# Projector Connection for Auditorium Users- is there a better way?



## manuallyfocused (Nov 8, 2017)

I can't decide if this belongs in this forum or in "Facility Operations," apologies if I chose wrong.

We have a large Epson projector hung from the ceiling in our auditorium, projecting onto a motorized screen that rolls down in front of our stage. Connection is accomplished by HDMI via a balun, with a splitter so that users can connect both in the booth and from the front of the stage (the stage connection is also through a balun). This was set up by our IT department a couple of years ago, and drives me crazy when it doesn't work properly. I think I have the booth connection under control, though even that is occasionally unreliable, but it's the HDMI connection on the front of the stage that gives us fits. We are experiencing intermittent connection loss/flickering with a variety of cables and different types of computers, even when the computer is sitting still with noone touching it. IT has failed to come up with a good solution, so I'm trying to troubleshoot.

Is there a better standard than HDMI to use for connection that would still be easily compatible with most of our users? I'm loathe to go wireless, but I've been having good success with projecting from laptops to installed screens in other classrooms, and wondering if that might work better. I wish I could convince everyone to just use the installed computer in the booth, but they seem intent on using laptops from the stage.

Thanks for any suggestions!


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## kenact (Nov 8, 2017)

Without knowing the structure of your environment, one possibility would be to run an actual HDMI from the projector to the booth, and a male/female HDMI from the booth to the stage. When you need to run from the stage, connect the 2 HDMI cables in the booth.

Another possibility, if your projector has multiple interfaces, use HDMI for the booth, and VGA or RGB for the stage. If you only have HDMI on the laptop being used at the stage, no problem. There are VGA to HDMI and RGB to HDMI adaptors.

If you're trying to use both at the same time, all bets are off.


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## microstar (Nov 8, 2017)

manuallyfocused said:


> I can't decide if this belongs in this forum or in "Facility Operations," apologies if I chose wrong.
> 
> We have a large Epson projector hung from the ceiling in our auditorium, projecting onto a motorized screen that rolls down in front of our stage. Connection is accomplished by HDMI via a balun, with a splitter so that users can connect both in the booth and from the front of the stage (the stage connection is also through a balun). This was set up by our IT department a couple of years ago, and drives me crazy when it doesn't work properly. I think I have the booth connection under control, though even that is occasionally unreliable, but it's the HDMI connection on the front of the stage that gives us fits. We are experiencing intermittent connection loss/flickering with a variety of cables and different types of computers, even when the computer is sitting still with noone touching it. IT has failed to come up with a good solution, so I'm trying to troubleshoot.
> 
> ...



Not sure how you are using the word "splitter". I think of splitter as taking one input and going to two or more outputs. The way you describe the system, you would need a "combiner".... taking two inputs from laptops and merging them into one output to the input of the projector.
If the projector had two HDMI inputs, then each laptop could go to a separate input and you would switch to the proper input with the projector remote control. Or maybe I don't understand how it works at all.


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## Senorfish (Nov 8, 2017)

Sounds like your problem is the HDMI runs are too long? HDMI signal is only stable for about 25', some sources claim up to 50', but why push your luck when the audience is giving you the "when is this lecture going to start" 100 yard stare? For HDMI runs beyond 25' you need to convert to a longer range wire and format. How's it's done is your HDMI source--> Blackmagic convertor box (usually converts to a cat6 type connection or SDI connection)--> that cat6 or SDI cable covers the up to 300' long distance--> then Blackmagic box #2 at the tech booth or projector end to convert cat6 back to HDMI--> HDMI input at projector. There are numerous variations of these little signal convertor/booster boxes, but in essence this is how it goes long distance without dropouts. Something like this https://www.bhphotovideo.com/c/product/1073318-REG/smart_avi_hdx_lxs_hdx_lx_hdmi_and_ir.html

or this
https://www.bhphotovideo.com/c/prod...ic_Design_CONVMBSH_Mini_Converter_SDI_to.html


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## Amiers (Nov 8, 2017)

Would be helpful if you told us the type of balun you have as well as if the cable is cat5 6. 

Maybe some pictures too.


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## josh88 (Nov 8, 2017)

Senorfish said:


> Sounds like your problem is the HDMI runs are too long? HDMI signal is only stable for about 25', some sources claim up to 50'



While I agree completely, especially with the why risk it statements, we have 75' and 100' hdmi cables in our inventory and regularly use them without issue. That being said over 50' we're usually using a splitter of some kind which boosts the signal. Its one of those "it works till it doesn't" kind of things. My first thought too was that it sounded like the OP has too long of a run and thats why signal is dropping out and in my experience that would explain it all. 

My ideal would be getting a convertor (the black magic boxes mentioned above, or we use a product made by AJA) and converting to SDI for the long run and either getting a projector that takes SDI or converting it back to HDMI at the other end of the run. We do this all the time for runs between 50' and 200'


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## ruinexplorer (Nov 9, 2017)

Sounds to me to be a bandwidth problem if you are having intermittent issues. I agree that it will be helpful to know the type of balun, the category cable, and the type of switch (not splitter) that you are using. 

I prefer DVI to HDMI. They both use TMDS protocol, but DVI doesn't have audio (unneeded in most cases), it doesn't require HDCP, and it locks in place. If they only have HDMI port, then a simple passive adapter is all you need.


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## manuallyfocused (Nov 9, 2017)

The balun is an Atlona AT-HD4-SI40SR. The splitter/audio extractor is a J-Tech Digital unit: http://www.jtechdigital.com/j-tech-...l-spdif-rca-l-r-audio-out-remote-control.html

IT has now replaced the plug itself and the connection appears more physically stable (I can jiggle around the cable at both ends and this doesn't seem to affect the data connection) but we still get intermittent signal loss.


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## Amiers (Nov 9, 2017)

So it looks like you got something in the cheap side. Reading the top review. 



So... time to bust out the measuring tape. Or upgrade your balun to reflect the distance of the cable traveled. 

Best way to test your balun is to get multiple lengths of Cat5/6/7 cables whatever you use and start some trials with a laptop and monitor. This will tell you roughly how well they work. Rated 130 but rated never means what it really means in this particular situation. 

A side note this always pops into my head when talking about laptops and connections.


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## teqniqal (Nov 9, 2017)

There is still no mention of the cable used. Shielded CAT6A will perform better at longer distances than lower category cables, so this may provide the necessary bandwidth for a more stable operation. Cable quality matters. The Belden 'bonded-pair' data cable is better at rejecting internal data pair cross-talk and external interference than most other cable structures.

You also did not let us know how long the cable run is. Distance matters. Cable capacitance is greater in longer cables, so this shunts-off the high frequency response and the signal can fail.

Data tranmsmission rate matters. Is there any chance you are using a different refresh rate for the line that fails? 1080p/60 requires twice the bandwidth that 1080i or 1080p/24 (film reproduction) does.

The quality of the RJ45 connector and the workmanship of the crimp can affect the functional bandwidth. A CAT5 connector crimped onto a CAT6A cable will only reliably provide CAT5 throughput. Using the IT department's CAT6A cable tester to verify that the cable assembly between the signal converters is fully capable of the data bandwidth is a good idea.

Alternatives NOT suggested but worthy of consideration:

Replace the 'balun' encoder / decoder and cable with a Fiber Optic HDMI link. (easiest to install, but a bit fragile if you have ham-fisted users)

Replace the 'balun' encoder / decoder with a HDBaseT transmit / receive pair.
Replace the 'balun' encoder / decoder with a IPBaseT transmit / receive pair.

Replace the 'balun' encoder / decoder with a HDMI to IP (typically H.264, but there are many other [sometimes proprietary] protocols, too) transmit / receive pair (this is a great option as you can stream the program to other computers throughout the school).
If you chose to replace the 'balun' encoder / decoder and/or cable, purchase equipment that supports 4K UHD 4:4:4 transmission so as to 'future proof' the cabling for when the projector gets updated to 4K UHD (it could happen - prices keep falling). Of course, if you are going to present any content that is protected (DVD, BlueRay, TV Broadcast, etc.), then you need to use a system that explicitly is rated to be HDCP compliant.

And those short cables that connect the 'balun' to the endpoints -- those should be good quality, too. Cheapo HDMI cables can botch the whole process in nothing flat.


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## gordonmcleod (Nov 15, 2017)

I have used these many times and have found they did what they claimed reliably

https://www.monoprice.com/product?c_id=101&cp_id=10914&cs_id=1091401&p_id=15778&seq=1&format=2


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## avkid6345 (Nov 16, 2017)

Does the balun have one Cat5 or two? We didn't have much luck with the ones with 2 cables. We would have dropouts and random connection issues. We switched over to HDbaseT extenders and that solved all of our issues.


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