40m picture feed to projector

[richardash1981]

Another one of these questions!

Church service in the main church building, also live streamed:

• single camera + slides
• Fed into OBS on recent Apple Mac laptop computer
• 4G uplink to YouTube.

As a result of ongoing crowding concerns, we want to relay the picture and sound to projector / PA in the adjacent church hall (all one building, but through two doorways and down a corridor).Projector is probably native 1024x768 (although will be working cropped in widescreen as 1024 x 576?), say 4000 lumens and a biggish tripod screen, so not huge. We think we can do USB-C out of the computer to a USB-C to VGA/HDMI/audio hub device to get a second screen on the computer, and OBS will display the programme out full screen on the second monitor.

 

I paced it out and it's in the region of 40m of cable run from where the computer will be, to where the projector will need to be.This is a one-off, so it's roll out the cable night before job.

 

The basic option is 75 ohm coax and running composite video - this probably means USB-C out of the computer to a USB-C to VGA hub, then VGA to composite converter. At the projector end, signal goes straight in to the yellow phono socket.This isn't going to look great however, because it will have been both downscaled and frame rate converted (at least once).

 

My gut feeling is that 40m of VGA cable (which I might have a 30m and a 15m) isn't going to work reliably, and HDMI cable (which I don't have) certainly won't!

There are a multitude of HDMI over network cable devices around, can anyone offer any recommendations?Would I be correct to assume that all the cheaper ones are essentially proprietary (incompatible and somewhat unpredictable?) and there is a significant cost premium to something more standardised like HDbaseT?

Edited August 8, 2021 by richardash1981

[Stuart91]

We've found optical HDMI cables to be a relatively straightforward option for things like this. (Make sure you run them the correct way round).

 

40-odd metres of VGA can be done in a pinch but isn't a brilliant long-term solution. You could do VGA via CAT 5 but something at least notionally HD-compatible is more future proof and probably a wiser buy.

[dosxuk]

HDMI to HD-SDI converters are pretty cheap and will then happily do 40m on semi-decent coax. Only real constraint is video resolutions - you need to be using a broadcast resolution (rather than a computer one) - e.g. 1280x720 or 1920x1080 rather than 1024x768.

[TomHoward]

40m VGA would probably work but have some shadowing etc. In my experience at the budget end it tends to be more reliable than budget Cat5 solutions or HD-SDI with budget cable, in that those options give a better picture quality when they work, but VGA tends to work straight off. Will probably pick up a bit of static as well.

 

If the spaces are far enough apart that the delay isn't a problem, if you can't hear one venue from the other could you just display the Youtube stream?

[sunray]

40m VGA would probably work but have some shadowing etc. In my experience at the budget end it tends to be more reliable than budget Cat5 solutions or HD-SDI with budget cable, in that those options give a better picture quality when they work, but VGA tends to work straight off. Will probably pick up a bit of static as well.

 

If the spaces are far enough apart that the delay isn't a problem, if you can't hear one venue from the other could you just display the Youtube stream?

Wedid something similar for a bishops funeral, our run was 3 40m VGA cables but we had to add a VDA at each join else the sync failed. Obviously a bit soft but usable. We did try converting to CV but those days our converters were poor.

[Pete McCrea]

If the people in the relay hall have no visual reference to the main space, you could use a laptop on the remote projector and watch the live stream in the relay space. Obviously there will be the propagation delay through internet, so there will be a reasonable delay. If people can hear singing from the man in room the relay room in might not be workable.

 

Another option could be using NDI on a temporary wired network between the two spaces and using a second laptop to receive the NDI feed from the streaming laptop.

 

As a rental company, on a temporary basis I’d probably tackle it with hdmi out of the streaming laptop, HDMI to SDI conversion ( Decimator Design MD Cross v2 my preferred one as it will scale the HDMI to a chosen set resolution rather than take HDMI and simply spit it out on the SDI feed) then run a length of HD-SDI rated coax between the spaces and convert back to HDMI at receive end.

[richardash1981]

Thanks for all the advice.

Re: displaying YouTube - it's a possible option, but once all the doors are open for ventilation, I suspect we will have sound bleed through (the band will probably be fairly loud). We are also relying upon mobile data for the internet, so doing so doubles up the load on the cell tower, even using two different modems/SIMs.

 

VGA with a VGA distribution amplifier 15m down the cable (and mains extension to power it!) is probably an option. I've got a VGA DA with supposed EQ controls on two of the outputs, but they only boost the picture channel, makes no difference to the syncs! However I think it will at least square the sync pulses back up by putting them through a logic gate or equivalent.

 

I had assumed that an HD-SDI solution would be much more expensive, but I see that there are now no-brand converters available both ways quite cheaply. Having something which can be used with HDMI is attractive for other projects in the future, even if just to move the camcorder (HDMI out) away from the streaming laptop. The pair of converters seem to be the same sort of price as a fibre optic HDMI cable (I didn't know these were a thing!), but I worry about the risk of kinking it and writing the lot off (as opposed to coax, which can be replaced or chopped in two and re-terminated). Using a broadcast resolution wouldn't be an issue (I know the projector will take 720p input) and I'm sure OBS can oblige at the source end.

[dje]

A cheaper option (just in terms of what's available in more consumer brands) might (I say might - I don't know) be an HDMI-over-Ethernet system and then an Ethernet extender system.

 

It's a bit of a hotchpotch solution but it does work (done it myself) and with Chinese-made consumer/prosumer branded gear may be cheaper than commercial video equipment.

 

Of course, you do tend to get what you pay for but I also respect that for some people just don't have the upfront cash to spend what other people in this industry would consider "about right" so take this as being 'an option' but not necessarily the best one.

[timsabre]

I've used the cheap hdmi-sdi converters available for about £20 on Amazon and they've always worked fine for me.

 

We've also done the "show it on youtube" approach using mobile data both ways and that has worked fine too (once we got onto a network with decent signal) - you need about 5mb up and down to stream 720p

[Joe Fernand]

HDBT is great for point to point when you know you are unlikely to want to add additional Source or Display devices.

 

HD over LAN and UHD over LAN are more flexible when you need to start adding additional Source or Display devices - you simply add in a managed or unmanaged network Switch and add additional Transmitter and Receiver devices.

 

Both systems will easy pass over a 40M cable.

 

We supply all three options from Octava Inc. the HD over LAN system is very costs effective, https://octavainc.com/hdmi-over-ip-hdlan-poe/

 

Joe

[Stuart91]

I've used the cheap hdmi-sdi converters available for about £20 on Amazon and they've always worked fine for me.

 

We've had pretty bad experiences with the ones we've bought at a similar price. As well as some just plain not working, we've had the BNC connectors physically detach.

 

On the other hand some that we've put into installations have continued to work happily so it may just be that they don't like life on the road.

 

(And I've had similar problems with BlackMagic units costing an order of magnitude more)

[timsabre]

I've used the cheap hdmi-sdi converters available for about £20 on Amazon and they've always worked fine for me.

 

We've had pretty bad experiences with the ones we've bought at a similar price. As well as some just plain not working, we've had the BNC connectors physically detach.

 

On the other hand some that we've put into installations have continued to work happily so it may just be that they don't like life on the road.

 

(And I've had similar problems with BlackMagic units costing an order of magnitude more)

 

I have obviously been lucky...

[richardash1981]

The discussion here reminded me that I own a VGA-over-CAT5 kit, so today we did some testing, and in general things all worked well:- 15m VGA -> DA -> 30m VGA -> monitor / projector worked fine (except no DDC, so projector insisted on showing 16:9 content as 4:3, and the remote is lost), with a little ghosting visible.

- VGA over 50m of CAT6 cable (20m and 3 x 10m with couplers) also ran fine. This is a no-name kit I bought from CPC at some point.- I'm sure I've got a Kramer VGA over CATx kit, but I can't find where I have put it ...

 

I will be coming back to HDMI solutions however because a latter job in September involves a large HDMI screen on the front wall of the building, with the HDMI input port directly underneath it.