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24 Frame Sync for Muliple Camera Shoots

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Dusty Powers
24 Frame Sync for Muliple Camera Shoots
on May 6, 2008 at 12:59:48 pm

Do I need to use a tri-level sync box for 23.98 multiple (2 - 3 Cam Interviews) camera HD shoots if all cameras are set are to 59.94? (Varicam and HDX-900)

Or can I daisy chain timecode with genlock as I have always done for multiple camera SD shoots?

Seems to be a bit of confusion with this. Would appreciate any feedback.

Thanks, Dusty

dusty powers
http://www.hdcrew.net



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Jesse Rosen
Re: 24 Frame Sync for Muliple Camera Shoots
on May 8, 2008 at 12:49:37 am

Do you need the cameras to be genlocked, or do you just need matching time code?

If you just need timecode, I'd skip the sync altogether and just run timecode.

If you need genlock (if you're feeding a production switcher, say), I would highly recommend using a proper sync generator and distribution amp to feed good sync to the cameras - bad sync can really ruin your day (by ruining your recordings).

--
Jesse Rosen
Director of Technical Development
Abel Cine Tech, Inc.
http://www.bustedskull.com


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john sharaf
Re: 24 Frame Sync for Muliple Camera Shoots
on May 8, 2008 at 3:49:03 pm

Jesse,

It is my understanding that the recorded video signal can also be disturbed by just daisy chaining TC (as we're all used to doing with Betacams) and that Genlock must be applied for this purpose.

I have had disrupted video both with Varicam and Cine Altas when I did as you suggest and have made it my policy to always use trilevel sync when daisy-chaining tc thereafter.

The alternative, which I've done when it was inconvenient to hook sync up (such as mobile cameras and no Lockit Boxes) is to slave the codes and drop the connection. For editorial convenience in the case of slipping code, it's also a good idea to hit sticks at the head or tail of the shot.

Some cameras, like the F900R and HDX can output the Y from the test connector and that can be daisy-chained as the sync to the next camera's genlock in connector, but I don't believe you can get that signal out of the Varicam.

This technique, and description of the problem, is taught at Varicamp by CJ and others, and confirmed empirically by my own experience, so I would be very careful in proceeding as Jesse suggests, just linking TC out to TC in. Even a short test that does work would not necessarily reveal the problem, and the resulting error, namely disrupted video, is catastrophic!

JS



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Dusty Powers
Re: 24 Frame Sync for Muliple Camera Shoots
on May 8, 2008 at 5:03:22 pm

Jesse and John:

I appreciate your input guys. Jesse, this is camera to camera, no production switcher involved.

I've always daisy chained the timecode on the betacams in the past. I've also made sure to genlock the cameras with a DA after learning this the hard way. (white clitches in the video every 10-15 seconds)I still have guys try to tell me genlock is not important. If they continue to insist then I tell other camera crew to be on the slave end of the timecode. I'll be the master and drive the timecode. They usually will change their mind at that point.

The few multiple HD camera shoots I've done were configured this same way and I've not experienced any problems. Have I been lucky with just using a small DA for distributing genlock?

Can I not do this the same way with 2 HD cameras @ 23.98 of the same flavor? Or do I need a Lockit Box or such as well for sync? And if I use a sync box what is the proper set up for the daisy chain.

I ask these questions because I'm having this question asked to me and I want to make sure it's right.

Thanks,

Dusty

Dusty Powers
http://www.hdcrew.net





dusty powers
http://www.hdcrew.net



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john sharaf
Re: 24 Frame Sync for Muliple Camera Shoots
on May 8, 2008 at 5:45:21 pm

Dusty,

Yes, DA'ing the genlock is fine, but the question then becomes: is it working? Same issue of course with simple daisy-chain too. Are all the wires functional? The only way I can figure to tell is to also patch through an HD-SDI router and notice if the switch is glitch free. On the set this is often how I notice a genlock problem.

It doesn't matter what frame rate (assuming same brand of cameras and format).

JS





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Dusty Powers
Re: 24 Frame Sync for Muliple Camera Shoots
on May 9, 2008 at 2:01:39 am

Thanks John for the confirmation.

All the best,

Dusty

dusty powers
http://www.hdcrew.net



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Jesse Rosen
Re: 24 Frame Sync for Muliple Camera Shoots
on May 9, 2008 at 1:55:17 am

Actually, I wasn't recommending daisy chaining the timecode, though I suppose I wasn't very specific. That said, I've never actually seen an image problem in a Varicam caused by bad timecode, even in testing with deliberately bad signals - as opposed to bad genlock which can very easily wreak havoc.

The safest thing really would be to just periodically jam-sync the cameras and let them freerun for a couple of hours (or less) at a time.



--
Jesse Rosen
Director of Technical Development
Abel Cine Tech, Inc.
http://www.bustedskull.com


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Kevin Layne
Re: 24 Frame Sync for Muliple Camera Shoots
on Feb 11, 2009 at 11:05:47 pm

First timer on cow...
Just shot some footage on the HDX900 at 1/2 shutter 1080 24p and then ingested into FCP thru firewire out of camera. Editor is experiencing sync slip and jitter issues. Any thoughts?



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