Multicam clip audio sync problems
I have a conference I am editing. Morning session and Afternoon session approximately 3 hours each.
I filmed on 3 cameras with split audio on camera 1 (2 XLRs with a cavalier on channel 1 and a fixed mic on channel 2)
I was able to sync the morning session (6 x 3 hour segments) using the audio sync method, but I am now running into a problem with the afternoon session. It stays in the mode "Synchronizing Multicam Clip for a long time without moving further than about the first letter "g" on the word "Synchronizing Angles" which displays underneath.
The only difference I can figure out is that on the afternoon session the speaker started talking about something related without officially starting the afternoon session, so after 6 minutes I did my slate and he started.
Could it be that because the audio slate is 6 minutes in that it is taking a longer time or does FCP use the whole waveform for synchronization without focusing on the audio slate (clapped hands)? I am dreading the manual method but I can do it - just wondering if it is a problem related to the amount of footage I have in one project, the above or something else!
Any help would be appreciated.
(I am using the trial version of Final Cut Pro X 10.2 as I am testing it out versus my usual FCP 7 Suite before purchasing)
Final Cut Pro X, OS X Yosemite (10.10.3)