Another off sync problem, this one w greenscreen
I have been working on a green screen music video for several months now, trying to get the footage to stay in sync. The client finally said forget it; he'd take the version w the green background, which I did.
But since I might want to use green screen in the future, I am not happy & want to know why it keeps going out of sync. It stays in perfect sync while in the Final Cut timeline, but once I compress it, whether in Compressor or Quicktime, (I've tried both), it starts going out of sync after about 30 seconds. I used FX Home Composite Lab Pro to do the green screen editing. And Final Cut just doesn't like it one bit. Any ideas on why this is happening and how to fix it?
Im not sure about your program but is your audio at 32K or 48K? If not at 48K you could try changing it to 48K and reimport the audio, I have had the same issues and this worked. Good Luck
Audio drift is a function of only two possible things. The audio track is on another framerate or time base or your playback system is at fault and will not or cannot handle both at the same time
How you arrive at either situation is unknown.
In the olden days, we'd see posts everyday from folks capturing Canon's weird version of "DV." The only fix was to unlink the audio from the video, find the exact length of the video track (from oepning slate to end slate, event-to-event), write that down, find the exact length of the audio track (from start event to end event, not the physical size of the track since it's the same as the the video track yet it's out of sync), apply speed adjust to it, and enter the video track's length, render the audio, relink the two tracks.
Bogie's right: we have no way of knowing the cause of the drift. We can only speculate. That said, many people like to shoot with the Canon 5D MkII, which shoots ONLY at 30fps. Such footage must be conformed to 29.97 and converted to ProRes for use in FCP.
Here's another guess: was your FCP edit timeline set for 48 kHz audio? Did you get the music for the video off a CD, which is 44.1 kHz audio? Did you bother to convert the music to 48 kHz to match your edit timeline?
But I CAN comment on the green-screen clips of yours:
In short, the sync problems are just about the least of your worries, because a cursory inspection of the resulting clips reveals that you did just about everything wrong when you shot this extravaganza. Sorry for being so blunt, but that's the way it is. As you've discovered, a little knowledge can be a dangerous thing. Doing TV & film isn't exactly the most intuitive thing one can do.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA