Cheap video cameras and SDI - problems

[ABB125]

We have some really cheap, rubbish Praktika video cameras ("camcorder"). These are used, in conjunction with an assortment of Blackmagic SDI microconverters and PC monitors to set up video feeds when we run musicals with a pit band hidden away from the stage: one feed of the conductor being sent to all the locations they need to be seen in (typically 4 separate places), and one feed of the stage being sent to the conductor (so they can see what's going on).

Every single time this setup is used, there are problems and it takes many, many hours of frustration and trying the same thing in different ways to cobble together something which just about works. Usually, there are different problems each time, which adds to the "fun". Sometimes we test the system with a Sony NX5 just to make sure that the individual components do actually work, but for various reasons we can't use an NX5 for the actual shows.

Generally, the biggest problem is getting the cameras to work with the HDMI to SDI microconverters. The cameras have a mini HDMI output; we use either an adapter cable straight into the converter, or an adapter then standard HDMI cable. It has recently been suggested that one problem might be the resistance of the HDMI cables - is this likely, and if so what would the "correct" resistance be and how would I be able to check this on existing cables/before buying new ones?

Another problem is that some of the equipment doesn't always work in a specific way, but there's no way of knowing so you spend hours wasting more time. For example, at least one of our stock of PC monitors simply refuses to work with SDI microconverters, but is totally happy if you plug in an HDMI from a laptop. Or, the HDMI inputs on the monitors don't work, so you have to use DVI instead. (Yes I do try to label these things when I find them, but it's not always me who sets it up.)

Based on what I've said (I'm happy to clarify things if needed) are there any other obvious issues with this setup? Anything which a more experienced person would see and go "well of course it's not working properly, because..."? Any better ways of doing it (bearing in mind that the overriding priority is minimal latency; video quality is almost (but not quite) irrelevant?

If money was no object, what would be the industry standard way of doing this?

[Dave m]

To be honest, the way to go for zero latency is composite.

Digital is great, but every converter introduces latency. The cheaper you go, the greater the delay (normally) 

a camera with SDI is probably easier to distribute than hdmi.

[J Pearce]

HDMI encompasses a few standards. SDI is far more specific. Your HDMI computer monitors will be expecting RGB colourspace, in a variety of resolutions/frame rates. Your SDI adapters will send only video standards down SDI, then only video HDMI standards out of the HDMI - so 720p/1080i/1080p in YUV colourspace. TVs will display these standards, many computer monitors will not.

Unless you've got the cash for something like a Marshall SDI camera, I'd stick with composite. Most big musicals are still on composite for MD cameras (though there is now a growing move to SDI for FOH picture). Get a good quality composite camera (I recommend the Bosch cameras which can be found quite affordably on eBay), a composite video splitter (or distribution amplifier to use the proper term - again, plenty on eBay), use your existing BNC cabling, and either use cheap TVs (could be higher latency) or SD native screens - varying sizes available in varying ruggedness at varying price points.

Edited April 6 by J Pearce

[Stuart91]

Funnily enough, I was asked yesterday about something similar. 

We've got a choir on stage, with a conductor standing on a small riser on the auditorium floor. The band surround the conductor on the floor, choir and soloists are on the stage which is approx 4ft high. 

The problem is that the choir can't all see the conductor, only the first few rows. One potential solution is to add risers for the choir, but that'll involve quite a lot of hardware and expense for a show that's already tight for budget. 

Raising the conductor might help, too, but much higher and they'll block sightlines for the audience. 

Some video relay seems like the obvious option, but they've experimented with modern digital kit without success - there's just too much latency. 

I've been asked about possibilities. I know composite / analog is the way to go. I'm not sure though if, for example, running a composite signal into a modern flatscreen TV will still be latency-free, or if there's inherent processing / upscaling involved. The choir are large enough that we'd need some decent sized screens and alas my 32" CRTs went into a skip some years ago...

[J Pearce]

Most flatscreen TVs have a tolerable latency on their composite input. Some have a 'gaming' mode which improves this. I generally find that the more modern the TV the more likely it is to have fancier upscaling processing that increases latency.
For opera I'd be looking at CRT or low latency native SD resolution screens, but if you're after count ins, ends of pauses, and dynamics etc. then most flat screen TVs should be ok.

Most digital cameras are not remotely optimised for low latency live output, until you're into proper studio cameras. Add in digital processing and the frame delays get far too long for conductor cameras.

[ABB125]

Thanks everyone so far - analogue isn't something I'd previously considered as everything we do currently is digital(ish)!

Is this the sort of camera you mean @J Pearce? I think we have something that looks similar bodged onto what looks like it might have once been a mic stand, I'll have to investigate. We (and an associated organisation) have a random collection of various analogue video things, when I have time I'll have a proper look through to see if any of it might be useful (assuming of course that it works!). 

In terms of a composite splitter, are the really cheap plastic-y things like this "good enough", or does more money need to be spent for something of a better quality?

Is composite to VGA workable, so that the existing PC monitors can still be used? Various adapters appear to be available, should something like this work or would it have to be a powered device like this? I'll also have a look at the assortment of random screens* we have to see if there are any with composite input.

 

*ranging from what look like small black and white CRTs to 15 year old "commercial-style" big screens which came out of a library I believe...

[Stuart91]

16 minutes ago, J Pearce said:

but if you're after count ins, ends of pauses, and dynamics etc. then most flat screen TVs should be ok.

My lot have specifically said they struggled with count-ins, it's the down-beat at the start of a piece that is the biggest challenge. (Slow pieces seem to need more precision than faster ones, interestingly)

[J Pearce]

8 hours ago, ABB125 said:

Thanks everyone so far - analogue isn't something I'd previously considered as everything we do currently is digital(ish)!

Is this the sort of camera you mean @J Pearce? I think we have something that looks similar bodged onto what looks like it might have once been a mic stand, I'll have to investigate. We (and an associated organisation) have a random collection of various analogue video things, when I have time I'll have a proper look through to see if any of it might be useful (assuming of course that it works!). 

In terms of a composite splitter, are the really cheap plastic-y things like this "good enough", or does more money need to be spent for something of a better quality?

Is composite to VGA workable, so that the existing PC monitors can still be used? Various adapters appear to be available, should something like this work or would it have to be a powered device like this? I'll also have a look at the assortment of random screens* we have to see if there are any with composite input.

 

*ranging from what look like small black and white CRTs to 15 year old "commercial-style" big screens which came out of a library I believe...

Yep you've pretty much picked the setup that has just run a rather large musical at the Rep. Those DAs work fine, and the Bosch Dinion cameras are excellent, and very affordable on the used market.

I've not tried composite to VGA, I guess it'd depend on the signal delay of the specific converter. Some screens may support a passive cable adapter, it'd depend on their supported scan rates. I'd recommend avoiding converters and sticking to screens with native composite video input (or SCART with an adapter). Small black and white CRTs are ideal and probably go with the camera on a mic stand.

As you're local to me and my venue if you wanted to pop over and take a look send me a DM.

[J Pearce]

7 hours ago, Stuart91 said:

My lot have specifically said they struggled with count-ins, it's the down-beat at the start of a piece that is the biggest challenge. (Slow pieces seem to need more precision than faster ones, interestingly)

I'd be suspicious of the digital camera and distribution before the flatscreens. All of our MD camera setup is on flatscreens, and I haven't had any complaints about latency.

At my previous job the opera MD insisted on CRT and for what they were doing the very small latency from a flatscreen was perhaps an issue.

[sunray]

I have regularly put show relay in for village hall type shows, mostly to dressing rooms where latency is irrelevant, initially using 21" CRT TVs and composite, often running over cat5 with baluns. One venue had 19" flat monitors and VGA over cat5 receivers in place so sourced the same system from CPC and converted to VGA. despite being smaller the actors seemed to prefer the flat screens and found myself running VGA on 19" flat screens more than CV on bulky CRTs.

 

However a trip to the local tip at TV Digital switchover quite by chance I parked beside a vehicle from which a 15" and 19" analogue TV were being removed, the jobsworth staff member tried to argue I wasn't allowed to take them despite not even touching the ground, literally a direct vehicle to vehicle transfer and during that another person offered the 19" he was about to dump. Those 3 plus another 19" aquired since are my usual stock for such, occassionally 32"s/40"s from home when required but rare.

Do I regret disposing of CRT stock? Only once as relay to MD from SM feed. At one point both could be seen wiyh significant latency to MD.

I did try using a CCTV cat5 system... Yeah right, never again.

As far as I'm concerned it's analogue all the way, I just wish I could find a camera to cope with the dramatic light changes better.

[J Pearce]

10 hours ago, sunray said:

I just wish I could find a camera to cope with the dramatic light changes better.

As above, the Bosch Dinion kit is good at this. You'll need to spend money on a camera with exposure and shutter settings, any of the cheap auto exposure CCTV cameras will struggle with the dynamic range of a stage lit production.

[sunray]

1 hour ago, J Pearce said:

As above, the Bosch Dinion kit is good at this. You'll need to spend money on a camera with exposure and shutter settings, any of the cheap auto exposure CCTV cameras will struggle with the dynamic range of a stage lit production.

I started looking after I'd posted yesterday, I see a selection of models, are there any better/worse than others?

The usual camera I've been using for a long while was a pretty good CCTV camera 20 years ago, I think about 350TVL and TBH most of what its used for the momentary white/black out doesn't really matter that much unless there is significant flashing. As I'm claiming to have retired I'm not looking to invest much😉

[J Pearce]

I've not really paid much attention to model numbers, just whether it has the features I need.

[paulears]

For me, HDMI and HDMI converted to SDI is always a punt. Even worse, so many computer monitors are locked to very precise frame rates, and TV's that have HDMI inputs are much better at producing a picture. You grab a camera, it says 1980x1080 and you discover it has SDI out, so grab the blackmagic converter and stuff a short (because they're more reliable than long)HDMI cable in to the monitor, and get a framerate mismatch message, or worse, nothing. You plug a camera with HDMI out into a monitor with HDMI and it doesn't work - maybe 1080i not p, or maybe the length of the HDMI is just a tad too long? I've never found the answer, but it's infuriating.