Zero Latency Video of Conductor

SDI has the lowest latency of digital video but each device still has to process the video to some extent.
LCD TVs now have game mode which reduces processing and processing time and BlackMagic studio cameras have (I believe) the lowest latency.
Overall with something like a $500 vizio tv in game mode and a $1200 BM studio camera, you should have about 5 total frames of latency. At 60fps, that's fairly small.
Otherwise, analog.
 
The only way you can have "zero" latency (actually, a line or two), is to go all-analog NTSC.

If you go digital at *all*, you are at the encoding latency of the MPEG hardware encoder, and the *theoretical* minimum latency there is 1 frame or 2, depending on how you do the math; it is *impossible* to get "zero" latency if anything is digital.

There's a decent likliehood that *any* flat-panel display is going to introduce at least one additional frame of latency, as it has to digitize entire frames of incoming NTSC/analog, as well.
 
I’ve been searching for zero latency for ages knowing that zero latency is something impossible to achieve, but all the topics are a bit misleading and I started to believe there was a zero latency holy grail. But soon reality kicked in! I’m doing this show with 2 cameras live in a play, so latency is a big issue between live sound from the actors and the live feed from the cameras being projected. We are rehearsing at the moment and instead of anprojection we’re using a big screen tv to see what we shoot and the latency that the tv adds is mindblowingly huge! I haven’t tested the actual projector we’re going to use but i’m crossing my fingers that the latency doesn’t become a problem. We’re using SDI from cameras to a blackmagic atem tv studio, the output is also sdi!
 
Projectors will generally have a far higher latency than tvs. Even though they can have a "game" mode, which will always be the low latency mode, Sony and Epson projectors have about 25ms of latency, compared to your tvs which could be around 5ms.

Also consider the speed of sound, which is why even though "professional" products are typically better, like the ATEM with its 1ms of latency, large venues have delay built in by nature of how far away the viewer is from the screen. If someone is sitting 100 feet away, that might be 90ms of audio delay, so reducing delay caused by the digital video is a waste of time since their lips will never match anyway.

The conductor example is great because someone comparing large arm movements in person with the monitor behind them is super obvious.
 
Projectors will generally have a far higher latency than tvs. Even though they can have a "game" mode, which will always be the low latency mode, Sony and Epson projectors have about 25ms of latency, compared to your tvs which could be around 5ms.

Also consider the speed of sound, which is why even though "professional" products are typically better, like the ATEM with its 1ms of latency, large venues have delay built in by nature of how far away the viewer is from the screen. If someone is sitting 100 feet away, that might be 90ms of audio delay, so reducing delay caused by the digital video is a waste of time since their lips will never match anyway.

The conductor example is great because someone comparing large arm movements in person with the monitor behind them is super obvious.
The actors will be miced (is that how its spelled?! I’m thinking about mice now) so my main concern will be syncing the audio with video. But definitely latency is still an issue. Do you think that pro projectors with SDI IN will cause a lot of latency still?
 
Is there an SDI to HDMI conversion going on to drive the TV? That would add latency on top of the others in the system. Also, run the entire system at the TV or projector's native resolution and frame rate Any down conversion will add latency.
Now that we're rehearsing with Flat screen tv I'm running a good quality SDI to HDMI converter, but on the actual show It'll be SDI directly from my video switcher to the projector. The projector native resolution is 1920x1200 and I can only work on native video resolutions, so I'm working in 1080i signal. Don't know if there is a significant downconversion/latency issue with such a small difference in pixels. What do you guys think?
 
How does the latency feel now with the TV? I presume the reduced latency of the tv vs projector, plus the added latency of the sdi->HDMI would be about the same as the inherent latency of the projector.

1920x1200 is unfortunately not a native video resolution, its a native computer resolution.
Good news though, the projector doesn't scale 1920x1080 to 1920x1200, it just has 60 pixels of black on the top and bottom.

Did you say your switcher is a black magic ATEM? Or did I imagine that part?
 
How does the latency feel now with the TV? I presume the reduced latency of the tv vs projector, plus the added latency of the sdi->HDMI would be about the same as the inherent latency of the projector.

1920x1200 is unfortunately not a native video resolution, its a native computer resolution.
Good news though, the projector doesn't scale 1920x1080 to 1920x1200, it just has 60 pixels of black on the top and bottom.

Did you say your switcher is a black magic ATEM? Or did I imagine that part?
Yes it's a ATEM tv studio HD.
The latency in the TV is HUGE maybe because of this particular tv, but you're saying that the SDI ->HDMI conversion + the TV is about the same as the projetor is making me a liitle (panic) nervous:) I would assume that a SDI direct to the projetor would have less latency than the set up we're using for rehearsals.
Please say it ain't so!!!
Thanks
 
In the current setup you're describing, the TV is your largest source of latency (unless it's a commercial-grade display). TV's add delay doing 'Motion Smoothing' and gimmicks like that. Turn everything you can off to speed it up, or look for a "Gaming mode," which is marketing-speak to reduce delay.
Projectors usually try to do all the same image processing that the TV's are doing, plus keystoning, digital scaling/shifting, etc. It's good that the projector has SDI in- you'll do away with any conversions. Still, turn off as many features as you can- the less processing the image needs the faster the projector will be able to do it.
 
In the current setup you're describing, the TV is your largest source of latency (unless it's a commercial-grade display). TV's add delay doing 'Motion Smoothing' and gimmicks like that. Turn everything you can off to speed it up, or look for a "Gaming mode," which is marketing-speak to reduce delay.
Projectors usually try to do all the same image processing that the TV's are doing, plus keystoning, digital scaling/shifting, etc. It's good that the projector has SDI in- you'll do away with any conversions. Still, turn off as many features as you can- the less processing the image needs the faster the projector will be able to do it.
Alright! That sounds spot on! I turned that gaming mode on but didn't notice any significant improvement. Sounds like manufacturer bullshit! And for me "motion smoothing" is always off!
Thanks
 
Alright! That sounds spot on! I turned that gaming mode on but didn't notice any significant improvement. Sounds like manufacturer bullshit! And for me "motion smoothing" is always off!
Thanks
It's not bullshit... per say, but calling gaming mode a solution isn't really true. In my experience it makes a negligible difference, especially when it comes to conducting. It just doesn't help when the video is still a half beat behind.
 
There is a very low (~1ms) latency solution that we use here: https://www.teradek.com/collections/bolt-family

We have this in place for the clean range more than the latency, but it is a bonus with a real-time display for the public to watch.

If you went: HDSDI camera (like an inexpensive Marshall) direct to the Teradek Transmitter then Teradek RX direct to the display, you would have about the least delay possible in the transmission system aside from analog.

We don't have need of the 4K variant here and the street cost is a few thousand dollars. The RX has HDSDI and HDMI out on the same timetable.

I have used the 4K rig for monitoring of steadicam systems on set and it is pretty amazing...

Your mileage may vary.
 
I'm not sure how the teradek can somehow induce less latency than SDI over a cable.
Adding components to the signal chain like video switchers and converters will add negligibly more latency, but even a string of converters won't have as much latency as the tv or projector itself and I'm saying projectors inherently have more latency than TVs.
 
I agree. For reasons unknown, projectors are pretty awful. Barco's are not as vigorous with the internal processing, but are EXPENSIVE... :(
 
Hey sorry to interrupt! But how much money would cost to have 0 latency? What kind of equipment?

Well, if you dust the cobwebs off some old analog gear, free!

Ignoring the technicality that nothing has true "zero" latency, analog included, a digital system really depends on the weakest link, any one given piece of gear across many price ranges could buffer and / or incur a processing delay that induces more latency as already mentioned. Trial and error, and not commiting to anything expensive without testing it is pretty well.

In theory, a network NDI setup can have latency counted in lines when implemented correctly, but given how framebuffers work, they admit you're generally looking at one frame minimum, which mind you is only 16.7ms at 60 frames per second.

an SDI based setup (no converter boxes, everything outputting to / directly accepting SDI) would be likely to yield good results.

(Dumb question, assuming audio is mixed digitally, or you have a some form of outboard gear that can add delay, could you fudge the mix enough such that the monitors and house mix line up with what is being seen by the actors on screen?)
 
It is not a dumb question at all. Perfectly possible... but you end up with a slapback kind of delay to the ears of the performers that is difficult to talk against, much less sing against.

Until we get quantum computers that can violate the laws of physics... we are going to be late.

The trick is to minimize the lateness in the critical paths...
 
Well.... zero latency is going to be relative as mentioned above. However you can certainly come close to making it a negligible drift, but you need the budget that allows for it. A majority of my time is now spent Engineering for Film/TV and the integration of Live Performance to the Screen... but in order to get the least amount of lag, with the highest quality of picture and audio we have a team of 5 full time engineers, plus show crew, plus tv crew with a mountain of Video Servers, Fiber Optics, frame syncs, encoders and decoders. You might look into an NDI solution which is a sort of hybrid signal that lives between SDI and Fiber, but does work for 4k video....

It's all about the tools and the budget. You can get darn close enough. For me as long as I live at or below actor response time than it's a part of the production and it will likely work. Good Luck!
 

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