Audio sync across clips in a sequence

[Mark S]

Hi All,

I've come across a sync issue I first saw last year, needing largely manual sync of a 2 hr (finished length) project. Back then I considered it an equipment issue (Panasonic Standard def output). The camera output (provided to me transcoded into h.264) would sometimes show two identical frames in succession, which I assumed was somehow related. Hopefully someone has seen this and knows a fix, because now I need to sync 50 hrs with the same 'driftlike' issue, though I havent seen duplicate frames this time.

Basically the only decent audio track of an event is recorded to a standard def Panasonic, with 2 AVCHD/AVCCAMs to sync via PluralEyes 3.5. The AVCHD includes spanned clips which seem compatible, but sync is an issue. As time goes on, the SD w/ audio seems to play longer than the HD footage, getting out of sync over time. Everything is 29.97 fps, and the same thing happened with a 5DIII previously. Audio sampling is all 48k and the frame difference over time doesn't seem to fit any frame rate, drop frame, etc explanation that I can find, so I'm stumped. Any thoughts?

Thank you!

 

[Bruce Watson]

Basically the only decent audio track of an event is recorded to a standard def Panasonic, with 2 AVCHD/AVCCAMs to sync via PluralEyes 3.5. The AVCHD includes spanned clips which seem compatible, but sync is an issue. As time goes on, the SD w/ audio seems to play longer than the HD footage, getting out of sync over time. Everything is 29.97 fps, and the same thing happened with a 5DIII previously. Audio sampling is all 48k and the frame difference over time doesn't seem to fit any frame rate, drop frame, etc explanation that I can find, so I'm stumped. Any thoughts?

Sounds like normal, expected, behavior. Different machines are... different. Drift is nearly guaranteed. And more's the pity, this kind of drift is seldom linear. The drift problem was solved early in the digital era with SMPTE timecode which forces sync during capture and makes editing easier in a timecode aware NLE (which nearly all are now). Since you don't have that, you'll be compelled to do some manual sync work. Not that hard to do, you can do it every cut if you want, but you probably won't have to do it that often.