What is NDI HX?
In this video, we review what the NewTek NDI HX actually is. But before we start, just in case you don’t know what the NewTek NDI is, here is a quick explaination: NDI is a high quality, low latency, IP video transmission standard pioneered by NewTek. This standard protocol has been adopted by the live streaming industry in software such as: Wirecast, vMix, LiveStream Studio, OBS, xSplit, StreamStar and the NewTek Tricasters.
Inside this NDI HX review we will be posting quotes from Dr. Andrew Cross the CTO of NewTek. Dr. Cross was on our live show July 21st 2017 (see the full show transcript here). We also hosted a live Q&A session on YouTube and Facebook Live (see full Q&A Transcript here). These interviews uncovered many of the details regarding the NewTek NDI and NDI 3.0 / NDI HX. I personally believe they are the most technical and in-depth resources available on the internet. az
So what is NewTek NDI HX?
NDI HX is the latest “High Efficiency” version of NDI which has been optimized to open up a whole new world of devices using built-in h.264 compression chips. This will eventually allow more hardware devices to support the NDI standard such as the Connect Spark and our PTZOptics cameras. The beauty of NDI HX is the low bandwidth requirements which allow users on simple Gigabit networks the ability to host multiple video streams without tying up to much network traffic.
What does a NewTek NDI Stream include?
How much Bandwidth does NDI HX use?
This answer will depend on the resolution you are stream but in general the bandwidth will hover around 10 MBps for a 1080p60fps stream. As you can see from the chart below a normal NDI stream on your network will consume 100 Megabits per second of bandwidth. NDI HX (high efficiency) will be roughly 10% of a normal of the normal NDI bandwidth. So what is the tradeoff? Will NDI HX look as good as normal NDI? Well Andrew Cross goes into the difference in the quote below:
“…you could be producing a 4k resolution stream on NDI and you could distribute it to your whole company with a hundred viewers at once… you’d get basically perfect quality video, incredibly low latency you know to unlimited number of viewers.”
NDI vs NDI HX
Okay so NDI HX I mean the HX it stands for high efficiency don’t ask me how E became X but it sounds cooler to say HX but. It stands for NDI high efficiency and so it does run low bandwidth it runs in the range of 10 megabits but it but as I’ve said what we’ve done is we’re working specifically with the important vendors like yourselves to start with and you know most importantly because we’re you know at this point we’re still customizing HX to work really well with every device that we support and so I don’t want to promise that the bandwidth is always going to be exactly the same because we want to make sure that the video quality looks great. But it is in the ballpark what we have typically found this at about 10 megabits and maybe slightly above is the point at which it looks as good as I mean it’s imperceivable and even in just terrible footage. That is the point that we that we get to and I should say it don’t you can’t directly compare this maybe with say streaming at 10 megabits because we are we’re doing things that aren’t the same as streaming. The things that we can take advantage of that there others couldn’t so, for instance, and you know I’m really getting into the details here we can run with an incredibly long group of pictures. So, we don’t need iframes, we don’t; we know when we’re connecting and not connecting and so we get control over how the stream is being produced. That wouldn’t normally be the case and so we can do some things to get much better bandwidth than one might possibly norm imagine. Hopefully, (no) it works really, really well. – Dr. Cross
How much latency does NDI HX have?
Roughly 30-50ms (milliseconds) which can be less than a frame depending on the frame rate you are using. This is extremely low latency and un-noticeable during a live production.
So, at this point every device in order to get to low latency, high quality, automatically discovered, full PTZ control, all of those pieces you know our goal is how can we make NDI HX work with a camera that exists today and so we’re working with as many companies as we can and focusing on it you know the really important ones first on collaborating on getting those two pieces working together. And so yes I mean it requires us to sit and tweak and I know that you know like with yourselves we’ve had changes made to the firmware. – Dr. Cross
Does NDI HX use h.264 compression?
Yes, NDI HX uses very high bitrate h.264 allowing users to maintain high levels of quality and the ability to run on existing devices today with customized firmware.
Your cameras (in reference to PTZOptics Camera Models) have h.264 encoders but we’re running high, high bitrate h.264. We’re not running you know low bitrate streaming h.264. So, this means that we can work with in encodes that exists today for instance and it is customized so that you know that there were firmware changes that you’ve made. That allows us to; it’s not just a regular stream we’re doing some clever things on top of that, to manage to get to very low latency, to get to very high quality and to make it actually integrate and work well with you, you know there’s a lot of pieces to putting this together reliably. – Dr. Cross
How is it different from RTSP?
NDI uses an incredibly long run of frames and has the ability to make intelligent decisions based on connections. Therefore NDI does not require the use of I-Frames allowing NDI to reduce latency and improve bandwidth constraints.
The things that we can take advantage of that there others couldn’t so, for instance, and you know I’m really getting into the details here we can run with an incredibly long group of pictures. So, we don’t need iframes, we don’t; we know when we’re connecting and not connecting and so we get control over how the stream is being produced. That wouldn’t normally be the case and so we can do some things to get much better bandwidth than one might possibly norm imagine. -Dr. Cross
Comments from our Facebook User Group
– HX has 50ms latency, that’s not 1 frame, that’s nearly 2 at 30 fps and nearly 3 at 60 fps. I agree it’s not much but let’s tell the truth
– HX’s main interest is wireless use. You have no commercial interest for this (so I understand you do not talk about it) but you could mention it anyway.
– No NDI does not allow only 6 streams on a SWITCH ! I told you this before. You’re confusing SWITCH and NIC ! A full-duplex Gigabit switch has 2 Gbits bandwidth PER PORT.
You should say : a regular PC NIC at 1 Gbits can only transport up to 7 or 8 1080p30 NDI full quality streams. If you work in SD, the number goes to close to 20. Let’s be precise and fair.
– There is no improvement, aka High Efficiency” in “H.264 encoding” as you suggest. The encoding won’t be better: it’s the same chip. The High Efficiency feature concerns essentially the reduced latency.
– Globally you suggest that HX is even better than previous NDI versions, which is not true, but I reckon Newtek is responsable for this. You could anyway say that HX is a low spec codec for easier transport and your explanation for Long GOP is really not good.
– NDI as a new standard for PTZ controls. Maybe, but I highly doubt Sony will ever come to it for example. Sony is developping their own IP standard for video. You should not mention them, unless you have a press release for it.
– 10 Mbits is not an “extremely high bitrate” for H.264 as you say. Most camcorders, even cheap ones, have a minimum bitrate of 15, 20 or 25 Mbits. Good ones go to 50 or even 100 Mbits for recording.
– There won’t be “higher quality” with HX/H.264 encoding in NDI|HX over RTSP. It’s strictly the same stream, apart for latency and auto discovery and multicast support.
Learn more about the NewTek NDI for live streaming PTZ Cameras
