Head sync Pop half frame out

[mars100]

Hi all,

Here is a weird one...
So I work with Reels 24fps for feature films.Often when I receive preliminary picture cuts from Avid cutting rooms head sync pops in every reel are about half frame earlier. They should be spot on on 6th second in every reel or 9 feet.
But occasionally head sync pops are bit out. At first I thought its because whoever render them in cutting rooms wasn't precise enough, but I just had a look at the same QT in Premier Pro and head sync pop is spot on at 6sec however when imposing same QT into my PT session and extracting audio sync pop comes 0.5 frame too early.

Anyone seen this before?

Thanks,
mars

[Leverson]

You're taking about the sound from the Quicktime picture ref, right? (And not the actual AAF turnovers from Avid).

If its the former, yeah I see that all the time. Most commonly when something has been transcoded to/from H.264, but even on other QuickTime codecs. Not sure if it has something to do with the header of the file or what when Pro Tools imports it, but I simply put Pro Tools into slip mode and line the pop up exactly and now the video guide track will play properly in sync.

The video guide is just the video guide though, so I don't sweat it too much, it's just there for me to reference on occasion. If the actual turnover tracks in the AAF from the Avid are off that's a deeper problem.

[Ayush Ahuja]

+1

It always seems to be out on H264 files. Even if it's my own reference mix that has been sent back to me. Im always asking for WAV playouts nowadays so that other departments can sync correctly to it. Recently had foley that was synced incorrectly to Pfx as they used the audio from the mov.

I wish this could be fixed, I wonder if it is a Video codec bug or a ProTools bug.

[BScout]

It’s h264. It isn’t ProTools’ decoding of audio to waves. If you roll your own mp4 with h264, you’ll see/hear it happen. Made a vid with ref video and pops as an mp4 and checked back with Catch N Sync on the vid just on playback. Do it with DNxHD or ProRes, and it’s fine.

[mars100]

Hi all,

Many thanks for sharing your experience with same issue.
Yes these are QT from Premier Pro not AAF from AVID.

I also agree that these are only reference files and although its a easy fix but on every film I work I need to distribute them to various dubbing studios for dubbing sessions so it does matter to me that they are bang on in sync, especially when I don't have ready at the same time MnE /OPT/ DX stems and all other audio final masters from OV language mix stage.

Anyway..

You all were 100% correct - it's the H.264 and H.265 export from Premier Pro that for some reason puts audio files out of sync.

We run some tests today and apparently its the audio codec AAC that skews it.
We no longer going to export to H.264 but rather Pro Res - Proxy even with the penalty of having bit larger files.

Many thanks peeps!