Help Reducing Lag with OBS / NDI / TV setup


New Member
We're a church that's streaming and displaying live in sanctuary at the same time. We're having a problem with lag in the live setup, with up to 500ms delay between live and display on the screen.

Attached is our setup, but a verbal walkthrough.
1) We have multiple cameras (2 NDI, one basic webcam) and a presentation software (Proclaim) that sends out an NDI overlay.
2) OBS overlays the presentation onto the cameras and then outputs to live stream.
3) For YouTube, we have an audio delay setup of about 100ms (I forget the exact number) to keep the sound system audio in sync with the video. So there's already a significant delay coming into OBS.
4) For the live screens, usually we just need the presentation slides, but sometimes we want the cameras, so we have a KVM Switch to easily change between direct from the presentation software (Proclaim) or from live stream (OBS).
5) We have TVs both in the worship space and throughout the building. Those throughout the building always receive the live stream (OBS). Those in the sanctuary are on the switch between presentation software (Proclaim) and live stream (OBS).

If there's a 100ms delay coming into OBS, there's about a 400ms delay going from OBS to the screens in the sanctuary.
If we play video directly from the presentation software (Proclaim), there's a 400ms delay to the screens in the sanctuary. So obviously the KVM Switch or the Orei converter is the problem.

Help figuring out alternate setups or better solutions would be appreciated!

We need to reduce the live delay, as a half second off makes it difficult to watch the screen and enjoy what you're seeing (this is used for like when the bells play in the balcony, or for the children's message so those in the back can see, or to display the organist in the balcony).



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Active Member
Nice diagram! If only everyone would do that!
("I know nothing, just copied some random video, please fix my problem with nothing to go on!" And it turns out they have a royal mess of previous forgotten attempts and whatever complicated unnecessary thing that video had them do, to solve a problem that they didn't even have...yet.)

Anyway, that's a lot of boxes in your critical path! You might see if you can reduce that count. Use dedicated cabling if you have to.

We have a very similar system to yours, in the number of cameras and types of destinations, but all except 2 of our video connections are dedicated to just that. Those 2 are:
  • NDI overlay from Proclaim to OBS for lower-thirds, different from the dedicated audience display, which OBS also has a hardware capture of
  • RTSP (probably) from a phone over WiFi to a browser source in OBS, for a fixed on-stage shot
And neither of them are critical for us.
I've attached the latest diagram here. It's slightly outdated, but not by much.

I'm wondering too, if it's worth the expense for you to get a hardware video mixer? OBS does a lot, and it seems to be fine for us and the other rigs that I've built, but if you're getting excessive lag through that step, then you clearly need something different there.


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