Show Relay video feed - how to get zero delay?

[james3mc]

So our very old analogue camera that feeds all of the very old analogue back-stage monitors is no longer fit for purpose. No problem, we can just buy a new camera, some new monitors and HDMI the lot.

 

The problem is that in all of our trials, sending the image down the HDMI route causes delay.

 

Even sending it down Cat5 instead only reduces the delay by a small amount.

 

So how can one get a reliable digital feed but without the delay, just as we used to with our trusty analogue camera and tired bit of coax/BNC?

[gyro_gearloose]

Many consumer CCTV cameras seem to be analogue. It might be worth trying one of those rather than keep your digital setup.

[Shez]

With digital, you'll always have latency. Analogue end to end is the only way you'll avoid it.

[timsabre]

This means using an old crt monitor... You can get beautiful quality broadcast crt monitors on ebay for not very much

[Joe Fernand]

How far do you need to send the signal?

 

Joe

[paulears]

Audio latency I can live with - and do, but video latency really annoys me. I've just finished a video project and in all the shots are big screens, and when syncing the multicam clips on the timeline, I'm amazed how far some of these lag behind - I am sitting there slipping tracks back and forth on a timeline trying to get things aligned within a single frame - and in this one, the drummer has been very handy - thanks to huge downbeats he's been doing - but I have no idea what happened with the venue video system - cascaded latency I suspect, and some were getting on for twenty frames - that's bad. In one of the edit points, the screen was VERY visible and the drummer on the screen actually took over, but it looked great - so I had to actually move that clip forward in time or it looked wrong.

 

Once you start using digital for video - you have to accept a poor result. The best you can get seems to be SDI, with the extra expense that equipment that uses it is more expensive. HDMI seems to be much worse - and the latency unpredictable. I don't think there is even a solution, just degrees of horribleness. I'm about to install the show relay for the summer, and I'm going to use some of my less often used HD cameras and monitors all wired in SD composite. The existing system with a consumer digital camera is going - just annoys me too much (as it looks like it will be me using it an awful lot this year). Last year, our SM grumbled, but I didn't do anything.

[Dave m]

If it is for foh or backstage then a bit of latency is not an issue but any operator or MD needs lag freeEasiest is any sound to be delivered via the video cable so at least the sound is in synch

 

Unless you have hd-SDI monitors, even using an hdmi converter from a HDSDI camera is a painSo composite and crt is better and cheaper

I used to do an event at the Brighton dome and my mixed video was sent backstage to a conversion box and eventually went to a big screenThe big screen was way behind the action

[lite_lad]

If you are going digital then you do need to spend a lot of money to reduce latency (you'll never get rid of it completely but can make it almost imperceptible) and go into things like genlock to ensure that signals pass through kit in the shortest amount of time possible.

 

For a simple system the best option is still analogue for show critical timings.

[Jivemaster]

Look for CCTV cameras with BNC connectors! It's an easy indicator of a simple analogue system. Even look for a spare! At the moment digital and latency are certainly coupled, probably the latency will shorten as systems make progress.

[paulears]

I don't really see how - the entire design philosophy of digital is complete frames, so you cannot read it out until it's been read in, so that takes a finite time. Blackmagic design seem pretty open about it, and the best seems to be 3 frames, with 5 as a likely end result with minimal processing. The video fraternity seem to find this the fastest in to out being quoted. Start to use domestic HDMI and it quickly creeps up to 10 frames delay or worse!

 

Like digital audio - while latency there is down to around 5mS or so, 11-15 is still common on some kit and worse on others. Nothing is actually live any longer - everything is delayed, but the question is how much.

 

I do video work, often on stage, and it's really horrible trying to frame something closeup, live using the big screens. Moving the camera and then having it happen later on the screen is very strange.

[david.elsbury]

Look for CCTV cameras with BNC connectors! It's an easy indicator of a simple analogue system.

 

Actually it really isn't sorry -SDI, HDTVI (or HDCVI) and HD-over-coax all use BNC connectors but aren't analog composite video...

[dbuckley]

Even look for a spare!

 

Lots of older analogue CCTV systems are still out there and being converted to IP; make friends with a local security company and they may be very happy to give you a few older monitors they've replaced and need to dump. I have half a dozen CRT monitors in the garage, and a couple of cameras.

 

Analogue cameras are still easy to get from Ali.

[gyro_gearloose]

No need to buy from Ali Express. There are plenty of places selling analogue cctv cameras, including Screwfix, Maplins, CPC, and plenty of other places. Even though almost all cctv servers these days seem to be capable of remote viewing via Ethernet/ the Internet, the cameras are still analogue.