# Video transmission for IMAG on a budget



## cpf (Feb 11, 2011)

So, working on doing the technical details for an upcoming small-scale conference (think around 300 people), and I was looking at doing one-man image magnification for exactly 2 events. Now, both of these events already have projection going into them, I have access to a TriCaster 100 Educational (woo), and an assortment of cameras (all with component video out, best one is a GL2), the only thing I've yet to determine is how to get the video from the cameras (thinking 2) all the way from the back of an auditorium, and the side of the stage, to the TriCaster box.

*So, here's my question:* What's a dirt cheap way of transmitting composite video up to 100' (I think, haven't checked with the staging people) with a signal that would still look decent on a 8x8(ish) projection screen, using a boardroom-style projector? I have soldering skills, the time to order stuff online, and under $100 to spend (it's a personal project that I haven't been able to pitch it to the money people).

Would a passive balun running the composite over CAT5/e/6 give me adequate quality? I have a pair of Radio Trash #15-2572 (manual) AV transmitters, but I'm not too trusting of RS's legendary product reliability, so that's why I'm looking for a hard-wired solution. Does anyone have any specific product suggestions?

So far I've looked around and found things like Video + Stereo Audio Hi-Fi Transceiver #500039 and One Pair Passive Composite Video Balun UTP AV to Cat5 on eBay.ca (item 350436433390 end time 03-Mar-11 15:29:26 EST) and all the advertised ranges are well over my need, but my Macbook's battery is also supposed to last like 8 hours.


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## Footer (Feb 11, 2011)

Why not just a standard coax BNC cable? Hosa BNC 59 1100 Video Cable, BNC to BNC, RG-59 Coax, 100 Feet | Full Compass

The GL2 is more then capable of pushing a signal 100' or more. Get a few BNC to RCA adapters and you should be set.


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## ruinexplorer (Feb 11, 2011)

For only around 100', you should just use RG-6 coaxial cable. No need to use a balun on that short of a run. Try here or maybe you have somewhere local that can provide it for you.


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## museav (Feb 12, 2011)

I agree with the coax but for i-mag I have to wonder about the latency involved with a composite video signal out of the camera, through the Tricaster and into the projector as there would seem to be quite a bit of A/D conversion, D/A conversion and scaling involved. That is not going to depend on the 100' cable run so if you have the cameras, Tricaster and projector available it might be worth mocking it up just to verify whether any delay introduced in the signal path is acceptable.


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## SHARYNF (Feb 15, 2011)

museav said:


> I agree with the coax but for i-mag I have to wonder about the latency involved with a composite video signal out of the camera, through the Tricaster and into the projector as there would seem to be quite a bit of A/D conversion, D/A conversion and scaling involved. That is not going to depend on the 100' cable run so if you have the cameras, Tricaster and projector available it might be worth mocking it up just to verify whether any delay introduced in the signal path is acceptable.


 
In my experience, you will have a frame delay in the camera, 3 frames delay in the tricaster, one frame delay in the projector for a total of 5 frames and the delay will be noticable if you look carefully and listen to the audio
Sharyn


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## museav (Feb 15, 2011)

SHARYNF said:


> In my experience, you will have a frame delay in the camera, 3 frames delay in the tricaster, one frame delay in the projector for a total of 5 frames and the delay will be noticable if you look carefully and listen to the audio


Just to provide some reference, at 30fps those 5 frames represent 167ms. With the speed of sound being 1130ft/sec that 167ms is equivalent to sound traveling 188'. So if the screen and speakers are in approximately the same location, then roughly 188' away the audio and video would be in sync. Beyond that the audio will start to lag relative to the video, closer than that and the video will lag relative to the audio.

One option if the audience is closer than that 188' is to delay the audio to match the video. The problem with this is that this can cause a noticeable disconnect with the natural visual and aural sources, e.g. hearing the natural sound and then the delayed sound as an echo.

In a large space you may be able to balance the two for much of the audience, but in smaller spaces it can be difficult to not have some noticeable lag between the direct visual image and the i-mag image or between the audio and the i-mag image.


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## Kingcaffeine (Mar 1, 2011)

I'm with Footer. The GL2 is very capable. No baluns necessary. Just get some good quality cable (Canare LV-61s, or RG-6) and you're done.


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