NDI Output Lag

Hello all!

Some weeks ago I had to provide gfx for a streaming production. We agreed on using NDI passing to VMIX.
I checked on the caspar server and NewTek scanner that all was correct and VMIX detected correctly the feed.
Once the connection passed trough the production switch instead the gfx started to lag incredibly a lot and at the end was not possible to be used.
After that I read a lot about NDI and switches but I was wondering if you have any tips about hardware setup.
Connected to the same switch I suppose there were 7 camera feeds and the internet backbone.
I would like for the future to warn the producers about what they need to make it work in case they are not aware of it.
Thank you!

These are all coming in via NDI? I heard, that one should not use more than 4 NDI streams over the same network. Personally I have experience using 2, without a glitch.

I actually do not know how their connections were working. I will ask them.

In my experience i can say that…

  1. The 4 ndi streams limit its a good practice to get some headroom over each Giga ethernet link (port). When you use 1080HD you can get about 150 to 200 mb/s. per stream. The ethernet cable and the ethernet board are critical. Also the overall switching capacity in the network is very important. I suggest to use a GigaSwitch with a throughput of 50 Gb/s., manageable with virtual lan feature. Do not use low cost gigaeth switchs. This switchs are bottlenecks and cause latency also.
  2. When you use other software like Obs for example. The NDI pluging for the receiver side has two settings that modify the latency of the received stream. This are [Sync], and it can be “source timing” or “network timing” and the [Latency Mode] and it can be Normal or Low. I guess you may have in Vmix also something like that.
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