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I recorded months of video at 44.1/16 kHz should have I recorded at 48? (sync problems)

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Greg Accetta
I recorded months of video at 44.1/16 kHz should have I recorded at 48? (sync problems)
on Jan 22, 2014 at 12:39:00 am

Hello,
I am having a MAJOR issue, being new at audio I used the Zoom H4n and recorded at 44.1/16. I shot on the 5D Mark2 at 29.97 FPS. I have been told, (and I can see now) that my audio will be out of sync. I have very long interviews, and also some very quick action shots (its a sports documentary). I really don't know what to do. I've been told to just convert them in Adobe Audition, but does that just speed up the audio?
I would like the best solution, not the quickest, since this film is intended for festivals and hopefully ( a theatrical release) or at least that how I want everything to be set up. Can someone help me out on how to solve this problem? I will be editing this on adobe Premiere.


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Richard Crowley
Re: I recorded months of video at 44.1/16 kHz should have I recorded at 48? (sync problems)
on Jan 22, 2014 at 12:26:36 pm

As you have discovered, virtually all video production is done at 48K. While it would have been preferable to record your audio at 48K, recording it at 44.1K is not a show-stopping problem. Yes, you will need to convert the 44.1K audio to 48K when you edit the video. Many NLE applications do this for you automatically. Modern software does a pretty good job of converting without any significant artifacts, especially if you are talking about only speech (and not music).

Even if you had recorded the audio at 48K, it is doubtful that it would change the sync problem. It is not reasonable to expect that mass-market audio and video/photo gear will hold sync for more than a few minutes. This is NORMAL.

NEVER attempt to adjust (stretch or shrink) the AUDIO track to match the video. ALWAYS "adjust" the video to match the audio. It should not be terribly difficult to tweak the video track forward or back to match the audio.

It sounds like you have "cut-away" or "B-roll" video that will be cut into the video of the interview subject. At each point where you do a video edit point, you have the perfect spot to "pull-up" the video track to re-synchronize it with the audio, which should be used as the "master reference track". Even if you don't have B-roll to cut to, stretching (or "shrinking") the video track will cause the NLE to cut or repeat a few frames of video to conform the length of the video to the audio. These occasional frames are much less noticeable to the average viewer (IMHO) than the possibility of damaging the audio track by trying to stretch/shrink it.

Don't sweat it, many of us have been there, done that, and have the T-shirt. You can do it.


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Greg Accetta
Re: I recorded months of video at 44.1/16 kHz should have I recorded at 48? (sync problems)
on Feb 15, 2014 at 12:32:50 am

Richard and Andrew,
thank you so much for the useful info and the piece of mind to know that its something that can be manageable.
I have a lot of stuff I shot on the fly as well too, that I will be using Plural Eyes 3 to Sync up, since it will take a very long time if i did it manually. if I sync it up using Pluraleyes (still at 44.1) and then pull it into premiere, then when I have a cut i am satisfied with i could always export it at 48k. is that possible? or something will go wrong, hypothetically if it looks all synced up.

thanks again


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Andrew Rendell
Re: I recorded months of video at 44.1/16 kHz should have I recorded at 48? (sync problems)
on Jan 25, 2014 at 12:18:02 pm

As Richard says, not holding sync between kit like that is quite normal. The conversion from 44.1kHz to 48kHz shouldn't be noticeable with modern software, it doesn't change the running time.

Did you have the camera recording it's own microphone? A camera-mounted microphone is almost entirely useless for production sound but is very useful for syncing up sound recorded on another device - in your NLE, place the camera pictures with it's sound on a timeline and add the Zoom sound immediately below it, you can then line up the waveforms. Start at the beginning and go along the track until it's out of sync and put a cut point in the Video/camera audio and slip it back into sync with the Zoom audio. Allow yourself a tolerance of half - three quarters of a frame between the tracks (you can only move the video by whole frames and very few viewers can tell if the sync is out by half a frame anyway). Once you've done that, delete the camera mic and use that timeline as your source for the editing.

My experience is that the Canon pictures and Zoom audio will usually run close enough to stay in acceptable sync for 2 or 3 minutes at a time (as a very rough rule of thumb, it could be double that, it could be half), so you should be able to put your video cut points in spaces between answers to interview questions (unless the interviewee is one who gives very long replies, but even then, everyone has to breathe occasionally and a cut in a gap to either duplicate or cut out a frame will ne less noticeable than during a word).

Don't vari-speed the video unless you really, really need to stay on it for a very long time, if you have to, use a setting that interpolates the frames rather than dropping or duplicating (i.e., FluidMotion or equivalent).


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