Audio, recorded separately, strays from sync

Question

Hello,
I have three sources of media that I'm using in my project, which is a recording of a gig that my band played:
- Sony AVCHD video camera (front view), includes one video and a stereo pair
- Sony AVCHD video camera (side view), includes one video and a stereo pair
- three tracks of audio that were recorded using a separate multitrack audio recorder (Zoom R16).
I've figured out how to sync the sources together - I set an in point on a distinct piece of audio that exists in all three sources (actually it's someone coughing, I didn't think to have the drummer clap his sticks together before we started). Then I set an in point in the sequence, edited in the three sources, and adjusted the in points of the clips forward to the beginning of the set. At that point where the clips were matched up, the sources are perfectly in sync.
However, within 30 seconds before or after the sync point, some drift is evident in the audio that was captured on the R16. And a few minutes out, it's seconds off. I capture these gigs one set at a time, so we're talking about clips that are an hour long (we usually do two or three sets).
I didn't pay much attention to the detailed settings of the audio recorder before I captured the gig. Actually, I recall that the basic marketing/quickstart tutorials on the Apple website say you can pretty much use any video or audio in a single project in FCE and it would convert/transcode for you as necessary.
Had a look at the clip properties, and I see that the audio captured in the cameras is 48.0 KHz, while the R16 captured the audio at 44.1 KHz. If I'd noticed the difference beforehand I would have changed the R16's settings to match, just to be thorough - but I am a little disappointed - I'd thought that there would be compensation for differences like these... this is digital!
Could this difference in the sample rates be the problem? Regardless, can anyone suggest how I might be able to resample or convert the audio so that it doesn't drift like this?
Thanks much in advance, and cheers.

Answer 1

fudster wrote:
RyanManUtd wrote:
Hmmm ... honestly .... I am running out of ideas ...
Can I ask:
1. did you get both their starting point correct ?
2. Are the duration of both the video clips & audio clips you are trying to sync the same length ? That is, if the audio is 10 secs, then is the video also 10 secs ?
Thanks
Hey -
1. Yes, I'm certain that I matched up the in points correctly while making the edits. In the audio tracks, I zoomed in all the way so I could get sub-frame position - as described starting on pg 474 of the manual. At that point, they are in perfect sync. And as you get further away from that matched point in the sequence, the drift gets worse.
2. The length of the audio that was recorded on the cameras is exactly the same length as the video (of course). The audio clips recorded on the R16 are all exactly the same length as each other as well.
However the R16 clips are not the same length as the video clips, and the two videos are not the same length as each other. They are a few seconds different from each other, because of the way I start the recording - I step onto the stage and before we start playing, I use the infrared remote to start the recording on each of the cameras one at a time, and then I start the recording on the R16.
I don't actually know how exact clip lengths from separate recording sources could be achieved, and since I'm editing them in separately, I think it shouldn't make a different. The keyword being "shouldn't", of course. In any case, if you extend the clips all the way out to play all the available media in the track (using up all the handles), the extents of the clips in the tracks appear a few seconds different from each other, as they should.
Thanks for your suggestions, I'll keep trying to come up with something. Feel free to suggest other things you think of, I do appreciate your time and help.
I have run out of ideas ... Anyone here can help ?