NDI network - wifi problems and solutions?


#1

Hey guys, i’m very happy with NDI implementation, its great for performances that need wireless movable cams, but have some observations and problems with framerates, and would love to learn others experiences / solutions, in particular regarding which networks / routers to use.

I’ve been developing and performing a set that uses three wireless NDI cams (current gen ipod touch). In studio and rehearsal, i can have all three running in SD on its own wirless network, provided by a Google Wifi, or also just using my normal home network, a router provided by Deutsche Telekom. Also using an old Apple Aiport Express works fine. I get stable 24-30 fps framerates with acceptable low latencies, they are mostly equal to wired video inputs, and uses appearantly less CPU on my system, wieghts NOTHING, so a win win for touring.

When touring I’ve been using the Google Wifi. Up until this weekend, all performances have been smooth sailing. However, this weekend, framerates fell to between 0 and 6 per sec and I could use at most one camera, maybe two (one camera seemed to linger around 12 fps, the other between 0 and 6). They never disconnected but often was just a frozen frame. Nothing I did changed anything, the network (I assume) was “clogged”?. System CPU and VDMX was working fine and responsive. This was in a huge public building, but there weren’t a lot of other wireless networks, as far as i could see. No other wireless equipment in use on stage.

The Google WiFi has no “settings” to inspect or change, it is designed to “optimize” the network itself automatically. And I don’t know enough about network tools or setups to be able to figure out what went wrong.

Does anyone have more experience working with NDI, and have tips for “best practices”, either to set things up so this never happens again, or if it happens, a way to find out what the problem is and correct it? Is there anything in MacOs I can do or look into to help figure out why the network is so slow?

Of course now back in the studio, it works fine, i can’t reproduce the problem. But I’ll be touring extensively with this setup so I fear the problem will appear again, and need to find a workaround/solution, or eventually disregard NDI and look for other video inputs (which I’m soooo tired of…).

Thanks for any advice or input or thoughts!


#2

Hey gmm,

I’ve not used Google WiFi at all, so I can’t speak to the robustness of that as a means to work with NDI streams, but here are a few notes that might be helpful:

  • Off the bat I have to say that to get the best results with NDI® it is strongly recommended to connect devices over a network using gigabit ethernet or similar high speed connections whenever possible; I’m sure you are using WiFi because that isn’t an option here, but worth noting for people who come to this thread for tips – use ethernet if you can!!!
  • NewTek provides a free set of useful NDI Tools applications for testing purposes. If at any point you think there is a problem that has to do with VDMX, give these a try to see if they have similar connectivity issues.
  • Some general notes on WiFi…
    • WiFi essentially works over radio waves; this means that physical structures (such as walls, mountains, trees, etc) as well as electrical interference can diminish the range or otherwise degrade the transmission quality.
    • The antennas on most WiFi routers are optimized for broadcasting horizontally – for example, a WiFi router may work very well between rooms that are on the same floor of a building, but will typically not work well between different floors within a building, even if the rooms are directly above / below each other. If this is the case, you can look into directional wifi antennas.
    • Like radio broadcasts, WiFi routers broadcast on different channels (different frequency ranges). In order to avoid conflicts, WiFi routers will automatically negotiate which channels each is using; in some cases routers will let you manually specify a channel to use. When routers switch channels (say because another router appears that conflicts with it) you can get a momentary drop while the router reconfigures itself. The way this is handled might be something that varies between different routers. (it doesn’t sound like this is the case here, but again, worth mentioning for anyone who stumbles into this thread)
  • If you haven’t already done so, I’d also suggest asking on the NewTek forums (https://forums.newtek.com/), particularly if you can recreate the issue using the NDI testing tools. If this is a general issue related to WiFi streaming, the NDI community at large may have some good suggestions!

#3

Hi GGM,

David pretty much covered it, I’m apart of a touring project that uses wifi and OSC commands. Instead of a dropped frames or frozen images, if the single OSC message doesn’t go through, then it messes with the timing of the show. I also defer from using NDI over wifi because of the bandwidth requirements for HD video. In the past for wifi video, I’ve primarily used other wifi IP cams with URL links and MPEG compressions. While it looks much better, NDI can eat up a lot of resources quick.

  • 1 x stream SD video = 20 Mbps
  • 1 x stream 1080p50/59.94 video = 125Mbps
  • 1 x stream 720p50/59.94 video = 90Mbps
  • 1 x stream UHDp30 video = 200Mbps
  • 1 x stream 1080i50/59.94 video = 100Mbps
  • 1 x stream UHDp60 video = 250Mbps

I’m assuming you are using a 2.4GHz connection. While 5G would be faster, its range is also shorter. When I’m working with wifi devices in close proximity and free of obstacles, I’ll use 5GHz if the devices support it.
That being said, I’m also working on a touring project that has been in the works for over 2 years. Wifi was fine while it was in a smaller city or in the studio, but for venues in Philadelphia, D.C., and NYC. I have converted as much of the setup to hardwired ethernet (RJ45) as possible. The main reason is wifi interference. In Philly, there were about 20+ wifi networks floating around. With cross city wifi networks such as ATT, Comcast Xfinity, hidden ones for government operations, cell phone companies, etc. the 2.4GHz band can look pretty ugly. I use wifi analyzer on my android phone when I get to the venue to determine if a 2.4GHz band channel is free. Since most consumer wifi networks are set to auto channel, it is a roll of the dice whether they will switch over to the one you are using an interfere. 5GHz isn’t as bad because of the range limitations, but there is a range of factors that can make any wifi underperform.

Some odd things to think about_-

-Crowd interference or hacking. Ok, the hacking aspect is less likely, but if someone wanted to run a deauth attack on your google wifi router while you are in the space, it wouldn’t take more than a $5 device plugged into a cell phone to do it.: https://github.com/spacehuhn/esp8266_deauther Seriously, it can happen and has.

I’ve also stumbled across a wifi pineapple setup that would auto duplicate my host network name, deauth it, and capture the connection from the Raspberry Pi’s I was using. They were mainly sending OSC data, but the fact that someone set it up in a public space was pretty alarming.

-Stupid cell phones. Everyone seems to have a cell phone these days, some even work with a form of city-wide wifi services that don’t broadcast an SSID, but are on the same channel of your setup and tear it apart as they live stream to their Instagram.

Could the camera’s own wifi be competing with itself? When I use multiple wifi Raspberry Pi’s I make their channels static.

I could think of a few other reasons, but unfortunately, wifi is an overcrowded medium.

You could try to direct your router: https://hackaday.com/2017/11/18/3d-printed-wifi-reflectors-custom-designed-for-the-building/

Hope this helps


#4

Thank you both, David and ProjectileObjects. This is very very helpful, thanks a lot for taking time to share your knowledge and experiences! I have two weeks studio rehearsals now to do art and tech updates, one of the steps is to try more customizable routers, that also gives me better stats and monitoring tools, one annoying thing with the Google Wifi was that its so “simple” there was no way to force units to use 5 ghz (or 2.4 if 5 really was the problematic one). I would really prefer being able to force all units to be on the 5 Ghz connection, the router and devices will be in short distance from each other.

We’ll see. I will follow up in a few weeks with my experiences, notes and decisions, thanks again!