hi,

I've had this problem a few times in the past but i just decided to act upon it. When i film a wedding, for the first dance I usually have two cameras filming from 2 different points of view. One of the cameras captures the live audio with a directional mic.

When editing the first dance, I put the original track on top of the live audio and problems start. I sync the original song with the live audio and....i can definitely notice that bit by bit the two tracks get unsync!!! I sync at the end of the tracks and it is the begging that is out of sync! why?!!
Is there anything that i can do to fix this problem, it's really frustrating. I record the live track with a Canon XHA1(25f) and a Audio Terchnica directional mic.
Please help!
thanks!

What is the other camera? Are they both set up the same? 25fps on both? 44.1 or 48K for sound on both?

Cameras are not genlocked so they are each running on their own crystal. Even slight variances in their speed will end up giving you drift between the two recordings. Depending on the quality of the cameras this can take a few minutes to be noticeable or be minimal for longer takes. You should edit out the difference as you go. If you sync at the start then every 5 or 10 minutes you will want to check the drift and see how many frames you want to remove from the camera which doesn't have the soundtrack you want to use.

thanks for your replies guys.

I didn't explain properly. The out of sync problem ocurrs between the live audio track coming from the camera and the original track mp3.
This mp3 but when put on top of the 'recorded through the camera' version, they're out of sync.
Does that make any sense at all?

What is the mp3 recorded with and is it set up the same way as your camera 44.1K or 48K?

I've run into this from time to time when shooting weddings and also with dance programs. It happens with both CDs and MP3 tracks. The problem is not so much the cameras losing synch as it is with who and what are playing the CD/MP3 track while you are shooting. Wedding DJs can vary the speed of playing tracks so that they match up better when fading from one to the next and so they match better with the mood the DJ is trying to set.

I lay the MP3 track underneath the camera audio and check the synch repeatedly. Often, I can adjust the MP3/CD track by making a speed adjustment (property box for the track). For example, for the last dance recital I shot, I found that setting the track speed to 99.5% matched it up to the camera audio within a frame over 5 minutes. Sometimes, there can be a lot more work. I had a wedding last year where the bride had sent me an iTunes version of "her" song and the DJ had edited his own version for the first dance. I had to make adjustments to the downloaded music track every 30 seconds or so. Then there have been several times when I just could not get my tracks to match what was played live and had to go with the live sound.

Singular Software's Plural Eyes, the audio synching program, now has a beta version for testing with CS5. I've downloaded the beta but haven't yet tested it for this purpose. You might try download the beta and see if that helps. Here's the link:
Singular Software (http://www.singularsoftware.com/pluraleyes.html)