Video Engineers help needed

MikeWilkinson

MikeWilkinson

Veteran
Wasn't really a better place to post this on these boards....

I run the video production operations at my college, which includes live, 4-5 camera
video shoots in the auditorium. We have house patch boxes in the camera positions, with them returning to a spot in the both where I hook into my switcher.

This works OK, but I get some noticable horizontal banding on my video feeds.

Do I need to invest in some kind of Black Burst generator, or TBC or something to clean up this signal? I'm not an engineer by any means, so I'm not really sure if hardware like this is the answer, or if the auditorium's cabling is just going south or what... direct lines from camera to the switcher are OK, but distance is too far to do that all the time.

In other multicam environments I've worked in they had things like TBCs, even though time syncing isn't really an issue here, I don't know what I'm missing/doing wrong.

thanks...

Equipment I'm using:
4xDVCPRO cams
DataVideo switcher 800DV
DVCPRO Deck
 
sounds like you need a TBC. What happens if you only connect 1 feed (no other inputs at all) from a camera into the switcher? Do you still have the problem? If so it's not a TBC fix
 
Can't say. We don't run a switcher for single camera shoots, we record to tape. But's it's something I could look into.
 
Without out seeing the degraded signal it's difficult to determine the nature of the problem. It could be 60 cycle interference from a power line that runs paralell to your video cables. I'm guessing you're feeding the switcher composite video from the cameras. You could try a hum bucker but it won't eliminate all the noise.

The first step is to isolate the source of the interference. Is the noise on the output of the switcher or is it coming from the cameras? One way to check is to use a small portable monitor. Unplug camera 1 from the swithcher and plug it into the portable monitor. If the noise is still there the problem is being induced on the cable runs. Trace the cable runs and make sure that there are no power lines running paralell to them.

You shouldn't need a black burst generator or a TBC. I think that the DataVideo 800DV has a built in TBC and it doesn't require genlock.
 
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thanks milky, I'll check into it. We did implement grounding adapters a few months ago, and that helped a little.
When running test similar to the one you describe (isolating the problem) I never seem to have as many problems as when running a show. Maybe it's the fact that the audio/lighting system have been engaged at that point and all the power running around is too much?

If it is the case that power lines are causing interference, is there any remedy short of re-wiring the auditorium?
 
If there wasn't a solid engineering plan when the initial install was done you could be in for some work to resolve the problems. Well thought out facilities have seperated cable trays for AV and power to eliminate these types of problems. I've seen some ugly operations where cable was piled on over the years until it resembled a technicolor anaconda - not pretty.

Check out the cable runs inside the booth, it might be as simple as moving some of the video cabling around in the booth if it's too close to the dimmer. It's also possible that camera's AC power source and the power in the booth have different ground points which could cause a ground loop. I suppose you could run a test with a camera on battery power to try to see if there's a problem with the ground. Sorry to only bring up more potential problems rather than solutions, but you can't solve the problem until you know where the source of the trouble is. Hum bars can be a bear to track down in aging facilities.
 
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