>>I used only one audio from all 3 cameras <<

Give us more info. How was the audio recorded? Off one of the three cameras?

I did a project with two cams recently and I took in audio from both cams and then had audio from a feed in the mixer that was recorded separatly too. I synced them up using the waveform mainly. I you use multicam in V8 it is easy to have a separate audiotrack.

I have done this in other NLE's before, but I think Vegas is far easier to sync, bacuase of the big waveform displayed.

/Ulf

I just did a multicam shoot with one camera into the soundboard, one near the stage and the other in the back of the auditorium.

I wrote down distance measurements during dress rehearsal because I wanted to have all sorts of focus presets. It was 33 meters from the stage (and speakers) to my camera in the back of the room. Sound travels at 343 meters per second at sea level, at room temperature. Thus, it takes almost three frames (33/343 * 29.97) before the sound coming from the soundboard reaches the camera in the back of the auditorium.

So, to sync, I first temporarily turned off Quantize to Frame (remember to turn it back on!!). I then pressed and held the Alt key and then slipped the audio to the left for the sound from the camera in the back of the auditorium. I started by moving it exactly three frames to the left. While I didn't have any percussive sounds, there was a steady drumbeat in one section that I then used to fine tune the result, which was just a few milliseconds one way or the other.

I then checked at the end of each recording segment to make sure that the two cameras were still in sync. They were, but if they weren't I would have then pressed and held the Ctrl key while dragging one of the sound events to the right or left to make the later waveforms line up. There are a few tricks to doing this that take too long to describe, but that's the general idea.

Now, you typically do not want to directly mix these together, because you risk getting all sorts of phasing artifacts, although the echos from the large room compared to the studio quality of the sound board will probably mask most of that. Instead, consider using a 5.1 mix, which is what I did, and use the sound from one of the secondary cameras to feed into the rear speakers, and then put only about 10% of that into the front mix (otherwise it sounds unnatural).

Anyway, people that do stage stuff for a living probably have some better ideas ...

i find 3 speedlight strbes work wel.. even a cheap party strobe light from ur local discounter works well... or maybe one of those bike strobes...

As john mentioned, sound takes time to travel, therefore u need to ensure you compensate this latency.

Usually when im syncing, i use 3 finger snaps when the cameras are abotu 30cm from each other... this gives me supertight sync BUT it also means i need to start recording sooner...

But the strobe trick works well for cameras across distances..

As for the maths behind sound latency.. sadly as accurate as people would liek to be, its not always this way considering reverberation, dispersion, dissipation and of course camera microphone sensitivity. It is imperitive to not base your entire sync on the numbers mentioned by John (sorry mate) simply because acoustic variances DO exist far more often than not

I used only one audio from all 3 cameras and I am trying to sync up the vids to the audio......
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Use the audio from the closest camera and follow Kelly's recommendations and you should be fine.

John

Wow, I wasn't expecting so much advice, thanks guys I will try your advice here shortly, I was using the audio straight from the camera in the rear. I didn't use the audio from up front because it was a small church and there was a hum that got recorded with it, from an ac unit or something and it drowned out the vocals somewhat. Hey Chienworks, you mentioned using the 4 and 6 keys to bump it frame by frame. I would guess I need to mute anything I don't want to move right? Thanks again for all the help, some advice I never would have thought of.

Umm, mute wouldn't have anything to do with nudging with the 4 & 6 keys. In fact, pressing the 4 & 6 keys will be absolutely identical to moving an event with the mouse.

Any selected events will move together. With ripple edits enabled anything following the event will move as well. So if you only want to move one event make sure it's the only one selected and ripple edits are turned off. If you want to move the video without moving the audio or vice versa you have to press U to ungroup them.

It is imperative to not base your entire sync on the numbers mentioned by John (sorry mate) simply because acoustic variances DO exist far more often than not

You are 100% correct. I was sure I put a sentence in my original post, but upon re-reading it, that sentence isn't there. If it had been, it should have said that the math calculations get you real close, but then you need to set up a loop and then slip the audio back and forth a few milliseconds until it sounds right..