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Discussion Starter · #1 ·
Question:

Could a direct video signal feedback loop fry video equipment?


I am working on a video system design with IMAG capability where it is possible to configure the screen switcher & camera switcher to create a video feedback loop.

See attached PDF for a full system schematic.


With this proposal, there are actually 2 possible feedback loops (if configured wrongly):

1.) VP-730 output -> VP-701xl input / VP-701xl loop output -> VP-8x8 input / VP-8x8 output -> VP-730 input.

2.) VP-730 output -> VP-701xl input / VP-701xl Y/C output -> Vaddio ProductionView FX input / Vaddio ProductionView FX output -> VP-730 input.


So, could such a configuration damage any of the video equipment?

 

Video System Plan VGA.pdf 82.0732421875k . file
 

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Since video is all line-level, you don't have to worry much about equipment damage from feedback loops, any more than with line-level audio. Likewise, pointing a videocamera at a screen isn't going to give you a huge damaging signal buildup. The big symptom of a closed-loop video path is no signal at the output.


I am, however, rather concerned by your block diagramme. It seems to me that there is a very good chance you're making your system more complicated than it needs to be. Feeding what is marked as a camera controller, for example, with only one input, namely the output of a scan-convertor downscaling the output of the production switcher, strikes me as difficult to justify. I really hope you had a qualified video professional look over this layout in order to check its validity.
 

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Discussion Starter · #3 ·
Thanks for the feedback regarding the feedback loop question (pardon the pun! ;-)


Regarding your other concerns:

There are 3 PTZ cameras input to the camera controller/mixer that are not shown on the block schematic.

The Vaddio ProductionView FX Camera controller & mixer can control & mix up to 6 PTZ cameras. Initially, there will only be 3 cameras connected to it. That plus the feed from the video screen leaves 2 inputs available for future expansion (like 2 more PTZ cameras).

The entire camera system (SD controller/mixer & 3 PTZ cameras) are already installed and the rest of the system is new. If everything were new, we would probably go with an HD camera system so conversions to SD would not be needed.


Despite the appearance, I am actually designing the system to be simple and easy to use (even though design and installation might be kind of complex). This system is to be used in a church.

The VP-730 switcher/scaler is used to control what is displayed on the two primary video screens (same signal on each).

The Vaddio camera controller/mixer is used to record video and distribute video to other screens around the church facility.

The VP-8x8 is mostly just a set and forget VGA hub that rarely needs any attention.
 

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It makes me feel much better to know that there are actually cameras attached to the camera controller.


I'm not sure how trouble-free your operation is going to be with three PCs in the setup I have found that computer video issues often tend to complicate things, over & above the usual computer complications such as virus protection, operating system updates, &c. I'm also not clear on the purpose of having a "confidence projector" which is not fed from the production switcher ; I would have thought that one of the two "presentation monitors" sufficed for that. Of course, I don't know the details of your application. I'm not the sort of person to be comfortable in the sort of church that requires this sort of setup!
 

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Discussion Starter · #5 ·
The confidence projector is for a projection screen on the back wall of the sanctuary so that people on stage (like the pastor) can see the screen without turning around.

The VP-8x8 switcher allows this confidence projector to also act as a teleprompter for the persons on stage. A different signal can be routed to the confidence projector than what is on the main screens. But most of the time, the confidence projector will just be fed the same signal as the two main projection screens.


The other two projectors are for the mains for the congregation. The screens are up front above the stage.


All the rest of the monitors are located in the control booth for the operators' benefit.


Hope that helps make sense out of this crazy design.

Yes, I agree it is kind of crazy, but it gives me everything I want in a pretty reasonable, easy to use package. (I think)
 
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