in 23.976 frames, then we sync it with the audio from a phone recorder. Anyway, it matched.

My question is if the footage was shot at 25 or 30 or 60? Would it still matched? Or if not, will using a 23.976 sequence in premiere will compensate for it?

And what's the deal with 24 and 23.976 frames anyway?

Just wondering

 

[Will Vincent]

It would be synced if the timeline of your edit was set to the same framerate of the source footage.. but even then (and yes, even at 24/23.976fps) audio sync can shift over the length of a clip.

The deal with 24 vs 23.976:

I think this explanation from David Mullen, ASC pretty well sums it up:

For a long time, one reason for shooting at 23.976 fps was because that post was done using NTSC video transfers, so even if you shot film at 24 fps, it was transferred at 23.976 fps to video for distribution to editors at 59.94i. And generally sound editors would receive videotape copies of the offline cut and edit to that. In the end, the whole thing had to be resolved back to straight 24 fps for feature films.

And once 60 Hz countries chose to continue 59.94i for 1080 HDTV broadcast, the problem really hasn't gone away.

I did one of the first 24P HD movies on the F900, "Jackpot", in 2000 and the Sony F900 had the option of 24P or 23.98P... I chose 24P. Later I asked how the sound mix was going and the editor told me that they had to shift whole reels over slightly to get them to stop drifting in sync, so I suspect that was partly due to shooting in 24P instead of 23.98P but editing in NTSC. Of course editors can now work in true 24P and they can send that to sound editors who can work at true 24P on their systems, but for some reason, the whole chain still works using dubs in 59.94i.

 

[butterbescotch]

Thanks for the reply Will, but I'm quite confuse.

You said about "timeline of your edit was set to the same framerate of the source footage". However, the separate audio does not have a "framerate" so how can we know that the audio recorded is in 24 or 23.976, So we can prevent the small discontinuance?

Is my question valid at all? I'm quite confuse at all :/

Regarding the quotation from David, it mentioned about "NTSC Transfer". So the thing is the audio sync matters also if the timeline is in NTSC or PAL? Isn't it NTSC and PAL just a geopgraphical term for 24 Frames and 25?

Sorry for the trouble.

 

[Will Vincent]

What I'm saying is, if you recorded the video at 24fps, and set up your edit timeline for 23.976 (or vice versa) the audio certainly will drift because the video would be played back at a slightly different speed than 'real time'

If the video edit timeline is the same framerate you recorded the video in, that video should play back real time speed, so the audio should stay in sync. But even then it's entirely possible it could slip out of sync during a lengthy clip.