With multiple buildings and three different worship spaces, St. Mina’s Coptic Orthodox Church (see photo above) of Holmdel, NJ relies on the NDI video networking capability found in Panasonic’s AV-HLC100 Stream Studio and AW-HN38 Full HD pan/tilt/zoom cameras
"We don’t use SDI anymore!" and "SDI is dying..." Those are two comments in a recent discussion about NDI in a church tech group on Facebook. So, what does he use? NDI.
As techies, it's easy to want to jump aboard new tech and leave old options in the dust, but in doing so, there's usually a cost, whether it's an opportunity cost, a cost of ability, or a financial one. So, let's look at NDI and see if it's a panacea filled with unlimited possibilities, or has some downsides to consider as well.
SDI either gets there or it doesn't. NDI might get there, but be delayed.
First, let's talk about what NDI is. NDI is short for Network Digital Interface. It was developed by Newtek, creators of the Tricaster video switcher. NDI enables you to send one or more video streams over a network and it does so with low-latency.
While it is an encoded stream, it’s not designed for live streaming directly to an online audience, though. It's really meant to be a way to send video between computers or even from one video source to a switcher or computer within the local network.
If you have a single network that's already doing a lot of things, adding NDI might be too much for it.
While NDI was designed to have latency of less than a frame (and as quick as 8 scan lines with hardware implementations), in practice it might be a field to a frame of latency (https://support.newtek.com/hc/en-us/articles/218109667-NDI-Encoding-Decoding), but that's assuming the network is up to the challenge and isn't in use for other tasks.
While NewTek developed it and continues to evolve it, they also make the technology available to other vendors, and it is showing up in more and more products from a growing number of manufacturers.
While NDI is a low-latency way to send video throughout the network, and send multiple streams at the same time, that's also its limitation.
For example, PTZOptics sells PTZ cameras that can send video via NDI. Panasonic sells a video switcher which can use NDI sources alongside more traditional sources. ProPresenter 7, Renewed Vision's latest version of their popular worship software can send distinctly formatted outputs out over the network using NDI. Software encoders software like OBS (with a downloadable plug-in) can receive it as a source. Finally, Magewell even has small boxes that can connect to TVs to convert NDI received over the network back to HDMI for display.
NDI is not designed for live streaming directly to an online audience. It's really meant to be a way to send video between computers or from one video source to a switcher.
It's truly amazing all that NDI can do.
It's not perfect, though. While it is a low-latency way to send video throughout the network, and send multiple streams at the same time, that's also its limitation.
It may sound like the solution to video distribution problems that churches face, but its stability is dependent on those networks. If your network infrastructure is pieced together with donated gear that businesses have long-since grown past, you might not be able to send even a single NDI stream, let alone multiple.
If you have a single network that's already doing a lot of things, NDI might be too much for it, too.
If you think, "We've got good wifi, this is great news," think again.
With SDI, you've got a single cable running from point a to point b. On that cable, you can send a 1080p signal with no worries about congestion; it's dedicated to that purpose and it alone.
With NDI, if you've got a dedicated hardwired network, you can have even better results, sending multiple video signals on a single gigabit network...but if someone tries to do something network-intensive and turns the dedicated network into just another general-purpose network, you could have trouble, and have it intermittently.
Another problem is latency. If you're sending slides from a computer to your live stream, a few frames (which would be more than an NDI signal normally has) are no big deal. So, you have a little more flexibility with a live-stream.
While NDI was designed to have latency of less than a frame (and as quick as 8 scan lines with hardware implementations), in practice it might be a field to a frame of latency (https://support.newtek.com/hc/en-us/articles/218109667-NDI-Encoding-Decoding), but that's assuming the network is up to the challenge and isn't in use for other tasks.
If it isn't robust enough or someone else is using it for high-bandwidth applications, it's possible that your NDI could be delayed much more. It might seem that everything is working right, but you notice that the video doesn't arrive at its destination as quickly as you'd need for IMAG (which is usually under 3 frames total).
Case in point. In the same discussion group that one user (above) reported that he only uses NDI because "SDI is dying," another reported, later that same day, that he was having latency of about three seconds (not frames, mind you, but seconds). Everything looked right, except something was going wrong with what was an otherwise good network.
The pesky thing about this situation is that while SDI either gets there or it doesn't, NDI might get there, but be delayed enough to cause issues with audio sync or just enough to make lyrics that left on time seem late when they arrive.
Of course, this isn't the normal way things are, unless you have a bad network, but it is a real possibility if you don't have a good, dedicated one.
Putting in a dedicated network might be as simple as connecting two computers, but it might also be much more complex requiring you (or your IT person) to run new Cat6 and replace other gear with new.
If that's your situation, maybe running a single RG-6 to your lobby and buying a couple of BlackMagic Design SDI-HDMI adapters makes a lot more sense.
The price of the infrastructure to run a reliable NDI signal can vary wildly based on what you need. Sure, a brand new, dedicated gigabit network might enable multiple NDI video streams, but if you just want the nursery to be able to watch the service, perhaps SDI just makes more sense.
So, is "SDI dying"? Not yet. In portable situations, for example, properly coiling RG-6 and having it last for years, isn't gonna be an issue. Cat6 is a little harder to deal with and one bad conductor could make an otherwise good cable useless.
In situations where you need a single run for a single video signal, but where no dedicated network exists, SDI still makes a lot of sense, as well.
But, if you've got the infrastructure already, or a dedicated network only means connecting a couple of pieces of gear over a short distance, NDI sure is nice, especially for multiple streams.
So, is it a godsend? Maybe. It really depends on your situation.
