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Zoom H4N audio slipping-rerendering doesn’t seem to work
I know this has been discussed here and in other forums, but I recorded audio for a roughly 3 hour event (two of them, actually), with a Zoom H4N at 44.1khz. I noticed it slipping out of synch about half way through each video, so I saw that someone had posted to open the audio in a new project, set the project audio to 48khz, and render to a wav pcm audio file at 48khz. I’ve tried that, and the audio still goes out of synch with the video sometime after the first hour.
I compared the wave forms of the raw file and my re-rendered version, and they only seem different in space on the timeline by half a fraction of a frame. I realize I can go through the video and manually adjust it each time it goes out of synch, but with six hours of video, I’d like to avoid this. Is there a way to deal with this that doesn’t involve looking at nearly all my footage?
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6 Replies
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Re-rendering the audio is unlikely to make any/much difference. The problem is that the clock rates (and hence sample or frame rates) are very slightly different between the video camera(s) and H4N. Vegas has to assume that they really are the exact same rate, so you end up with one of them slightly longer. Dave haynie described the problem in https://forums.creativecow.net/thread/24/934755
You could try syncing the main video and the H4N audio in a new Vegas project, using the audio stretch to bring the start and end of the audio into sync, then nest that in your real project so that you can cut and edit as desired. This may affect the audio quality slightly but probably unnoticeably.
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I was reluctant to try that since it’s kind of an unknown quantity to me. I guess I’ll just go through it and try to listen for all the slips. Thanks.
http://www.scenethroughglass.com
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The ideal method involves a camera that ran continuously so that you have a timing reference.
Drop this camera video on your timeline and place a marker at the end of the event.
Drop the audio from your Zoom recorder on a separate audio track.
Make sure both audio tracks line up at the beginning of the event.
Zoom in to the end of the timeline.
Place your cursor at the end of the Zoom track, hold down the Ctrl key and drag it out until it matches the length of the camera audio track.
As Matt said, the timing difference shouldn’t be that big to be noticeable or objectionable. -
Thanks Mike. It will be a little bit of a pain/confusing because I didn’t slate anything, so the first thing I set to record was the Zoom. So I’ll have to find the end point (I have my beginning in sync, which works until the first hour or so ends). But I’ll try it and see how it works.
http://www.scenethroughglass.com
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Angelo, I’ve never had to try this technique myself but have read several posts of people who have and they have all said that it works very well.
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Thanks, Mike. It wasn’t as hard as I thought-even though the length of the audio for each track wasn’t the same because after the event I was going to each camera and the Zoom H4N one by one and turning them off, I just found a spot very close to the end so that I could shorten the Zoom track to right after that spot, and then I changed the speed of the clip to match the other tracks and brought the track length back to where it belonged. That saved me hours of work.
Now, if only there was anything I could do about the sound guy who left for about two hours (which I didn’t find out about until the other day), which probably accounts for why a good amount of the audio from the Zoom sounds…well, messed up.
http://www.scenethroughglass.com
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