First, convert the mp3 audio to Linear PCM, 48k, 16 or 24 bit. That’s the audio format FCP wants to see. Then follow Jeremy Garchow’s advice,
“First, delete the new mix out of FCP and your timeline. Set FCP up in a 23.98 easy setup, then quit FCP. Now reopen FCP and reimport your new mix. The file should be in sync.”
John
MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.8 QT7.6.4 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24″ TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.3, Motion 4.0.3, Comp 3.5.3, DVDSP 4.2.2, Color 1.5.3)
Pro Tools HD w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN