I was editing an hour+ long performance video in FCPX using audio from both an audience mic into a camera, and audio from the front-of-house board recorded on a Tascam DR-40. I synced everything with PluralEyes, but I noticed an echo toward the end. Zooming in to the waveforms I could see that the two audio tracks were in sync at the beginning, but slightly out of sync after an hour.
I couldn’t find a way to change the speed of the Tascam track in FCPX. In FCP7 there’s a Change Speed feature where you can input the percentage or duration change down to 3 decimal points. I searched the forums and blogs and it looks like FCPX can’t do it.
I went back to FCP7 and re-synced everything there. Zooming in tight to the waveforms and using Modify: Change Speed (command + J) I adjusted the speed of the track with trial & error until it matched up. Speed change was 100.008 percent.
Out of curiosity I ran a test with a Sony HDR-AX2000 camera, a Zoom H4n and the Tascam DR-40. I found that the Tascam track was 9 frames slower than the audio from my camera after one hour.
Interestingly, the Zoom H4n was 2 frames off too, so eventually it would also need to be adjusted. But at one hour the sync difference was not noticeable.
I went to Change Speed and entered 100.008 %, re-synced at the beginning and got the Tascam track to within 1/2 frame.
Interestingly, I couldn’t change the speed of the Zoom track less than 100.005%, so it couldn’t be improved.
So for sequences of less than 15 minutes or so the Tascam should be ok, but for long form shoots (which I do a lot of) it’s kind of a pain. As much as I like the DR-40 (for the line/mic switch, the locking XLRs, and light weight) I think I’ll have to get rid of it and stick with the Zoom H4n.