I have converted my video files from .MTS to ProRes (Proxy). When I play them back in QuickTime everything is fine. When I import them into Final Cut pro, they start getting out of sync with the audio at the end of the clip (they're about 20 minuts long).
I'm at a loss why this is happening. There is no problem in QuickTime. Why would there be in Final Cut Pro. Final Cut tells me that all files are 48,0KHz, 16-bit integer.