-
Crazy Sound Mix Sync Issue!
Hey Everyone!
I’m going totally insane with this sound mix, going back and forth with the mixer trying to figure out why our mix stems from the pro-tools session do not sync with our picture…
We are cutting a DVCPro HD 720p24 project. I delivered the sound mixer an OMF and a full-resolution HD Quicktime reference with TC burn-in that matched the sequence 23.98 timecode. When the mix is imported, it is too long to the picture and slowly slips out of sync, being almost 5 seconds behind by the end of the 78 minute film.
Length of the video in FCP:
In a DVCPro HD 720p24 (23.98) sequence: 78:18:17
In a DV NTSC (29.97) Drop Frame sequence: 78:23;13Length of the Sound Mix when imported into in FCP:
In a DVCPro HD 720p24 (23.98) sequence: 78:23:10
In a DV NTSC 29.97 Drop Frame sequence: 78:28;03Possible Clues:
The closest match we have is the DV NTSC 29.97 drop frame sequence of the video (reflecting real time) which is 78:23;13 and the length of the sound mix in a 23.98 sequence 78:23:10, a difference of 3 frames, which can probably be accounted for if these 3 frames are in fact frames that are “dropped.”
When in a real time (drop-frame) sequence, the sound mix is longer than the actual film by 4;20. In a strange twist, when opened in iTunes, the mix is 78:24 (it doesn’t show frames), which seems like it would match the picture in real time.
It seems to me that the mix is, in fact, probably correct to the picture in the real world. If you played the video on the computer, and played the mix separately from another computer with itunes or from pro-tools simultaneously they would sync up. But when this same mix file is imported into FCP and placed into a 23.98 sequence, it becomes too long. How could that be?
It is possible that the mix has too many “frames” so that played in real time it seems fine, but when forced into a 23.98 cadence, it gets stretched? The same way 24 frames of film becomes slow motion when played at 18 frames per second when the action is the same? Does this have to do with sample rate? I checked, and we’re at 48k across the board.
I’m not sure what the next step might be, but I’d appreciate any clues if anyone has come across anything like this before. I’ve delivered several projects in exactly the same manner and never had a sync issue when lining the mix back up.
-K.
-
6 Replies
-
One issue with syncing, is that you are putting it into a 29.97 drop frame sequence, and 24p is always non-drop frame. Usually if your mixer can’t accept 24p omfs, they’ll tell you in advance so I’ll assume that’s not the issue. Are you syncing to a 2 pop? Since your mixer will be working in audio units, and Final Cut is working by frames, that could account for slight sync offset, but certainly not a drift.
Have you talked to your mixer about it?
Richard Sanchez
North Hollywood, CA“We are the facilitators of our own creative evolution.” – Bill Hicks
-
Hey Richard,
Thanks for writing. Yes I’ve been back and forth with the mixer and neither of us can figure out whats going on. His pro-tools session was 23.98 as was the quicktime I gave him that he used in the session. It was also the editing time base, so in theory it should all match up. I only put the files into a 29.97 drop frame sequence to check against real time, since 23.98 timecode will always be slow to real time. There is a 2-pop at the head and a tail pop as well. I can tell the sync drifts because the 2-pop lines up but the tail pop does not (in addition to the obvious out of sync dialog in the film). Any clues?
-
Frsit, I hope the pro tools session was 23.976 and not 23.98. When FCP says 23.98, it really means 23.976
Another thing is to put FCP in a 23.98 easy setup (such as your DVCPro HD 23.98 setup). Then Save and Quit FCP and then reopen FCP, then reimport your audio.
Is it in sync now?
Jeremy
-
I was just searching the good ole internet with a similar issue, were reconnecting an older project for foreign deliverables and the master mixes weren’t lining up to the old locked timeline when trying to reconnect. Couldn’t figure it out, none of the files changed. I came across your post Jeremy, ran the appropriate easy setup and retried with complete success. Turns out the last project i was working on was in true 24p and this one is 23.976 and the switch fixed the audio import.
I can’t thank you enough Jeremy (if you read this, this post is over a year old!).
Can anyone tell me why this matters, is it someway the fcp interprets the audio on import regardless of the audio’s imbedded properties? And why didn’t this affect the video reconnect as well?
Crazy QT, always messing with my head!
Thanks in advance,
~Thom“This is post, you can’t fix it after this.”
-
Glad it helped!
[Thom Obarski] “Can anyone tell me why this matters, is it someway the fcp interprets the audio on import regardless of the audio’s imbedded properties?”
It seems to be some sort of frame rate flag that FCP puts on the audio. it’s strange as FCP usually doesn’t work like this, but in this case it does.
Jeremy
-
Even more issues resolving from being quicktime dependent, lovely…it’s stuff like this i won’t miss if/when apple takes a cue from the adobe guys and switches to a resolution independent interface.
*sigh*
Until that day, thanks Jeremy!
~T“This is post, you can’t fix it after this.”
Reply to this Discussion! Login or Sign Up