Sound falling out of synch

Slimothy

Slimothy

Veteran
Got my sound back from a post house today. I put it on the timeline and everything is fine but as it goes on, it gradually gets out of synch. Do I have some kind of frame rate problem?

Tim.
 
Hey Noah,
The sound files are .wav files. The camera used was the CineAlta and the codec says it's DVCProHD

Does that help?

Tim
 
Sounds like a transfer issue. Perhaps the audio was not recorded at a matching timecode? I'd go back and check with the transfer house. You'd need them to correspond the HDCAM to DVCPROHD transfers with the audio, whereever that came from.

Noah
 
NoahK said:
Sounds like a transfer issue. Perhaps the audio was not recorded at a matching timecode? I'd go back and check with the transfer house. You'd need them to correspond the HDCAM to DVCPROHD transfers with the audio, whereever that came from.

Noah
Click to expand...

Not sure I get this Noah. I basically rendered them out a file from my timeline to do the sound from. They did the sound and sent it back, and now it's out of synch. It starts out in synch, but goes out of synch gradually as the movie goes on.

Thanks for the notes by the way.

Tim
 
It would really help a lot if you could describe the issue in much greater detail. Camera used, audio gear used to record- to which formats, how transfers were done, what format edited on/frame rates, etc where you are in the process, etc. Otherwise we're kinda guessing here.

Noah
 
Sorry about the lack of info. I'm sort of in the dark about some of it as well. I wasn't involved in the original production and I am the third editor on the project. The first editor was fired, the second didn't have time, so now I'm here. I don't know what audio gear, but the camera was the Cine Alta. When I click GET INFO on the clip it says the codec is DVCProHD 1080i60, I'm not sure if it matters, but I believe my timeline is 23.976.

I assembled the clips, then exported out a quicktime file (I think with the DV codec) to the sound designer. I also gave him an OMF w/ the sound files so he could manipulate them in Pro Tools. He gave it back to me but when I put it on the time line it starts out fine but eventually goes out of synch. I would say about a minute in you start seeing that there are slight issues w/ the synch falling off. Then as it goes on it gets more pronounced. The movie is 17 mins long so as you can imagine, by the time it gets to the end, it is at least a couple seconds off.

Hope this helps.

Tim.
 
I'd suggest you get in touch with the DP and sound recordist and find out a little more about what they shot and recorded originally. This a little like saying 'here's this pile of rubble, now what's wrong with the original building?' :zombie_smiley:

Sync issues indicate that the video and audio do not share timecode and frame rate. If I had to venture a guess I'd imagine the person who did the mix took 23.98 audio and added in a pulldown to make it 29.97 audio- so it's 20% slower than it should be. That means over time your audio gets progressively more and more out of sync. So the way to fix would be go back to the audio post person and have them re-export without adding in pulldown so it will sync up to your 23.98 timeline rather than a 29.97 reference.

This happens all the time because most post-houses expect their audio to be sunc up with a tape master not a 23.98 QuickTime edit. I suspect if you output your footage to tape with pulldown and then loaded the sound designers audio in a 29.97 timeline it would line up fine.

Noah
 
NoahK said:
I'd suggest you get in touch with the DP and sound recordist and find out a little more about what they shot and recorded originally. This a little like saying 'here's this pile of rubble, now what's wrong with the original building?' :zombie_smiley:

Sync issues indicate that the video and audio do not share timecode and frame rate. If I had to venture a guess I'd imagine the person who did the mix took 23.98 audio and added in a pulldown to make it 29.97 audio- so it's 20% slower than it should be. That means over time your audio gets progressively more and more out of sync. So the way to fix would be go back to the audio post person and have them re-export without adding in pulldown so it will sync up to your 23.98 timeline rather than a 29.97 reference.

This happens all the time because most post-houses expect their audio to be sunc up with a tape master not a 23.98 QuickTime edit. I suspect if you output your footage to tape with pulldown and then loaded the sound designers audio in a 29.97 timeline it would line up fine.

Noah
Click to expand...
Thanks Noah,
I'll try that.

Tim.
 
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