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Sound Editor having sync problems with my 23.98 OMF.
For the sound editor, I exported my OMF at 23.98 fps as well as a quicktime file for reference. The sound editor doesn’t have an option to work in 23.98 (which is the settings I use). He can work at 24 fps. We did a test days ago with a pop at the start and end of 2 minutes and it was in sync when I cut it into my picture on FCP. Again, he did his pop test at 24 fps and it sync up with my 23.98 fps timeline.
Well the sound editor began editing the sound, sent me a copy to import in my timeline. Results, out of sync by about 5 frames. Didn’t have the time to see if it drifted but it seemed to go in and out of sync.
What should we do to correct this? This is a HD music video where the lip sync is very important.
Also take into account that I will have to downconvert this to NTSC for DVD. Not sure if this is another issue to deal with concerning the audio.
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12 Replies
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5 frames over what duration? Have you tried varispeeding the mix file .1% (ie from 48khz to 47.952khz)?
I suspect it is the difference between 24 and 23.98 which a simple varispeed will fix. If correct, it will then be pitch correct when it is back in sync.
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I’m not an audio guy so sorry if this sounds stupid. The sample rate effects the speed of the audio? If that is the case, does it matter what fps the sound editor is working on?
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>>The sample rate effects the speed of the audio?
Effectively yes. If you take an aif file @ 48khz and slow it down to 47.952, it runs .1% slower. I suspect your sound post people, working at 24 fps are speeding up the program by that .1% . Slowing the mix down by that ratio should correct sound. Calculate the frame drift over time and see if it comes to +.1% . It is my best guess for the sync drift and it hopefully is a simple fix.
Ask you audio guys if they can provide a mix file varisped down the .1%
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I thought the sample rate was just for quality. But I’ll let my sound guy try this. Thanks.
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Have him mix in a 29.97 timeline. It’ll run the correct rate for your 23.98, and then you won’t have these hassles and worries.
you’ll have to get him a 29.97 quicktime. But I think it’s worth the sleep.
Also quickly take your audio file, do a speed change to 99.91% and see if it syncs.
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Ok, but if my footage is at 23.98 tapeless HD, how do I go about converting my cut to 29.97 fps for that quicktime output?
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Same way you would for any 23.98 material: add 3:2 pulldown. Or you could export it with a 30fps setting and FCP will just replicate frames to simulate the 3:2. Or do a setting in compressor with the mix house’s specs but have it convert to 30fps.
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Ok, I’ll try to make this happen tonight. Question, since the video will not be 100% accurate with the duplicate/replicate frames, will that be an issue for the sound editor as he syncs to action? Or is this something not to worry about?
And I should make this 29.97 NDFTC, correct? That goes for the quicktime file and OMF, correct?
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Well I’m assuming the audio is already in perfect sync in your cut. So the editor shouldn’t have to worry about it – just make it sound good. it should look perfectly fine in real-time with 29.97 picture however.
He should be able to use the same OMF from before. Just bring it into a 29.97 project.
29.97 and 23.98 are analogs of each other… both affected by the same % to resolve video rates. And since a second of audio is a second of audio, giving you an AIFF from his 29.976 project should sync perfectly with a 23.976 FCP project.
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Actually my sound editor is adding SFX and music so it’s not just cleaning things up. Thus the sync is important as he adds sound.
I created a 29.97 NDFTC quicktime file for the sound editor and handed that to him this morning. I created a timeline with those setting then copy/paste the cuts from the 23.98 timeline over to the 29.97 NDFTC timeline. After rendering I can see the difference. There are addition frames added and dropped through out the video. Doesn’t look great. The total duration changes too, going from (3:52:17 at 23.98 FPS) to (3:52:21 at 29.97 NDFTC FPS) which is a 4 frames difference.
Take note that the original video was never shot in NTSC nor on tape. This is a HD tapeless project.
So I hope this works. If I did anything wrong, please let me know. The sound editor will be working in 29.97 NDFTC and hand me the finished audio with that setting.
Thanks!
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