Problem with overlaying audio on footage - possible reasons?

[The Beatsmith]

Hi

A while back we video'd a vocalist singing/rapping over a piece of music that was being played back off CD from a car stereo. Everything went fine there, and the footage was captured to digital tape at 25fps, with the audio set to 48khz - nothing strange there.

This tape then handled by someone else and imported using Premiere on a PC to an MPRG - which will not play back on my mac, or convert using Compressor. We had to use MPEGStreamclip to convert the footage to a prores MOV for editing etc. This seems to play back fine.

I have the original audio file that was being played off CD in the car, and it's at 48khz. The problem lies when i try to overlay the music on top of the audio captured by the camera mic - it will be in sync for a few bars then go off. If you correct it, other section will soon be off.

Could this be a tape/encoding issue? Something with the camera? It isn't a sample rate issue as far as i'm aware, because the audio is exactly the same pitch. We do not think there was audio skipping on the CD player, as it would have been noticeable.

The guy who encoded the video off the tape said they'd been having issues with stuff syncing up - as he works in Premiere and passes the stuff over to his colleague who works in Final Cut. I have no idea on the level of competence this guy has.

Does anyone have any suggestions or advice on what might be causing this, or how to remedy the situation? We just wanted to overlay the CD audio over the footage audio as it's very feint.

Could it be a frame rate thing? A key frame thing?

In the meantime, i've given the tape to someone else to try to get it re-imported using a different setup, and directly into Final Cut.

Thanks!