I'm having this exact same issue. I recorded video along with a song from three different angles. So I end up with the audio track that I recorded against (from all angles) and then my 3 video tracks. ONE of the video tracks matches up with the audio perfectly, but the other two start off okay and then slowly fall behind the audio. I'm clueless. I've had to manually go in and split up the video and "resync" it myself. I'd love to figure out why this is happening.
I recorded all 3 clips the exact same way in 1440X1080 and set my Vegas project settings up to match my clip formats.

Any ideas on this would be great.

The lapel mic was sent to a digital voice recorder. The sound is very good. I sent it to Sound Forge for some "smoothing" and EQ and returned it to the timeline. I found that even my audio from the two cameras was off in places and Itoo had to split quite a bit to get the sync that I wanted. I'm glad these are short pieces or I would still be splitting and syncing....

(side note) Were your camera matching.. the same kind?
Mine are not. That probably has a lot tpo do with my problem.

Well, I'm not sure I can help.

I commonly use the "dual sound" technique when I record. Using a Edirol R-09 for the soundtrack.

My recordings are usually 50 to 60 minutes long and often I have to "tweak" the sync after 30 to 40 minutes (not sure exactly)

I'm not sure why this is. Yes, different recorders .. while all being digital .. may not be running at the *exact* same clock speed and thus may drift over time.

A couple of times I've noticed that my video seemd to skip a couple of frames. This may have been in the capture, not in the camera .. and it was so small and quick that you would not normally notice it unless the audio (which didn't skip) lost sync.

I did a project recently that used 2 cameras with 2 tapes for each camera (the event lasted longer than one hour) AND my Edriol recorder. I had to match both videos AND the audio from the Edriol .. and then re-match them for the tape change. That was fun, but it worked out very nice.

Now that you mention the capture phase from cam to HD, I think I can understand the changes. I am an audio engineer by trade (28 yrs) and my venture into video (again after 12 yrs away) has been quite fun.
Thanks for the input. I will be aware of the frame skipping... that is likely. I use a Canopus 110 with firewire. It is very good and rarely skips frames even though I have had to rely on less than pro cams and other people's footage from Africa, South America and so forth. Footage shot in the jungle on a home cam does have it's drawbacks, but it is truly real footage and well worth the time to edit and produce.
Be blessed
John

I see you are an audio engineer, as am I but I will give you the answer I was going to write anyway partly as if you've been doing it for 28 years I'm guessing you trained using analogue and learned digital 'on the job' and also partly for the benefit of others.

My thought was that the sample rates of the 2 audio sources could have been different. Digital audio should be immune from the wow & flutter of analogue tape, but syncing problems can occur. It's possible to mis-read the sample rates and play back at the 'wrong speed' like an old vinyl which hasn't happened to you here, but I have come across a situation where there has been a different mis-match and the audio has played back at the right pitch, but just too fast or too slow and the difference between 44.1KHz and 48 KHz isn't huge so it would be possible to not notice it. Vegas should be able to handle different sample rates, but I'd check the properties of your audio files and resample if necessary.

Hope that makes sense!