Audio sync troubles

We were hired to video a ballet performance and master the CD accompaniment. I
have the wav files that I used to create the CD and am using that as the sound
track. We shot the production every night it was performed to gain the best
variety of shots. Now we are attempting to synchronize the audio and video - not
too difficult as there are some orchestra hits that are almost identical to a
clapboard. My problem is that the sync drifts... the video will get about 2
frames fast over the course of 3-5 minutes. I've been finding cut points every
3-5 minutes and adding 2 frames of space.

The sound guy just hit play - there was no space in between tracks. There's no
way anyone screwed with the sound track CD and managed to pause and unpause
1/15th of a second every 3-5 minutes.

I'm guessing it's some sort of timecode issue, or our cameras (both the same
model) happen to run a little fast? That seems unlikely to me.

Any ideas?

I once recorded a seminar both in camera and to a separate recording device
taking a feed directly from the camera. Now you would think that the resultant
.wav file would be in perfect sync with the camera source - but it wasn't.

There is nothing 'more accurate' about drop frame -- you either shoot drop frame
and so have numbering that follows drop frame conventions, or you don't shoot
drop frame and have numbering that counts without skipping any values.

Both are exactly as accurate, and you make the choice when you shoot, not in
post. One timecode value per frame, either way, exactly and precisely accurate.

The primary reason for different audio tracks when recording with different
devices is differing sample rates: Audio sample rates for DV are described in
terms like 48k or 32k but in fact are not exactly those numbers -- as Canon
found to its shock when it released a camcorder that was precisely those values,
and no one else'e would match up -- so a digital recorder that uses 48k may not
be using exactly the sample rate that a DV camcorder using 48k does. Jim's
solution is likely the best, though some software such as Scenalyzer Live has a
'force sync' option that can do the trick automatically in cases where you are
capturing from tape.

I would like to emphasize something to those who will have this problem in the
future. Do NOT try to correct this syncronization error by adjusting the video.
Video allows precision only to 0.03333 seconds whereas adjusting audio position
will allow precision to 0.00001 seconds (though your margin of error will likely
be closer to 0.001 seconds).

Still, adjusting the audio playback speed allows for up to hundreds of times the
accuracy in syncing audio and video versus adjusting the speed in video units.
You must first enable audio units by clicking on the fly-out triangle at the
upper right-hand corner of the timeline window or through Project-->Project
Settings-->General.

It is also helpful to use the "Rate Stretch Tool" (hotkey: X). This is
much faster than going to the "Speed/Duration" menu constantly. For my
solution, I clipped my slow audio close to its end and near a spot that would be
easy to visually match with my reference audio. Then I rate-stretched the clip
to match the reference.

Next, I rate-stretched all other tracks in my multi-track audio to match the
reference (I had recorded multiple tracks that needed be rate-stretched by the
same amount). Then, I remembered to change back to the selection tool (hotkey:
V) before extending the clips back out to their original In and Out points.

Also, when making these adjustments, the multicam source monitor may stop
working though a nested sequence is still multicam-enabled. If this happens,
simply make all your audio adjustments, select everything, and copy it to a new
sequence. Everything should be back to normal, though you will have to rename
your tracks.

Finally, if you have to stretch by a significant amount, you may need to check
the "Match audio pitch" box under the "Speed/Duration" menu.
Be advised that this will require pre-rendering before playback.

Hope this saves someone the hours I will never get back on my project... Jim, I
should have read your post a little closer.