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How do I properly line up audio waveforms to a clapper?

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Tim Young
How do I properly line up audio waveforms to a clapper?
on Jan 22, 2009 at 8:17:51 am

OK, so we are working on a project and figured out how to do sub-frame audio editing because the boom isn't exactly lining up with the video. But this has lead to an argument where the waveform should be properly placed.

So in FCP if I look at my time line of 24fps and I am looking at a frame just before the clapper hits and I go to the next frame where the clapper has hit, where exactly should I line up the audio waveform?

Does the tip of the audio waveform line up with what my eye sees as being the frame the sound has happened? Or do I move the waveform forward a small fraction so that the sound has taken place in between frames where the clapper would have hit if we were shooting faster than 24fps?

I hope I have worded this to make sense. Thanks in advance!



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Brian Reynolds
Re: How do I properly line up audio waveforms to a clapper?
on Jan 23, 2009 at 9:26:01 am

Tim,
Line up the audio wave form to the first frame of video that has the clapper board fully closed.
Dont worry about subframes you will waste to much time even thinking about it, as you wont pick the difference in a moving video.
Often i use a double clapperboard one at the start and one at the end of the segment (with the board upside down) this then aligns the start and end with the video and therefore everything in between will be in sync, and that way you don't have to watch the segment carefully for possible drift.



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JC Boulay
Re: How do I properly line up audio waveforms to a clapper?
on Jan 23, 2009 at 5:26:47 pm

In general, whenever you have to line up a sound with an event that happens between two video frames, you should place the sound on the frame where the event has already happened. It will look more natural, as sound travels slower than light and so every sound we hear in our life is late relative to the visual source, at a rate of 1 millisecond per foot separating us from the source.

In three words: What Brian said.

JC Boulay
Audio Z
Montreal, Canada
http://www.audioz.com


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Tim Young
Re: How do I properly line up audio waveforms to a clapper?
on Jan 23, 2009 at 5:39:04 pm

Thanks for all of the feedback. This has been an ongoing discussion here for us and the advice has been very helpful.

Tim



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