Sync Issue  

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bencarlin
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Sync Issue

by bencarlin » Sun Aug 03, 2014 11:12 pm

Hi all,

Been working on this clip all day and I just can't seem to get the sync to work between the tree tops on one camera and another (towards shore on the right). I assume that my camera pointing towards the sky is out of whack, however bumping the starting point of that camera back and forth has yet to provide any satisfying results. If anyone has any suggestions I would greatly appreciate the help.

http://eyes.kolor.com/en/v/781aefc8a8ef ... 1a9800aee7

Cheers,

Ben

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martin.arnoux
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Re: Sync Issue

by martin.arnoux » Mon Aug 04, 2014 7:47 am

Hi Ben,

Which method did you use for synchronization? And what camera are you using?

If you are using the last GoPro (Hero 3+ Black Ed.), the best way to synchronize them is the sound: make a clap once all cameras are recording.

So if you have a "clap" somewhere in your sequence, place your current time cursor around this clap and compute sound synchronization with a sufficient research interval. Same thing if you have a some fast rotation moves somewhere. The last option is going frame by frame with the synchronization window.

Sometimes the rolling shutter of the camera, particularly in very bright light environment produce a sensation of de-synchronization but I don't think this is what we see here.

Nice video by the way!

Cheers,

Martin

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bencarlin
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Re: Sync Issue

by bencarlin » Mon Aug 04, 2014 2:14 pm

Hi Martin,

I'm using the 6x Hero3+ Black with the Freedom rig. I did both a motion sync and audio sync and neither produced a suitable result, unfortunately. That bottom left camera is always well behind the others, and the sky is very difficult to match perfectly. I think this might actually be a rolling shutter issue, as I just can not find the sync. Despite using ND filters on the day, it was a very bright afternoon and that might just have sealed my fate.

Perhaps it would be a good option to have available an audio waveform from each camera to sync the peaks of the clap?

Thanks for the feedback!

Ben

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captain3d
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Re: Sync Issue

by captain3d » Mon Aug 04, 2014 8:25 pm

I have found that AVP audio sync is not very consistent and spinning the cameras does not always give you motion data in the sky. The only reliable method I have found is to use another program (After Effects) that can display all the waveforms and let me manually sync them. Then I can write down all the frame offsets and manually input them for AVP.

Some times a flash sync works out as a visual cue

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martin.arnoux
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Re: Sync Issue

by martin.arnoux » Tue Aug 05, 2014 9:03 am

I've always managed to synchronize GoPro 3+ Black Ed. with a hand clap while every camera were recording. You can make several of them, and be sure that they are loud enough.
Then when you are in AVP, do not select a too large search range (8 seconds are enough), place the main time cursor around your clap(s) and compute audio sync.

You can't rely on environmental noise to synchronize your videos.

As you said, the motion is not accurate when one of the camera is not capturing any detail.

Martin

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Joergen Geerds
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Re: Sync Issue

by Joergen Geerds » Tue Aug 05, 2014 2:41 pm

AVP does give a pretty good sync result most of the time. there are rare occasions where round to the next frame gets misinterpreted. in those cases, watch the preview, and manually nudge the offending video/camera one frame up or down until you are satisfied. it is also super important to turn off the low-light feature (hero3+), and to use a frame rate that is appropriate for the motion you are recording.

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captain3d
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Re: Sync Issue

by captain3d » Tue Aug 05, 2014 8:47 pm

I have still had fails with good hand claps that are easily seen in the audio wave. Not sure why.


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