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jamesgid
07-30-2017, 06:18 PM
Hi All,

I have been testing and playing with NDI Monitor and am having some very mixed results. Trying to work out what is possible with NDI Monitor and WiFi connections (If you just screwed up your nose in disgust - then you can stop reading now! :tongue:).

I have a 1080p 30fps NDI feed playing on the network. I then have multiple end points (Windows 10 systems) that I am attempting playback on.

All fine on wired end points, and I see network consumption of ~8Mbps in low bandwidth mode and ~40Mbps in high bandwidth mode with 1x NDI Monitor application running. Same throughput observed on WiFi end points (obviously), but I have very bad video glitches when viewed in High Bandwidth mode. Now the main testing is being carried out on an Asus laptop with i7 and 16Gb ram - it's no slouch. It has 802.11AC and I am currently testing network speed between the laptop and router at ~140Mbps to ~250Mbps.

So why would the NDI feed be so choppy if there is plenty of network speed available to the laptop? Any smart ideas?

(And before someone says, just run a network cable - we cannot. The purpose of this testing is so we can eventually have a laptop that is roaming around the building but still receiving an NDI feed. And while it is working in low bandwidth mode, I just cannot see any reason why it shouldn't work in high bandwidth mode).

Side note - Windows based NDI Monitor really needs a low bandwidth toggle option. I cannot use low bandwidth mode and display full screen at the same time. I am currently either running a 640x480 resolution, or using OBS (Open Broadcaster Software) with the NDI plugin installed and previewing full screen the output on the same display.

Thanks.

kanep
07-30-2017, 10:15 PM
There are a few things that might help.

- Having multiple end points is going to be a problem as they are all competing for the same 'spectrum'. Keep this to a minimum, disconnect any clients that you don't need, even having them powered on but not doing anything can have them use up bandwidth and increase latency.
- You might try changing the bandwidth of the access points to 40MHz instead of 20MHz (which is usually the default).
- If you are using WPA, I would recommend setting it to WPA2 and only use AES encryption. Some devices have hardware acceleration of AES encryption.

You would have to test to see of any of those recommendation make a difference, results will depend on the network and the gear connected to it. However, just because you have high bandwidth doesn't mean you have low latency and WiFi in general isn't as good as wired connection when it comes to latency. WiFi tends to be a bit more 'bursty' in its communication. NDI wants a smooth flow of communication.

Another possible solution is to look at a PowerLine adapters instead of WiFi. I got one of these at home because of similar issues you are describing above. I had a WiFi bridge to connect my NewTek demo equipment which happens to be in my basement to the WiFi access point upstairs. While this worked, I had poor results. I ended up putting in two 2000mbit/s PowerLine units and the performance and latency were highly improved. If you go this route, get the fastest PowerLine units available, in my case the units are rated for 2000mbit/s communication speed, but real world performance is about 250mbits/s. From what I've read, PowerLine performance can vary a lot depending the wiring in your building, and I've never read of anyone getting close to the advertised speed, by going with the highest performance you can still have something usable for NDI. It is my understanding that the more PowerLine adapters you have the more the bandwidth is divided up between them, so try to keep it to a minimum number of units, put a switch behind them if you need to connect multiple systems.

It is possible the upcoming NDI 3 might help. One of the new features is multicast, which could allow a signal stream to be sent out to multiple clients. However multicast can require some specific settings in you network gear and if you are using residential class devices, they might not be able to take advantage of this.

Lastly, if you size NDI Monitor to a small window size, it will run in low bandwidth mode and the new NDI Studio Monitor application that will be coming out soon will have a low bandwidth selection.

The final thing to mention is do you really need NDI for this? NDI is meant as a production format and it sounds like you are trying to use it more as a distribution format. While this can work to a point, I think your workflow is pushing it beyond that. A product designed for this like the NewTek MediaDS could produce the streams and allow you to access them in your building using many WiFi clients without issue.

jamesgid
07-30-2017, 11:24 PM
There are a few things that might help.

- Having multiple end points is going to be a problem as they are all competing for the same 'spectrum'. Keep this to a minimum, disconnect any clients that you don't need, even having them powered on but not doing anything can have them use up bandwidth and increase latency.
- You might try changing the bandwidth of the access points to 40MHz instead of 20MHz (which is usually the default).
- If you are using WPA, I would recommend setting it to WPA2 and only use AES encryption. Some devices have hardware acceleration of AES encryption.

You would have to test to see of any of those recommendation make a difference, results will depend on the network and the gear connected to it. However, just because you have high bandwidth doesn't mean you have low latency and WiFi in general isn't as good as wired connection when it comes to latency. WiFi tends to be a bit more 'bursty' in its communication. NDI wants a smooth flow of communication.

Another possible solution is to look at a PowerLine adapters instead of WiFi. I got one of these at home because of similar issues you are describing above. I had a WiFi bridge to connect my NewTek demo equipment which happens to be in my basement to the WiFi access point upstairs. While this worked, I had poor results. I ended up putting in two 2000mbit/s PowerLine units and the performance and latency were highly improved. If you go this route, get the fastest PowerLine units available, in my case the units are rated for 2000mbit/s communication speed, but real world performance is about 250mbits/s. From what I've read, PowerLine performance can vary a lot depending the wiring in your building, and I've never read of anyone getting close to the advertised speed, by going with the highest performance you can still have something usable for NDI. It is my understanding that the more PowerLine adapters you have the more the bandwidth is divided up between them, so try to keep it to a minimum number of units, put a switch behind them if you need to connect multiple systems.

It is possible the upcoming NDI 3 might help. One of the new features is multicast, which could allow a signal stream to be sent out to multiple clients. However multicast can require some specific settings in you network gear and if you are using residential class devices, they might not be able to take advantage of this.

Lastly, if you size NDI Monitor to a small window size, it will run in low bandwidth mode and the new NDI Studio Monitor application that will be coming out soon will have a low bandwidth selection.

The final thing to mention is do you really need NDI for this? NDI is meant as a production format and it sounds like you are trying to use it more as a distribution format. While this can work to a point, I think your workflow is pushing it beyond that. A product designed for this like the NewTek MediaDS could produce the streams and allow you to access them in your building using many WiFi clients without issue.

Thanks so much for the constructive reply Kane.

Most network attached gear is 40MHz, but some is 20MHz. I have some really nice Ubiquiti WiFi Routers that support both. But have not seen a difference between the two for this testing. And yes, WPA2 everywhere. And I am no fan of powerline adapters. Last time I tried them I was getting 5-10Mbps!! Ethernet cable is so cheap - if we have to, we will run it.

When I talk multiple end points, I don't mean they are all running NDI Monitor at the same time. I am only testing one at a time. But have multiple to test different configurations and distances from router.

I did think about latency. Running Ping Tests I see mostly <1ms responses with the occasional 1ms and 2ms responses. So I assumed we were not having latency issues.

I do know about the resizing of the window for for low bandwidth mode. But I do need to display full screen in low bandwidth mode, something that just cannot be done with the current release of NDI Monitor for Windows platform. I am really looking forward to your NDI Studio Monitor application you referred to. Need a beta tester??

And yes, you are totally correct. We are using it for distribution, but only to 2 end points. It is more for monitoring (green room) in a very small livestream environment (with an even smaller budget). So a product like the NewTek MediaDS (as great as it is) just does not fit within this clients budget (sorry). I thought doing it this way would be a quick, easy and cheap solution given the low requirements. So thanks for you input, I greatly appreciate it.