Audio and video files drift out of sync

[b mcgibney]

Hello folks

Given that there are no gigs these days I am participating in a Canadian based (but internationally participating ) group called the gig lives on.

My work flow on tunes has been to record a video track while at the same time tracking the parts (Vocals and Keyboards, so far) into Pro tools.

I then load the movie into "Photos" export to desktop and import the video into the same session I tracked the audio with.

One tune we were working on seemed to get sloppier and sloppier timing wise.

I went back into my original session file and double checked the transient of the first notes were aligned between the iPad Pro audio and the same tracks that were recorded at the same time in PT 2019.10. Imagine my surprise when I went to the end of the session and found that the video audio and the direct audio were out by about a 125 milliseconds.

Is this a frame rate issue ,the session is at 30 fps and there seems to be no rate to change it.

I'm 40 years in audio and 20 years in Pro Tools but this video thing is all new to me.

Any pointers out there?

Best

Brian

[Darryl Ramm]

The most obvious guess is the video was not recorded at 30fps but rather 29.97fps. And it's being mangled by playing back at 30 fps. ... lots of information about that difference if you Google for it. And you can calculate the offset and length of song and see if the numbers work out.

[huub]

Your video and audio recording did not have the same reference (video equivalent to wordclock).
This means there will always be some drift. The amount varies with hardware combinations, you could be lucky and have very little drift or you could have a lot of drift.
Locking everything to the same reference takes expensive equipment. (you would need a camera that can actually lock to ref for starters)

So easiest solution is to mix and then timestretch your final mix.
Or make little edits in audio or video every once in a while.

Huub