Video sync? NOT!

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Video sync? NOT!

Postby Doug Coulter » Sun Mar 12, 2017 1:54 pm

I did a bit of an interesting run yesterday, with a deliberate perturbation on the ion source input power, at ~ 2hz. Resulting video looks pretty neat, so I thought I'd share it. An issue that seems to have arisen (anybody know how to help with this?) is that pi cameras set at the same frame rate...aren't, at least as far as players and editors are concerned it seems.

I synced these two inside one second (this is about 45 sec worth of a longer run) at the start and by the end they are 4-5 seconds off...during the run when I'm looking at the videos in real time, those time stamps the pi puts on the screen are dead on in sync...we have a setup that flashes leds in the field of view in each at the start, and they do indeed start together, but then drift off, or so it seems. Not the greatest skill with kdenlive is demonstrated here either...so many things, just one me.
Perhaps we need a more sophisticated syncing system.
https://youtu.be/D7hL_nHTIig


Looks cool anyway...
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Video sync? NOT!

Postby Doug Coulter » Sat Mar 18, 2017 3:50 pm

By using the Vivaldi browser to get the preview videos from both cameras up on the same screen and then recording that screen locally, I found out what the issue was here.
Basically, it's the scope camera dropping frames, which it does in the preview as well - it just looks locked up, the time isn't moving. Well, it's leaving all that out of the recorded video as well.
I am not sure why, exactly; that one is on a faster raspberry pi, but also on wifi, as ground loop EMI has been an issue in that spot. So it could have stalled due to the wifi not working for a little bit when things got noisy (which of course, is exactly when we want the data the most).

I do have another switch upstairs in a direction straight away from the fusor, and a cable run to there, so at the risk of frying that switch, I'm going to try cabling that up again hardwired and see if it continues to happen. Sigh.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
 
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Joined: Wed Jul 14, 2010 8:05 pm
Location: Floyd county, VA, USA


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