What is it about the Genlock causing dropout on Video Assist?

[Steffen Vala]

Hi guys,
We're on set here with a tri-level sync genlock feed from the moco dudes that seems to be causing an irregular/sporadic drop out on the video out feed. It doesn't seem to happen when genlock is disabled in camera.

Tried to search the forum, and spoken with several folks on the phone, but maybe you guys have a quick answer?

We're in 25fps, 50hz world btw.

thanks a mil.

 

[ericyoung]

Just speculation, but if the genlock forces the camera video out to be a certain sync, but the equipment you are sending to (assuming it not just a standalone monitor, but maybe a playback system with a capture card or mixer?) is not also locked to the same genlock, then your destination is effectively freerunning with respect to your camera. This would mean that the destination equipment would slowly drift until the HD-SDI sync from the camera fell outside the sync window of the destination equipment leading to a picture interruption. It would then relock, until it drifted out of the window again.

 

[Steffen Vala]

This is affecting both standalone monitors and capture card v/a monitoring equally.

Wouldn't the genlock be sync'ing the signal to the monitors too, through the hdsdi cables? What is happening to the signal in between the footage capture to the disk and the 720p preview output? Could it be something with a 30fps to 25 pull down on the preview output?

Also, it doesn't happen when camera is recording.

 

[ericyoung]

Your standalone HD-SDI monitors will lock to any source (genlock or not) as long as it's compatible with the HD-SDI standard the camera is putting out.

As you are in 50Hz, 25fps land, why are you recording 30fps - and there should be no need to do anything to do with pull down? Of course you can record any frame rate you like, just generally in 50Hz, 25fps countries, it's wise to stick to multiples of 25 such as 25, 50, 75, 100fps to avoid light flicker problems. Also, your camera project timebase should be 25fps for almost all types of shooting.

However, the fact it doesn't happen when recording is a clue - check your Playback settings!

On the camera, select:
System>Setup>Preferences>Playback>HD-SDI
If it's selected to 1080p that means the video out coming out of the two camera video out connectors labelled HD-SDI is at 720p when recording and 1080p when not. This switching will cause monitors and other equipment attached to either of those outputs to momentarily blank as they switch standards. Select this option to 720p, and all the camera video out connectors will always stay at 720p.

 

[Steffen Vala]

Thanks Eric,
Actually we are recording 25 fps base frame rate. I mentioned the 30 or 29.97 b/c I was thinking the camera might have some base/native framerate type thing in the video preview output pipeline, wherever it splits from the r3d record. I don't know if that makes sense, it was an idea that we thought might be possible.

The playback is set at 720p actually already. And we aren't doing any play back of clips off the camera... that's what the Qtake is here for

What else? Phase or signal issues from the genlock cable itself being wired near the rest of the moco cabling?

 

[ericyoung]

Well, also check:
System>Monitor>Preview is set to VIDEO[720p] and not MENUS [DVI]
and:
System>Monitor>PVW REFRESH is set to 50Hz and not 60Hz

Other thing is what are your settings on the genlock unit?

 

[Cail Young]

Hi guys,
We're on set here with a tri-level sync genlock feed from the moco dudes that seems to be causing an irregular/sporadic drop out on the video out feed. It doesn't seem to happen when genlock is disabled in camera.

Every time I've seen this happen it's bad cabling or a faulty genlock source.

 

[Steffen Vala]

These were already set as such:
System>Monitor>Preview is set to VIDEO[720p]
System>Monitor>PVW REFRESH is set to 50Hz

I'll have to see what the genlock source is doing and the cabling...afterall its not a showstopper by any means, but annoying for sure.

 

[Steffen Vala]

So I've learned they're using a AJA GEN10 and apparently the moco controls loses sync if the GEN10 is not set to 1080i. So there is a difference there between the 720p of the R1 and this sync signal.
Also the Qtake can't get a proper signal if it takes the REF In from the sync box.
I don't know much about issues with the sync box, but will look into it now.

 

[Steffen Vala]

A shot of the dip switches settings...

 

[Steffen Vala]

update: I had to change media to a RED Drive, due to filling up our two RAMs... and now there's no dropout. Coincidence? Maybe.

Edit: too fast on the trigger...dropouts back again

 

[Gunleik Groven]

I have had Genlock causing these issues, shooting at 25fps, too...

we had to kill it to get it done.