I've shot 720p/24pn footage on the Panasonic HVX and recorded audio with an external Tascam recording device at 16bit/48khz. I then try to sync the footage with the audio in FCP using a clapped slate and aside from the clap itself, they are not even close.
I've read forums saying that the sequence settings must match the audio bitrate and they do.
I should note that the audio is a .wav file if that makes a difference.
Any thoughts on why my sound won't sync up? Any suggestions on what I might try to fix it?
Bit rate data, e.g. 16-bit or 24-bit, has no bearing on sync. Closely matching sample rates, frame rate or digital sync via time code and word clock are what determines sync.
I'm thinking there's something about the 24pn that's the problem. Might be that your camera is at 23.976 and not 24. Make a copy of your files and experiment with sample rate conversion to see if that helps.
I was never actually able to sync it up properly, but by slowing down the audio by about 10% (with a little guess and check to make it perfect) I got it to work. Luckily I had only one (very long) clip to do this on and there was no dialogue.
All that said, I'm still not sure what the actual problem was and it definitely wasn't the frame rate because 24 to 23.98 is a difference of much less than 10%.